Weight loss supplements – do they work?

Alongside exercising and adjusting one’s diet, supplements exist which claim to help with weight loss. There is a huge market for dietary supplements but because of this it can be very difficult to know which ones work and which are simply money-making schemes.

Unlike other ‘medicinal’ products, supplements are not regulated. They do not need to be ‘FDA’ approved (Food and Drug Administration) in the USA. This means American consumers are particularly vulnerable to being hoodwinked into buying expensive products which actually hold no health benefits.

In Western Europe in 2009 alone, the slimming products industry made over £900 million (NHS, 2011). This does not mean that all supplements are created simply to make a profit, but these figures are important to be aware of when considering adding supplements to your diet; if you are not careful, you may be spending money on something which holds no benefit to you whatsoever.

A supplement is any product which “contains a dietary ingredient intended to add further nutritional value to the diet” (FDA, 2015). They can contain a variety of ingredients including vitamins, minerals, herbs and amino acids, and come in many forms such as in a pill, a capsule or a powder.

Different supplements have different functions, but there are some broad supplement categories. Some have medicinal properties (and are often called ‘herbal’ or ‘botanical’ supplements), and others ensure the consumer has sufficient nutrients.

These supplements are particularly popular with people who have strict diets which cut out food groups. Supplements have also been designed which aim to help consumers to improve their appearance, whether it tackles skin, hair, nails or body weight.

There are a wide variety of dietary supplements which claim to encourage weight loss. Most are proposed to work through either boosting the metabolism, blocking the absorption of dietary fat, or promoting satiety.

Effectiveness of Common Weight Loss Supplement Ingredients

1. Bitter Orange


Bitter orange, also known as synephrine, is proposed to work by increasing ones metabolism and the process of breaking down fats (lipolysis). It also contains a function as a mild appetite suppressant.

It is difficult to assess the effectiveness of bitter orange as a weight-loss tool because it is often combined with other ingredients, meaning that it’s properties cannot be assessed in isolation.

Nevertheless, research must be conducted to substantiate claims made by supplement manufacturers, and in 2012 Stohs, Preuss and Shara carried out a review of the human studies involving bitter orange.

Of the 23 studies reviewed (assessing a total of 360 participants) it was found that both when taken alone or combined with other products, bitter orange led to an increase in metabolic rate and energy expenditure.

Furthermore, modest weight loss was found when the supplements containing bitter orange were taken for 6 to 12 weeks. The review concluded that although results were promising, more long-term and well-controlled studies are required before efficacy can be determined with more confidence.

As well as testing effectiveness, supplements must be examined for safety. Bitter orange has been associated with chest pain, anxiety, ventricular fibrillation, ischemic stroke, myocardial infarction (heart attack) and even death (National Institute of Health, 2015).

As with effectiveness and efficacy trials, it can be difficult to know whether bitter orange itself is causing these adverse effects or whether it is down to other ingredients combined with bitter orange in many supplements.

A 60-day double blind placebo-controlled study (Kaats, Miller, Preuss and Stohs, 2013) assessed the safety of bitter orange in 50 participants both alone and in combination with two other ingredients (naringin and hesperidin) when taken at a dosage of twice daily.

They examined blood pressure, heart rate, blood chemistry and blood cell counts, and found no adverse effects. Small differences in heart rate were found between participants who took bitter orange alone or in combination with the other ingredients, but these differences were not clinically significant.

In other words, they were not varied enough to indicate a medically relevant difference. This study concluded that at a dose of up to 98 mg per day for 60 days, bitter orange does not offer any cardiovascular health risks.

Overall, it appears that bitter orange may be a safe and effective way to produce a small amount of weight loss, but long-term studies are needed to really examine both its effectiveness and its safety.

2. Caffeine


Caffeine is a popular stimulant usually found in coffee and tea, but in supplements it is added either as an isolated substance or in the form of a variety of herbs (including guarana, kola, nut, or yerba mate).

It is proposed to help with weight loss by stimulating thermogenesis and fat oxidation. In other words, it produces heat in the body to use energy, and breaks down fat to use as energy.

Most studies on the effects of caffeine have been conducted using supplements containing multiple ingredients, so again, it is difficult to determine its effectiveness as a stand-alone ingredient.

In one 24-week study by Liu, Smith, Fujioka and Greenway (2013) participants were split into three groups. A third were given a combination supplement of 200 mg caffeine and 20 mg ephedrine, a third were given leptin A-200 (a hormone which controls hunger) and a final third were given a combination of both the supplement and leptin.

The researchers found that participants taking the supplement and those taking the combination of the supplement and leptin lost significant amounts of weight compared to those only taking leptin, and they also had a reduced whole body fat mass. Those in the combination group also showed significant reductions in visceral fat (the dangerous fat surrounding organs).

