Weight loss diets: the ultimate guide

This guide was written to help you gain a better understanding of how your diet affects the amount of weight you lose (or gain!). I begin by covering various food types & their benefits and finish off by analysing 4 of the most popular weight loss diets available today. The article is fairly long so you may want to grab your favourite drink!

The Basic Principle – Calories In vs Calories Out

Arguably the most important element of any weight loss plan is the diet. We eat in order to gain energy, which is vital for all bodily processes. Just as we can measure how much an item of food weighs using, for instance, grams, we can measure how much energy is found in our foods using calories.

One unit of energy is called a calorie, and describes how much energy it takes to raise the temperature of 1 gram of water by 1 degree celsius. Calories are found in every single type of food. The body uses calories for all sorts of important processes, but those that aren’t used are stored as fat.

This is true of every person who gains weight, and the most important rule for weight loss is to remember that you need to consume fewer calories than your body uses up in order to burn fat. (See out 70+ weight loss tips here).

At rest, the body will burn a large number of calories through normal bodily processes. These include breathing, organ function and repairing & maintaining cells. On average, the male body burns approximately 2500 calories per day, and the female body burns 2000 calories.  This is the basis for male and female recommended daily allowances (RDAs) of calorie intake.

Different food types contain different amounts of calories; protein and carbohydrates contain 4 calories per gram, and fat contains 9 calories per gram (UCLA, 2005). The higher content of calories in fat means that you need to eat less of it to gain the same amount of energy as you would from carbohydrates or protein.

Modern diets contain significantly more fat than the body requires (Cordain et al, 2005) due to the fact that our lifestyles and diets have changed over the thousands of years that modern humans have existed, but our biology has not.

In the distant past, humans had to scavenge and hunt for their food, and diets consisted of significantly more fruit and vegetables than they do nowadays. Calories were burned more easily through everyday activities, and foods high in fat and sugar were scarce.

This scarcity meant that the body evolved to desire them so that they would be consumed wherever possible, because they are excellent sources of energy. Biologically we have not evolved since our prehistoric ancestors were scavenging for food on the African plains, and so we still crave these fatty and sugary foods.

In the modern world, these foods are plentiful, cheap, easily accessible and very appealing to us, and so we over-indulge. This goes some way towards explaining why so many people around the globe are overweight.

Determining How Many Calories You Need


Although there is a set recommended daily allowance of calories for men and women, each person is different. Height, weight, activity levels, genetic predisposition and so forth all determine how many calories an individual needs in order to maintain their current weight.

Information from the University of California suggests that two main factors indicate your calorie requirements: basal metabolic rate and level of physical activity. Basal metabolic rate (BMR) is the energy needed to maintain your body’s basic physiological processes. Both BMR and physical activity require calories, and so the amount of calories you need to consume is very dependent on these two factors.

There are plenty of online calorific need calculators which allow you to determine your calorie requirements, such as the Free Dieting Calorie Calculator.

The Importance of a Balanced Diet

For a healthy diet, the WHO recommends that people should generally reduce fat intake, increase intake of vitamins, minerals, legumes, grains and nuts, and limit salt and ‘free’ sugars (WHO, 2015). Healthcare professionals, dieticians and nutritionists are also commonly found recommending that people consume a ‘balanced diet’.

This is a term which is bandied about all over the place, but it is rarely explained. It is easy to assume that a balanced diet means one low in fat and sugar and high in fruits and vegetables; it is true that modern diets do generally require less fat and more vitamins and minerals, but it is still important to ensure that the diet contains all five of the ‘main’ nutrients in order to maintain a healthy body; fat, protein, carbohydrates, vitamins and minerals.

The body requires different levels of each of these nutrients to influence health and body weight in different ways.



When people begin a weight-loss regime one of the first things many remove is fat, because it is the very thing they are trying to shed from their body. It makes sense that less fat in the diet will lead to less fat in the body, but unfortunately it is not quite that simple. There are two main types of fat; saturated and unsaturated fat. Unsaturated fat is further broken down into polyunsaturated fat and monounsaturated fat.

Each type of fat has a different function within the body. Saturated fat, like all types of fat, provides the body with important energy it needs to function. Research has shown, however, that individual saturated fats have specific functions unrelated to energy production.

– Butyric acid regulates gene expression; in other words, it makes the information found in genes into a useful product, in the form of protein or RNA (ribonucleic acid), which dictate cell function. Gene expression needs to be regulated because if it occurs all the time this can actually cause damage to the body, including cancer.

– Palmatic acid is involved in the regulation of hormones. Like gene expression, the release of hormones needs to be controlled in order to maintain proper function within the body. Too much oestrogen, for instance, can cause mood disturbances, whereas too little can lead to menopause-like symptoms such as hair growth, hot flushes and loss of libido.

– Both palmatic acid and myristic acid are involved in cell messaging and immune function. Cell messaging is important for both conscious and unconscious processes; for instance, in order to move your arm, cells called neurons found in the brain and spinal cord need to communicate with one another to create the movement. Immune function is vital to protect the body against pathogens (viruses, bacteria and other micro-organisms) which can cause disease.

Because of the importance of saturated fat for bodily function, having some in your diet is necessary. The problems with saturated fats come from the fact that they have also been linked to higher levels of cholesterol in the blood, which in turn, have been linked to cardiovascular disease.


Furthermore, saturated fat causes significant weight gain when consumed in excess. WHO (2003) recommend that saturated fat should constitute less than 10% of the total number of calories consumed in a diet. They found, however, that in affluent regions of the globe (i.e. parts of North America and Europe) the intake of saturated fat is in excess of 10% of all calorie intake, whereas for all other regions it is between 5 and 8%. Furthermore, in the UK only 2-4% of the adult population is consuming the recommended amount of saturated fat.

In a study by Rosqvist et al (2014) the dangers of saturated fat are outlined quite clearly. 39 healthy adult participants ate 3 or 4 muffins (made up of either saturated or unsaturated fat) per day for seven weeks. Afterwards their liver fat content, total body fat and total lean tissue was measured using an MRI scanner.

Both groups were found to have gained 1.6 kg in weight, but it was discovered that participants who had consumed the muffins made of saturated fat gained more liver fat, total fat, and visceral fat (fat around the bodily organs). They also showed significantly greater fat to lean tissue ratios than those who ate the muffins made of unsaturated fat; in other words, those on the unsaturated fat muffin diet gained extra lean tissue weight, whereas those on the saturated fat muffin diet gained more body weight.

What this research shows is that although saturated fats are important for certain bodily functions, too much can have a significant negative impact on body weight. The researchers suggested that the reason saturated fat can encourage fat storage in this way is because it might block gene-expression for fat burning and enhance gene expression for fat storage.

As a person living a life where food needs to be hunted and foraged for, this would be a very useful system, particularly in the winter when food becomes more scarce. In a modern day society where sedentary lifestyles are plentiful, however, this process can lead to significant weight gain over a short period of time.

Fortunately, unsaturated fat does not appear to produce these consequences for weight gain; although participants in this study did also gain weight, they gained muscle mass (how this happened will be explained later), which makes fat burning easier. Therefore, their excess weight would be much easier to remove.


Unsaturated fat, as mentioned, comes in two forms; polyunsaturated and monounsaturated fat. Polyunsaturated fat was used in the above study (in the form of sunflower oil), and has a variety of functions within the body which can promote health.

– It can help to reduce levels of LDL (low-density lipidprotein) cholesterol, a ‘bad’ type of fatty deposit which lines the walls of the arteries and causes high blood pressure and other heart problems.

– It provides nutrients which help to develop and maintain cellular structures.

– Oils rich in polyunsaturated fat provide the body with vitamin E, a powerful antioxidant to help fight off free radicals, as well as omega-6 and omega-3 fatty acids which can be beneficial for brain function, growth and development of bodily structures, maintenance of the reproductive system, reducing inflammation and reducing heart disease.

It was mentioned in the research by Rosqvitz et al (2014) that the participants who consumed muffins made with polyunsaturated fat gained muscle mass rather than body fat. The reasons for this are not exactly clear, but research suggests that omega-3 fatty acids may enhance protein synthesis (the creation of protein in cells), which in turn can contribute to increased muscle mass.

Furthermore, it has been suggested that polyunsaturated fats can turn off gene expression in visceral fat which encourages fat storage. As such, visceral fat levels will be reduced.

Although polyunsaturated fats can’t actually help you to reduce weight, they are much healthier for the body in general, compared to saturated fat. As such, polyunsaturated fats are an excellent replacement for saturated fats as they provide many of the same benefits to the body, plus others, and when weight is gained through polyunsaturated fats it is a much safer type of weight gain.

The third type of fat is monounsaturated fat, and some might argue that it is the healthiest of all the fats. As with polyunsaturated fat, it has a variety of health benefits:

– It helps to reduce levels of LDL cholesterol, which will reduce cardiovascular difficulties

– It provides nutrients to develop and maintain the body’s cells

– It may be beneficial at reducing the risk of developing Type 2 Diabetes

As well as these health benefits, monounsaturated fats may actually help with weight loss. Compared with saturated fat, monounsaturated fat is much more likely to be utilised as a slow-burning energy source. This means that you will feel fuller for longer, so you will be less likely to snack or overeat.

Some types of monounsaturated fat (e.g. omega-3 fatty acids) can help the body to burn excess fat, and they can also combat inflammation, which is is often a cause of weight gain in obesity.

Now that you have some information about which fats you should and shouldn’t avoid, there are some foods which can be added or removed from your diet to help you to ensure the food you are eating has a healthy fat content.

Foods high in saturated fat which you should avoid:

– Butter

– Chocolate

– Cheese

– Cream

– Processed meat (e.g. sausages)

– Mince

– Fried potato products e.g. chips

For all of these foods, there are low-fat alternatives so you do not necessarily have to remove these items from your diet. For instance, if buying mince, make sure you choose lean reduced fat mince.

Foods high in unsaturated fat which you don’t need to avoid:

– Fish

– Avocados

– Nuts

– Olive oil

– Seeds

– Peanut butter

– Beans

Although these foods do contain fat, they are ‘healthy’ fat and as such, are not detrimental to your weight-loss plans.

Note: Although unsaturated fats are significantly healthier than saturated fat, they are still fats, and excessive eating may still lead to weight gain.



Protein is associated with muscle gain and so is often avoided when the goal is weight loss. The body requires protein for a massive variety of functions, however, so it should not be removed from any weight loss diet. Hair and nails are mostly made up of a protein called keratin, and protein is also required to build and repair tissue.

Collagen is the main protein involved in tissue repair and helps to keep the skin looking plump and youthful. Protein is also necessary for creating hormones, enzymes and other important chemicals in the body.

The body requires a large amount of protein in order to function effectively, and so it is important to ensure you are consuming enough. What many people on a weight loss regime don’t realise is that protein can actually aid in weight loss, and so shouldn’t be cut from the diet.

In a study of over 1200 adults by Meinert Larsen et al (2010), participants on a low-calorie diet were randomly assigned to consume one of five diets to prevent weight regain. The study found that by increasing levels of protein but retaining the same number of calories, participants were much more likely to complete the study, and their weight loss was maintained.

Another study by Tang et al (2013) found that male participants on a high protein diet lost less lean body mass but equal body weight compared to a no protein diet, in essence meaning that they appeared more toned and muscular than their non-protein counterparts.

Furthermore, research by Azadbakht et al (2013) on overweight female participants found that a high-protein diet leads to weight loss, but that the best diets are those which are also low in fat. High-protein low-fat diets can lead to a greater weight loss and waist circumference than a high-protein diet alone. Nevertheless, high-protein diets without the low-fat element still led to weight loss, and so this study shows that removing protein from the diet is unlikely to improve weight loss.



Carbohydrates are another nutrient that is often avoided during weight loss regimes for a variety of reasons, including the fact that they are significantly restricted in the famous Atkins diet. This diet will be discussed in detail later, but for now I feel it is important to note that it has come under a massive amount of scrutiny. For instance, some research has found that it can lead to tissue and vascular (circulatory) damage (Beissenger et al, 2005), and it may increase the risk of breast cancer, heart disease and headaches (Newman, 2004)

Carbohydrates are converted into sugar by the body to provide the main energy source for most bodily functions. Carbohydrates also have other specific functions, including protecting the body from bowel problems due to the high levels of fibre in them, improving serotonin production (for a better mood), maintaining heart health and ensuring cognitive function is at its peak.