Although this study does not identify the role of caffeine alone as a weight-loss supplement, it does indicate that supplements containing caffeine can have the desired effect. Another study by McCarthy et al (2012) found that a supplement called OxyELITE Pro (which contains caffeine as one of six active ingredients) also showed a decrease in body weight, body fat percentage and appetite.

A long-term investigation into the association between caffeine and weight change was conducted by Lopez-Garcia et al (2006). Over 18000 men and women were followed up over a course of 12 years, during which time their caffeine intake and weight change was assessed (albeit caffeine intake was only assessed every 2-4 years, and weight change only between the beginning and the end of the study).

The study found that all participants gained weight on average, but that those who increased their caffeine consumption gained less weight than those who decreased their consumption. The long-term nature of this study is positive but it is unclear whether other confounding variables may have had a greater effect on weight change rather than simple caffeine consumption.

In spite of this positive evidence in favour of supplements containing caffeine, it is not possible to say whether caffeine itself has any benefits for weight loss because no studies have been conducted on it as a supplement in isolation. Furthermore, it has been associated with some severe health problems.

According to Yen and Ewald (2012) caffeine consumption can lead to sleep disturbances, jitteriness, nervousness, and when taken in high doses can cause nausea and vomiting, tachycardia (a rapid heart rate), seizures and cerebral edema (excess fluid in the brain).

These effects can also be exacerbated when caffeine is combined with other stimulants (including bitter orange and ephedrine). However, these effects are not usually found for dosages under 400 mg/day for a healthy adult (NIH, 2015).

3. Raspberry Ketones


Ketones are organic acidic compounds which have been claimed to help the body break down fat more efficiently. They are a very popular dietary supplement, but unfortunately the scientific evidence to back up their effectiveness is extremely limited.

In fact, only one study (Hofheins et al, 2012) has been conducted on the effect of ketones on human beings, and this study used ketones in combination with a multitude of other ingredients (caffeine, bitter orange, ginger root extract, garlic root extract, cayenne extract, L-theanine and pepper extract).

Over the course of eight weeks, 70 healthy men and women were randomly assigned to ingest either 4 capsules per day of METABO (the combination supplement) or a placebo.

All subjects then undertook a calorie restricted diet (500 calories fewer than RDA) and exercise regime (60 minutes, 30x a week) alongside 8 weeks of supplement consumption. Compared to the placebo group, participants taking METABO lost significantly more body weight (1.5kg more) and fat mass.

Although this study suggests that the METABO supplement does aid with weight loss when combined with a healthy diet and lifestyle, there is no evidence to suggest that the raspberry ketones had any influence upon the results.

Alongside limited evidence of ketone effectiveness in humans, there are also no studies which examine the safety of ketones. Speculation over the ability of ketones to lower blood sugar levels and decrease risk of bleeding are mentioned on the ‘Live Science‘ website, but this evidence is not backed up by scientific evidence.

Nevertheless, for those with diabetes it may be wise to be cautious, because both of the above effects can cause health problems. Furthermore, the website also suggests that ketones may cause changes in inflammatory processes, and lead to heart palpitations and shakiness. They may also interact with medicines and hormones in a negative manner. As with all supplements, these effects will only occur at high doses, but it is unclear what a safe dosage of ketones is.

4. Conjugated Linoleic Acid


Conjugated Linoleic Acid (CLA) is usually found in beef and dairy products, vegetable oil, seafood, and a variety of processed foods. Research has suggested that at high doses (more so than can be achieved through diet), CLA can have a positive influence on body composition by reducing body fat and increasing lean muscle mass.

For instance, in a study of 63 Chinese participants by Chen et al (2012), 30 participants were prescribed 1.7 grams CLA or a placebo twice a day for 12 weeks. Body composition was measured through BMI, body weight, body fat mass, visceral fat mass, subcutaneous fat mass, body fat percentage, waist-to-hip ratio and lean body mass.

After 12 weeks, the study found that participants who had taken CLA had significantly decreased body weight, BMI, total fat mass, body fat percentage, subcutaneous fat mass, and waist-to-hip ratio. There was no decrease in visceral fat mass, suggesting that changes in diet will also be necessary in order to maintain health (recall that visceral fat is potentially the most dangerous type of body fat).

The study failed to find any adverse side-effects, suggesting that CLA may be safe for use. It is worth noting that these effects were found after 1.7g of CLA was ingested twice a day. That is an awful lot of CLA, and so it may not be healthy to be ingesting such a large amount of a substance which is only found in the diet in small amounts.

Other research has also promoted the benefits of CLA for weight loss. Ormsbee et al (2013) investigated the effect of CLA alongside green tea, caffeine and branched chain amino acids when combined within a dietary supplement, and found that the supplement led to a significant decrease in total fat and fat surrounding the trunk and upper body (android fat).