Not only are carbohydrates important for maintaining physiological stability, but they also have a role in body weight. Research by Ma et al (2005) investigated the association between carbohydrates and body weight in a review of data from over 570 participants collected over a period of four years.

The research found that there are different types of carbohydrates which influence body weight in different ways. Specifically, foods with different glycemic indexes (GI) had a strong influence on body mass index (BMI). Glycemic index refers to how carbohydrates influences the blood glucose levels, which can have an impact on energy and mood, and if the levels are too high or too low can lead to some medical issues for those with diabetes.

The research by Ma et al found that foods with greater GI lead to a greater level of insulin production (insulin allows the body to use the sugar consumed in food), as well as greater fat storage. What this suggests is that carbohydrates themselves do not lead to weight gain, but that the type of carbohydrate you consume can influence how the body stores fat.

Foods with low GI which may be the best carbohydrates to consume for weight loss and include:

– Muesli

– Pitta bread

– Spaghetti

– New potatoes

– Oranges

– Fruit loaf

– Tortilla wraps

– Bran

– Nuts

– Brown rice

– Beans

Foods with high GI which may encourage fat storage include:

– Doughnuts

– White rice

– French fries

– Scones

– Watermelon

– Dates

– White bread

– Pumpkin

– Parsnips



Vitamins are some of the nutrients which are best known for their health benefits. Meals like salads and soup which contain a large number of fruit and vegetables are very high in vitamins, and are popular with people attempting to lose weight.

Most foods high in vitamins are also low in calories. Fruits and vegetables have the most vitamins of all foods, but they are also found in other foods such as nuts, beans, fish, chicken and beef. Vitamins come in two forms; water soluble and fat soluble.

Water soluble vitamins are not stored in the body so it is very important to eat foods with a high water-soluble vitamin content. As the name states, these vitamins dissolve in water and so through boiling foods with these vitamins, they are lost through the cooking process. This is why some foods are healthier when they are raw. Vitamin C, the B vitamins and folic acid are all water-soluble vitamins.

Fat soluble vitamins are found in fatty foods and animal products, and are stored in the body so it is not necessary to eat these foods every day. They dissolve in fat, and so are not lost in food when boiled. Because the body stores these vitamins it is possible to obtain too many over time, which can lead to health problems. By consuming a balanced diet, however, it is unlikely that you will have too many of these vitamins. Fat-soluble vitamins include vitamin A, D, E and K.

Vitamins have a wide variety of functions in the body. Vitamin C boosts immune system function and vitamin A helps to maintain good eyesight. The B vitamins and folic acid are important for helping to release energy from the foods we eat and building components for red blood cells which carry oxygen to our organs.

Vitamin D is needed to keep teeth and bones healthy, vitamin E helps to maintain healthy skin, teeth and eyes, and vitamin K is important for blood clotting. For weight-specific functions, vitamin C can help the body to use glucose as energy rather than storing it as fat, and the B vitamins keep the metabolism running at a high level in order to burn more calories.

Vitamins also have antioxidant properties, meaning they help to fight off free radicals which cause damage to cells including DNA. Free radicals are created through a variety of means, including pollution, cigarette smoke, stress and inflammation. Antioxidants can cause a variety of health problems including some cancers and heart disease.



Minerals occur naturally in non-organic substances such as rocks and metals, but they are also very important for the human body. Plantlife provides minerals in the diet, but they are also found in herbivore animal products (i.e. dairy products and meat) through the plant life consumed by the animals.

Minerals have structural properties, meaning they are necessary for building strong bones and teeth, but they also control fluid movement in cells and they help to turn the food you eat into energy. Macrominerals are those which are found in large amounts in the body, and trace minerals are found in small amounts, but they are equally important to maintain a healthy body.

Some well known minerals include calcium and magnesium, but others include zinc, iron, copper, potassium and sodium. Like vitamins, it is possible to consume too many minerals. Excessive sodium levels, for instance can lead to an increase in blood pressure due to high salt levels which cause water retention. High blood pressure can cause cardiovascular problems such as heart attack, so it is important to ensure that levels of sodium are not excessive in the diet.

Although excess minerals can have negative effects on health, they are vital for proper functioning, and so consuming foods containing minerals is very important. Leafy vegetables and animal products are excellent sources.


All five major nutrients (fat, protein, carbohydrate, vitamins and minerals) are vital for maintaining a healthy body. In order to lose weight, many people significantly reduce or completely remove one or more of these nutrients from their diet, but doing this can lead to health problems and may not help with weight loss endeavours.

Many of these nutrients do actually contain weight loss properties when consumed in the correct fashion, so it is important to be aware of this and ensure that even when on a diet, it is healthy and balanced.

Foods to Help with Weight Loss


Research published in the prestigious journal ‘Nature’ by Rolls et al (2014) systematically reviewed all of the research into how portion control influences weight management, and it was found that not only does the amount of food we eat have an influence on the success of weight loss programmes, but the type of food we eat is very important.

Specifically, foods which have high energy density are thought to have a much more detrimental effect on weight management compared to low-density foods. Energy density refers to how many calories are found in a food as a proportion of its weight. For instance, raisins are actually quite calorie dense with 40g containing around 100 calories. These could be replaced with 40g grapes, which only contains around 28 calories.

A food item’s energy density can be worked out by dividing the number of calories in the product by the weight of that product, which is quite a simple way to work out whether the food you are consuming is a good choice for you.

Some low density foods include skinless chicken breast, tuna canned in water, shellfish, most fruits and vegetables such as apples and celery, egg whites, soup, jacket potatoes, low fat yoghurt and beans. As well as eating low-density foods, there are specific food items which have benefits for weight loss.

Blueberries have been labelled a superfood because of the multitude of health benefits they provide, and one of these might be that they influence how the body processes fat and sugar. Research by Seymour et al (2011) assessed the influence of blueberry powder on rats fed either a high or low-fat diet.

They found that in both diets there was reduced body weight & liver fat, and blueberries influenced the process of fat oxidation. Oxidation describes the processes involved when burning fat and sugar for energy, and this study found that blueberries may improve this process to help the body burn these substances more easily.

Grapefruits (and especially grapefruit juice) can reduce the amount of energy the body stores as fat, according to research by Chudnovskiy et al (2014). Mice were fed either a high or low fat diet, and half were also given grapefruit juice. It was found that the mice who had consumed the grapefruit juice and ate the high fat diet gained nearly a fifth less weight than the mice on the high-fat diet who hadn’t consumed grapefruit juice.

The effect wasn’t found for those on a low-fat diet, but the reasons for this are unclear. This animal evidence is backed up by research in humans, who show moderate weight loss and significant waistline circumference reduction after adding half a grapefruit to each meal on a normal diet for 6 weeks (Dow et al, 2012)

Hot chilis and peppers can help with weight loss because they contain a chemical called caspaicin which triggers faster functioning of the metabolism. A faster metabolism means more calories are burned, leading to weight loss. Caspaicin also reduces cravings for salty, sweet and fatty foods in people who don’t consume them regularly, according to research by Ludy and Mattes (2011), and what’s more is that only 1g of pepper is needed for the effect to occur.


Almonds are a great healthy snack choice because they can help to reduce abdominal mass and waist circumference when compared to a calorie-matched, equally high-carb snack (Berryman et al, 2015)

Oily fish such as salmon contains omega-3 fatty acids which encourages the body to burn excess fat. Fish oils also help to reduce the levels of leptin, a hormone which has been linked to a slower metabolism and weight gain. Reductions in leptin allows the body to utilise the energy from foods more efficiently, and help weight loss to occur.

Eggs are an excellent choice when trying to lose weight, as demonstrated in a study by Vader Wal et al (2005). Participants were asked to eat a breakfast based on either two eggs or a bagel, both of which were calorie matched. Their eating habits were assessed throughout the day, and it was found that those who ate the two eggs consumed a whopping 417 fewer calories over the next 36 hours, felt more satisfied with their meals and ate less food during their meals as a result.

Although eggs don’t have any specific weight-loss qualities, this study shows that they are fantastic as a way to ensure that your body is being provided with sufficient energy to get you through the day without feeling the need to snack and overeat.

Useful Dieting Practises


It’s all well and good knowing what food you should and shouldn’t include in your diet, but for many people eating healthily isn’t enough. No matter how many salads they eat, the weight just isn’t coming off. This may not be anything to do with the diet per se, but behaviour surrounding eating might have an impact on how your body reacts to your food intake.

There are a few practices which might help to ensure that your healthy diet is giving your weight loss regime the best chance of success.

Eating in moderation

One of the biggest problems some people have when dieting is that they are eating large portions of food which isn’t necessary, and means they are consuming many more calories than they need to. Most people will not be aware of how large their meals should be, and what the proportion of different nutrients on a plate should be.

According to the American Heart Association, there are a variety of portion sizes for different types of food per day. Based on a diet of 2000 calories a day, there should be 6-8 servings of grains per day (including bread, cereal and rice), 4-5 servings of vegetables, 4-5 servings of fruit, 2-3 servings of fat free or low-fat dairy products, no more than 6 oz lean meat, poultry and seafood, 2-3 servings of fats and oils, 4-5 servings of nuts, seeds and legumes a week, and 5 or fewer servings of sugar a week.

They also explain what a serving of each food type consists of:

– Grains = 1 slice of bread, 1 oz dry cereal, 1/2 cup (105g) cooked rice/pasta

– Vegetables = 1 cup (75g) leafy vegetables, 1/2 cup (75g) chopped raw or cooked vegetables

– Fruits = 1 medium fruit (about the size of a baseball), 1/4 cup (40g) dried fruit, 1/2 cup (125ml) fruit juice

– Dairy = 1 cup (250ml) milk, 1 cup (266g) yoghurt, 1.5oz low fat cheese

– Lean meat, poultry and seafood =  3 oz cooked meat, 3 oz grilled fish

– Fats and oils =  1 tsp soft margarine, 1 tbsp mayonnaise, 1 tsp vegetable oil, 1 tbsp regular dressing, 2 tbsp low-fat or fat-free dressing

– Nuts, seeds and legumes = 1.5 oz nuts, 2 tbsp peanut butter, 1/2 cup (75g) beans

– Sugar = 1 tbsp sugar, 1 tbsp jam, 1 cup (250 ml) lemonade

Many countries have their own recommendations, but most are similar to these American recommendations. The Australian government has their own recommendations, and although the UK government does not have up-to-date recommendations, Bupa UK has provided some suggestions and the NHS has provided an ‘eatwell plate‘ to show the proportions of different foods one should eat in a day.

1/3 should consist of fruits and vegetables, 1/3 should include starchy foods, and the remaining third should be made up of equal portions of dairy products and non-dairy sources of protein, with a small amount left over for foods and drinks high in fat and sugar.

These various guidelines are a useful tool to compare to your current diet, but it is important to be aware that each person is different, and what works for one person may not work for another. For instance, if you exercise regularly, your intake of protein may be increased compared to somebody who lives a fairly sedentary lifestyle.

What is important to remember is that overeating will lead to weight gain, and in order to lose weight, you must burn more calories than you consume.

A longitudinal study by Dutch researchers Walthouwer et al (2015) assessed psychosocial predictors of portion control and how awareness of dietary behaviours can encourage eating in moderation.  They found that half the participants in the study (approximately 170 people) were unaware of whether or not they ate in moderation.

They also discovered that eating in moderation only occurred when participants were aware of their normal dietary behaviours, the perceived risk of overeating, and the influence of societal factors such as social pressure. Furthermore, they discovered that participants who were aware of their dietary eating behaviours consumed significantly fewer calories per day than those who were unaware.

What this study shows is that being aware of what you eat can have a really big influence on dieting success. It may seem like an odd thing to say – surely one is always aware of the food they are consuming? This is not actually the case.


In modern day societies where people mostly eat whilst performing another task such as working, watching TV, talking and so forth, these distractions can lead to a very dramatic increase in calorie intake. Thankfully, awareness of portion control can be improved, as shown by research conducted in the Netherlands.

In an intervention by Poelman et al (2014), over 270 overweight participants were allocated to either an intervention or a control condition. The intervention condition received a ‘PortionControl@Home’ online intervention programme which involved four elements to help people with portion control; a portion size awareness tool which taught participants about the importance of portion control, portion control strategies, a cooking class to teach participants how to cook food which is lower in calories and appropriate serving sizes, and a ‘home-screener’ which assessed the home environment and elements of that which might influence eating behaviour (e.g. visibility of food).

The control group were asked to behave normally, and were given the intervention programme after the study was completed.

The study found that after three months of the intervention programme, those in the intervention group had significantly better portion control behaviours than those in the control group, and that this portion control behaviour had a direct effect on weight loss.


The amount of food you eat is clearly very important when trying to lose weight, but so is when you eat. In the last few years, research has become more heavily invested in timing, rather than type, of food consumption. What the studies have found makes for very interesting reading.

Many of the body’s processes occur as a result of one’s body clock, or circadian rhythm. The circadian rhythm dictates the timing of bodily processes as a result of light in an individual’s environment. Bright lights will trigger certain circadian processes, whereas darkness will trigger others.

The process most well-known for being controlled by the circadian rhythm is sleep. Two processes ultimately rule our need to sleep; the circadian rhythm, and a sleep/wake homeostasis system. In a healthy sleep pattern, the sleep/wake homeostasis system builds up a sleep pressure over a prolonged period of wakefulness, and allows enough sleep to occur at night to enable us to feel refreshed in  the morning.

The circadian rhythm dictates the timings of sleepy and alert periods throughout the day; adults generally have stronger impulses to sleep between 2am and 4am, and between 1pm and 3pm.

The circadian rhythm is controlled by a cluster of cells called the Suprachiasmatic Nucleus (SCN), found in the hypothalamus which respond to light and dark signals. The circadian rhythm is important because it dictates when certain hormones are released; a dark environment will lead to a greater release of melatonin, which causes sleepiness.

Disruption in the circadian rhythm, for instance when flying through different time zones, can cause problems for these bodily processes, because there is a conflict between the time it actually is, and the time your body thinks it is. This is why many people experience jet lag; their body is telling them it is time to sleep, but light is stimulating circadian processes which keep them from sleeping.

In modern day societies, we are surrounded by bright lights well into darkness. In the winter when days tend to be shorter and darker, we use unnatural lights to illuminate our environments beyond the natural daylight times, which can alter circadian processes.

Food intake and circadian rhythms are associated because, as stated in a paper by Froy, the circadian rhythm is responsible for most metabolic processes. As has been previously mentioned, the metabolism burns calories found in food as energy, to ensure the body is working to its maximum potential.


A disruption in circadian rhythms can lead to a disruption in metabolism, which in turn can reduce the amount of energy burned in the body. Excessive light during the evenings and prior to sleep are a common reason for disruptions in metabolic processes.

Animal studies have found that there is indeed a connection between circadian rhythms and weight gain, and that when you eat can have a significant impact on weight loss. A study by Fonken et al (2010) examined the effects of different light-levels at night on body mass in male mice.

There were three groups of mice used in the study; those housed in a continuous bright light (BL) environment, a dim light cycle (DL) environment, or a standard (S) light/dark cycle of 16 hours daylight to 8 hours darkness. Calorie intake and activity output were the same across the groups.

The researchers discovered that after 8 weeks in the experimental light conditions, mice in the BL and DL conditions had significantly higher body masses and reduced tolerance for glucose, compared to those in the normal conditions. Furthermore, feeding behaviour was also disrupted. All three groups consumed the same amount of calories, but those in the DL condition ate significantly more food during the daytime compared to mice in the S condition.

This food consumption was positively correlated with body mass, meaning that as more food was consumed during the daytime, body mass also increased. This weight gain is attributed to disrupted internal metabolic activity due to light conditions. Even low-lighting was enough to disrupt this process, which has significant implications for humans living in generally ‘bright’ environments.

Similar results were found in research by Arble et al (2009) who found that mice fed a high-fat diet during daylight gained significantly more weight than mice fed the same food at night. Mice are nocturnal, and generally consume around 80% of their calories at night.

Simply by disrupting the time of food consumption, mice gained on average 7.8% more fat than those who fed at the ‘normal’ time.

Studies performed in human subjects have supported the results found in this animal research. For instance a 20-week study by Garaulet et al (2013) investigated the impact of consumption time on weight loss in 240 participants undertaking a weight-loss programme.

Participants were grouped as either ‘early’ or ‘late’ eaters based on questionnaire responses (ate lunch before or after 3pm respectively) and their weight was measured once per week before and for the duration of a weight loss program. The program involved recommendations of nutrient consumption, nutritional education, physical activity and cognitive behavioural techniques to tackle cognitions around food consumption.

The researchers found that participants who ate later in the day lost less weight than those who ate earlier, and the weight they did lose was lost more slowly. Energy consumption, nutrient consumption, appetite hormones, sleep duration and energy expenditure were all similar across both groups, suggesting that only the time of consumption had an impact on weight loss.


Late eaters also tended to have less energetic breakfasts and skip breakfast more frequently than early eaters. This may mean that their metabolism was not ‘kick-started’ by food consumption earlier in the day, and so they burned fewer calories than those who consumed breakfast.

In ‘evening-type’ people such as those in this study, it has been suggested that they have a delayed circadian rhythm which can lead to a higher ability to gain weight, and less ability to lose weight (Garaulet et al, 2012).

This research all seems to indicate that eating later in the day and having disrupted circadian rhythms due to light exposure at night can lead to significant weight gain, and more difficulty when trying to lose weight. This evidence is further compounded by a study by Adamo, Wilson, Belanger and Chaput (2015) who found that even small differences in bedtimes can influence calorie intake.

Specifically, participants who had later bedtimes (11pm) consume approximately 27% more calories compared to people with earlier bedtimes (10pm), and they also spent more time watching screens, which can disrupt the circadian rhythm.

A recent review by Berg and Forslund (2015) has summarised all the evidence for timing of food consumption and its link to obesity, and has found that unplanned snacking and consuming large amounts of calories towards the end of the day are unfavourable for weight loss attempts.

Avoid Skipping Meals

Skipping meals is a behaviour many people adopt when trying to lose weight, because they hope that by consuming fewer calories their bodies will be forced to burn body fat for energy. Whilst it is true that consuming fewer calories will lead to fat burning in theory, having prolonged periods of time without any energy consumption can have consequences which ultimately hamper, rather than help, weight loss attempts.

Some of these consequences include sugar cravings due to low blood sugar levels, over-consumption at the next meal, and a slowing of metabolic processes.

A longitudinal study (Neumark-Sztainer et al, 2012) of over 10 years assessed dieting and unhealthy weight control behaviours in adolescents, and found that skipping meals actually led to a large increase in BMI over the ten year period (an increase of 4.14 for females and 4.83 for males).

An increase in BMI of four is very dramatic –  there are only 6.5 points between the low end of healthy and overweight, and just 5 points between overweight and obese – so this study clearly shows that skipping meals can be quite severely damaging to your health, and is not a viable option for weight loss.

Popular Diets

For many years doctors, scientists and dieticians have developed a wide variety of diets which all claim to help you to lose weight. If dieting is the path you choose for weight loss, it can be very difficult to know which diet will work best for you.

This article will take you through some of the more popular and well known diets, to help you decide whether any of them might be right for you. Both the pros and cons of each diet will be discussed to provide you with a balanced and unbiased argument.

Atkins Diet


The Atkins Diet is perhaps the most well known and most controversial diet. The original version of the Atkins diet was developed in 1972 by Dr Atkins, and works on one basic principle; when you control your carbohydrate intake, you burn fat. The body converts carbohydrates into sugars, which then enter the blood where cells absorb them to burn for energy. Both fats and sugars are used for energy, and so by significantly reducing the amount of sugar in the diet the body must burn fat.

The diet is popular for a few reasons, but one of the most compelling aspects of the diet is that calories do not need to be controlled; as long as you aren’t eating many carbohydrates, you can eat as many calories as you like (including as much fat as you want).

You also eat frequently during this diet (every two to three hours) and it is claimed that exercise will not make a difference to your weight loss goals so you do not need to incorporate it into your lifestyle. Fortunately, they do acknowledge that exercise is very important for other health reasons.

The diet, named Atkins 20, has four main phases.

During the Induction Phase, the goal is to kick-start your weight loss. For a minimum of two weeks, you are instructed to consume only ‘foundation vegetables’, which include leafy greens, broccoli, cauliflower and asparagus, proteins, healthy fats, most cheeses, and nuts and seeds. You are also asked to eat between 20 and 25 g net carbs each day.

Net carbs are the amount of carbohydrates in a product minus dietary fibre and sugar alcohols (if present). Net carbs, therefore, are the carbs that ‘significantly impact your blood sugar levels’ according to the Atkins diet. It is suggested that these 20g net carbs should mainly come in the form of foundation vegetables. A full list of acceptable foods for the first phase of the diet can be found here.

The second phase (Balancing) aims to slowly re-introduce carbohydrates into the diet until you find the right balance of nutrients for you which still allows you to lose weight. You should stay in this phase until you are within 10 lbs of your goal weight. You should gradually increase your carb intake by 5g over a number of weeks depending on your metabolism and weight loss goal. A list of additional carbs to add to your diet can be found here.

Phase three, the fine-tuning phase, is all about adding in the remaining acceptable carbs into your diet and assessing how many you can eat whilst still maintaining weight loss. This phase should be continued until you have reached your goal weight and maintained it for 1 month. Daily net carb intake can be increased by 5 or 10g over whatever timescale you wish as long as you ensure weight loss/ goal weight maintenance is continuing.

If you find that you ‘plateau’ before you have reached and maintained your goal weight, simply reduce your net carb intake by 10 grams and assess whether that makes a difference. The remaining acceptable carbs can be found in this list.

Phase four is know as Lifetime Maintenance. This is an ongoing phase where you continue to eat as you have been in phase 3, and is all about maintaining your current weight. If weight fluctuates, you should adjust your carbohydrate intake accordingly. Throughout the diet you should have introduced each new carb one by one, which will allow you to assess which ones work best for you. This means that once you reach the lifetime maintenance phase of the diet, you have a good working knowledge of which sorts of carbs are best for you and which might cause you difficulties.

The Atkins website contains maintenance tips for each of the four phases of the diet, along with support when the diet doesn’t go to plan. There is also a more modern version of the plan called Atkins 40 which is recommended for people who have a small amount of weight to lose, who feel they require more variety in their diet (a notable critique of the original diet is that it is too limiting in variety), or who are pregnant or breastfeeding.

In the Atkins 40 diet, all food groups are available, and you begin by consuming 40g carbohydrates a day rather than 20g. You are also instructed to consume between 2 and 4 servings of fat per day, and three 4-6 oz servings of protein. A daily food-type plan and acceptable foods can be found here.

The diet can be successful for many people because it doesn’t involve calorie counting, there are specific foods which should and should not be eaten (eliminating choice can be very helpful for people with low self-control), and the amount of carbohydrates in the diet is gradually increased after the initial weight-loss stage, which helps to increase the balanced nature of the diet.

There have been a very high number of studies which have outlined the benefits of low-carb diets for weight loss. For instance, a meta-analysis by Normann et al (2006) of five randomised control trials (a gold standard trial type in scientific research) found that low-carb diets which do not restrict calorie intake appear to be more effective at reducing weight at six months, and equally effective at 1 year compared to low-fat calorie controlled diets.

This suggests that the basic formula around which the Atkins diet is built may hold some truth. One small note worth making regarding this study is that one of the researchers’ salaries was partly provided by the Atkins foundation, so researcher bias cannot be ignored when interpreting these results.

The Atkins diet has been critiqued for increasing the risk of cardiovascular disease and osteoporosis (O’Keefe and Cordain, 2004) and this meta-analysis does suggest that these concerns may have some truth to them. Low-carb diets were found to be less effective at reducing LDL (low-density lipoprotein) cholesterol compared to low-fat diets, which is strongly implicated in the development of atherolsclerosis.

This is the build-up of fatty deposits on artery walls which leads to many cardiovascular problems, such as heart attack and stroke. Neither low-carb nor low-fat diets showed any benefits for the risk factors of cardiovascular problems, including high blood pressure and lipid levels.

Despite the criticisms of the diet, it does appear to be an effective weight loss tool. The problem with the diet is that the mechanism by which weight is lost is unclear. Some claim that it occurs because participants feel more full than those on low-fat diets (O’Keefe and Cordain, 2004).

Having adequate levels of protein and fat (for instance by consuming red meat, which is often not allowed in low-fat diets) ensures that calorie intake is sufficient for hunger to remain at bay. These foods have superior satiety properties, meaning that by eating these foods you will feel fuller for longer. This may make it easier to reduce calorie intake whilst remaining satisfied with food consumption, which in turn can lead to weight loss.

This diet is also critiqued for being unbalanced, and as such, goes against most healthy eating advice. It may also be unsustainable in the long term due to the significant dietary restrictions it contains, even post-weight loss.

Furthermore, it is important to remember that by undertaking this diet, you are giving money to the Atkins company. They instruct you to only consume Atkins labelled products because they have been tailor made to fit in with Atkins restrictions. They also advertise recipe books and dieting books which are expensive and ultimately are extremely profitable to the company.

Nevertheless, this diet is successful for some people, but you must ensure that if you wish to try it out, you do so sensibly, and are vigilant about your health and how the diet may be affecting it.

5:2 Diet


The 5:2 diet is perhaps the ‘trendiest’ diet on the market at the moment, and has some elements which make it extremely appealing to those wishing to lose weight in a simple way, which is easily maintained. It involves two days of fasting, and five days of eating normally; this is known as ‘intermittent fasting’.

On a fasting day, you are still allowed to eat, but women must only consume 500 calories, and men 600 calories. On the other five days, you must eat no more than 2000 calories. Other than these simple rules, there is nothing else to do.

There are no food types which are restricted, and all food is allowed. It is a simple diet, but it has been shown to be extremely popular and very effective. There are even claims that it can reduce blood pressure, insulin resistance, and can prevent Alzheimers disease (although all studies providing evidence for this have used animal models rather than human participants, such as Kumar et al (2006).

The 5:2 is a relatively new diet, and so research into its effectiveness is somewhat limited. Nevertheless, some studies have been conducted and the results are promising. Compared to daily calorie restriction, intermittent fasting has been shown to be an alternative which not only promotes weight loss, but also reduces the risk of type 2 diabetes in overweight populations (Barnosky et al, 2014).

Furthermore, when combined with carbohydrate restriction, and when allowing for protein and fat consumption, intermittent fasting leads to greater weight loss than simple calorie restriction (Harvie et al, 2013). These results are also able to be maintained for at least 1 month after goal weight is reached.

A review conducted in 2014 by Johnstone further supports intermittent fasting as a viable option for weight loss, as it is simple to follow and maintenance of weight loss seems feasible to achieve. One problem Johnstone outlines is that on the fasting days dieters do become very hungry, but that may vary depending on the foods the dieters choose to eat on their fasting days.

Eggs, for instance, are known for their ability to aid in feelings of satiety due to their high levels of protein, and one egg only contains 89 calories. Salads are also extremely low in calories and so can be consumed in large amounts on fasting days to help combat feelings of hunger. Eating foods which are low-density (in terms of energy; see above) may be a good way to ensure that during fasting days, hunger is kept at bay.

There are a number of different ways to conduct a 5:2 diet. The ‘standard’ version means that from when you wake up to when you go to sleep you consume no more than 500 calories (600 for men). Another way is to go from one meal to the same meal the following day; in other words, fast from breakfast to breakfast, lunch to lunch, or dinner to dinner.

This alternative way of fasting may be easier for those who struggle with consuming so few calories. This is because the fasting period is just 24 hours rather than the approximately 32 hours of the standard fasting period (when you add on time asleep to a full day of fasting). It is unknown, however, which type of fasting is most effective for weight loss and for the other health benefits claimed by the 5:2 diet.

Furthermore, because it is a relatively new dieting technique, long-term studies into the lasting effects of intermittent fasting are unknown.

Another problem with this diet is that the 75% reduction in calorie intake for the two fasting days appears to be a fairly arbitrary reduction; there is little clear evidence to back up the claim that 75% of calories must be reduced for the effects to be seen.

Before undertaking this type of diet with extreme calorie restriction, it is important to be aware of how many calories your body requires to be healthy. If you are short of stature for instance, you will require much fewer calories than someone significantly taller than you who weighs the same.

Therefore, your calorie requirements will be very different, and significantly reducing them may cause you to develop health problems. Speak to your GP before undertaking a diet with extreme fasting elements to it.

Paleo Diet


The Paleo diet is based on the premise that there is a mismatch between our bodies and our diets, and that this mismatch is the cause of many health problems, including obesity, heart disease and diabetes. Also known as the Caveman diet, it consists only of food which can be hunted or gathered.

This includes fish, seafood, meat, berries, nuts, seeds, eggs, fruits and vegetables. There is no specific structured Paleo diet, but most encourage lots of meat consumption and extremely limited or no consumption of dairy, salt, potatoes and cereal grains such as wheat.

This diet is positive in some ways because it encourages consumption of natural foods which are nutrient rich. On the other hand, eliminating grains, legumes and dairy can significantly reduce the availability of important nutrients necessary for health.

One benefit of the Paleo diet is that it works on an 85/15% principle, meaning that 15% of the time you don’t have to follow paleo rules. That allows you to occasionally eat processed food, potatoes and dairy whilst still accessing benefits to health.

Unlike other diets, the Paleo diet doesn’t specifically focus on weight loss – it is just one of a myriad of health benefits claimed to be resultant from this type of eating. Other benefits claimed include reductions in the risk of developing heart disease and diabetes, improving brain health, better intestinal health and reduction of inflammation.

Research into the Paleo diet suggests that it can lead to some health benefits. For instance, it has been shown to reduce blood pressure, insulin levels, and total cholesterol levels (Frassetto et al, 2009) This study only consisted of 9 participants, however, so the results cannot be easily generalised to the standard population.

A meta-analysis of seven studies by Young (2014) found that the diet does seem to be beneficial for weight loss. Specifically, short-period (3-15 months) studies of the Paleo diet were found to be significantly more effective at reducing weight compared to all other diets studied.

The effects were best for obese participants, and it was found that dieters on the Paleo diet reported much greater feelings of satiety compared to those on other diets. This research suggests that for those who are obese, the Paleo diet may be a successful way to quickly reduce dangerous levels of body fat.

Despite the potential benefits of the diet, very little research has been conducted. The diet has also recently come under scrutiny because proponents attempted to release a recipe book aimed at feeding babies and toddlers, which was thought to be potentially dangerous to a child’s health.

Before this diet can be promoted, much needed research must be conducted to assess whether it does actually lead to health benefits, and who exactly should be consuming this sort of diet.



WeightWatchers is a global organisation with over 50 years experience of helping people to lose weight. The diet plan works on a points system, where no food is off limits as long as it allows you to remain within your personalised ‘ProPoints allowance’.

ProPoints are assigned to different food types depending on protein, carbohydrate, fat and fibre content, and personal allowance is based on demographic information including BMI and gender. Each dieter is given additional ProPoints each week which can be used for unexpected or necessary deviations from the diet plan, such as parties and other events. These additional points can be saved up for special occasions or used in small amounts as and when you choose.

WeightWatchers is positive in many ways, but one of the strongest points in its favour is that the diet is completely tailored to you, but is always balanced and healthy. It takes into account medical restrictions such as gluten free diets, as well as personal preferences such as a diet high in carbohydrates.

The diet also attempts to emphasise the importance of living an active lifestyle through awarding active dieters with ‘activity ProPoints’ which can be used to incorporate treats and snacks into the diet.

Alongside the diet, support can also be found through WeightWatchers meetings and/or the online community. Meetings occur all over world (there are over 40,000 meetings globally) and are an excellent place to find support for your diet, share success stories and learn how to diet in a healthy and successful way.

The online community includes the ability to chat immediately with a member of the WeightWatchers team if you require advice or assistance, and also includes hundreds of recipes, meal plans, guides and even includes an app to help you to track your specific plan.

Although the diet is extremely comprehensive and can be tailored to individual needs, dieters must pay for the ability to undertake this diet; the diet, the meetings and the online service all require payment prior to use, indicating that along with helping dieters to lose weight, WeightWatchers does require you to part with money.

Nevertheless, research has indicated that when followed correctly, the diet can have extremely successful outcomes. For instance, when compared to standard care for obese individuals in Australia, Germany and the UK, participants who took part in WeightWatchers for 12 months lost significantly more overall body weight and their waist circumference was significantly reduced (Jebb et al, 2011).

These participants also showed significant improvements in insulin levels and the ratio of total cholesterol to HDL (good) cholesterol. Completion of the 12 month programme was also more likely for participants undertaking WeightWatchers compared to standard care (61% and 54% completion respectively).

In the UK, an audit by Ahern, Olson, Aston and Jebb (2011) was conducted for an NHS WeightWatchers referral scheme involving nearly 30,000 participants. They found that on average participants lost 3.1% of their initial weight, and a third of all patients lost at least 5% of their initial weight. This is a clinically significant amount which leads to an improvement in health.

Furthermore, multiple studies in the UK specifically have also found that WeightWatchers is a cost-effective treatment for obese and overweight individuals. For instance, in a study by Fuller et al (2013) of over 770 participants it was found that compared to standard care, WeightWatchers was extremely cost effective.

In Australia and the UK, the cost per kilogram of weight loss was much lower for WeightWatchers compared to standard care. This remained so when taking into account that both participants attended two to three times more meetings than standard care, and also their travel costs associated with meeting attendance.

Despite the positive research which support WeightWatchers as a weight loss plan, it does incur costs, and so it may be worthwhile trying out some of the free diets before spending money. Nevertheless, it seems that those who use WeightWatchers do find that they lose weight, and it is a program which doesn’t require calorie counting or a significant reduction in the types of food you are allowed to eat.



This list is just a snapshot of the hundreds of diets available, but gives a good overview of some of the more popular dieting techniques and theories. When choosing whether to follow a diet, and which to follow, it is important to take into account how much weight you wish to lose, whether you will benefit from support from other people (e.g. through Atkins or WeightWatcher style community meetings and online resources), what your food preferences are, what your current diet is and how long you wish to be dieting for.

As a general rule, diets which promise to help you lose weight quickly will most likely fail to provide you with a healthy and balanced diet. Furthermore, once a goal weight has been achieved on these sorts of diets the dieter tends to begin to eat normally. If you do this in the wrong way, for instance too quickly, you may undo all of the success you have achieved with the diet.

Dramatically increasing calorie intake without allowing your metabolism to slowly adjust can result in significant weight gain, which may lead to another attempt to diet. A cycle like this can result in ‘yo-yo’ dieting where weight continually fluctuates as a result of changing eating habits and metabolic processes.

A healthier approach is to find an approach which you feel you can maintain in the long-term and which provides your diet with a balanced nutritional profile to ensure your body is getting all the nutrients necessary for health, whilst still allowing you to lose weight at a slow but steady pace.

Diets which have elements of education regarding calorie control, portion size and nutrition are beneficial because once you decide to stop dieting you will have the information at your disposal to ensure you do not regain unwanted weight.

Even better, however, are ‘lifestyle changes’ which allow you to alter your eating without viewing the change as ‘going on a diet’. Rather, it is an alteration of your current lifestyle habits. These are plans which can be maintained for the foreseeable future, and as such have ‘damage control’ properties to tackle any weight gained without being unnecessarily restrictive. They contain a varied nutritional profile which ensures meals are kept both interesting and healthy.


I hope this article helped broaden your knowledge on how your diet can affect weight loss. I would like to wish you all the best in your weight loss journey. Stay healthy, my friend!

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