Furthermore, satiety increased and desire to eat decreased. They did find however, that some participants reported side-effects of headache, anxiety and jitteriness. As with other supplements, the combination of ingredients cannot confirm that CLA is particularly beneficial, so these results should be interpreted with caution.

Despite the generally positive claims of these studies, there is conflicting evidence as to CLA’s effectiveness for improving weight loss. Onakpoya et al (2011) performed a systematic review of the evidence surrounding the long-term effectiveness of CLA for weight loss, and found that of the seven studies included, four had serious flaws in their methodology, and that there are a variety of adverse side effects including constipation and diarrhea.

Nevertheless, CLA did appear to show statistically significant improvements in weight loss, but these changes were small and their clinical significance is not clear. In other words, although CLA may improve weight loss, these improvements will be small and the side effects may not be worth the improvements. More research is required in order to solidify the apparent effectiveness of supplements containing CLA as a weight loss tool.

5. Green Tea


Green tea contains compounds known as catechins (in particular a catechin called EGCG) which are thought to be responsible for its apparent weight loss effect.

Green tea also contains caffeine which research has shown may lead to weight loss, but it is important to remember that caffeine is also associated with serious health problems when taken in excess.

Green tea is thought to promote weight loss by increasing energy expenditure and fat oxidation, and by reducing fat absorption and lipogenesis (the metabolic formation of fat).

Green tea is often found in combination with caffeine in dietary supplements, and it is thought that they may work together to provide a boost to weight loss. Studies described by the National Institutes of Health have shown that when catechins are combined with caffeine, they provide a significant increase in fat oxidation, which does not occur with caffeine alone.

Furthermore, the catechin EGCG alone does not increase fat oxidation or energy expenditure through metabolic rate. It appears that only when these two substances are combined that weight loss effects are found.

As a stand-alone supplement, a Cochrane review meta-analysis by Jurgens et al (2012) suggests that green-tea is ineffective for weight loss and maintenance. 18 studies were included, which led to a total of 1945 participants who took green tea or a placebo for 12 to 13 weeks in length.

It was found that although those who were given green tea did lose weight, the weight loss was very small and not statistically significant. Furthermore, weight maintenance was no better for green tea compared with placebos.

The Cochrane review also assessed negative effects of green tea, and found that most of the effects, including nausea, constipation and increased blood pressure were mild to moderate, but were not related to either the green tea or the placebo.

In light of this review, it seems that green tea alone will not cause harm to the dieter, but is also very unlikely to lead to weight loss.

Interactions Between Supplements and Exercise


Alongside adding supplements to your diet as a stand-alone weight-loss treatment, they can also be used in order to improve or enhance other aspects of a weight-loss regime. Recent research has begun to focus on the role of supplements in exercise performance.

Whey protein has been of particular interest to many researchers, and the emerging evidence suggests that this may be a worthwhile supplement to add to one’s diet, because it can help to increase muscle mass. This in turn can lead to a greater level of fat-burning whilst at rest.

Cermak et al (2012) performed a meta-analysis of 22 randomised control trials which assessed a total of 680 participants aged between 19 and 72 years of age.

Protein supplementation led to a highly significant positive effect on fat-free mass (similar to lean body mass) and strength. These effects remained when the resistance training was particularly prolonged, and were found for both younger and older participants.

There is also some evidence that protein supplements can reduce delayed onset muscle soreness (DOMS), which is the pain experienced the day after exercise. Haub et al (2014) compared the effectiveness of four different supplements on post-exercise muscle pain; whey protein, soy protein, wheat protein and water.

They found that compared to water, all three protein supplements led to a decrease in DOMS when consumed prior to exercise in men and women. There was no difference between the protein source, suggesting that a multitude of protein supplements may be effective at reducing DOMS.

This research suggests that even if dietary supplements aren’t particularly effective as a stand-alone tool for weight loss, they may help with other aspects of your weight-loss programme.

Indeed, despite the fact that only a small number of the hundreds of ingredients found in dietary supplements out there have been discussed in this guide, not one of them has evidence which conclusively proves that they are effective tools for weight loss.

The studies which do show that they are effective are often short and have small participant numbers. There are also a variety of possible adverse health effects associated with each ingredient, particularly at high doses as found in many supplements. Nevertheless, they do appear to have benefits for improving both the effectiveness of exercise, and post-exercise pain, which may act as a motivating agent in many cases.


When considering adding supplements to your diet, it is important to assess whether they have been examined scientifically in order to substantiate their claims.

It is also important to be aware of their side-effects, and what the safe dosages are. Most supplements found in health food shops, supermarkets and chemists are not regulated in the same way as medicines, and yet most people use them in order to improve their health.

Therefore, knowledge is necessary before one decides to incorporate them into their diet. In some cases, the health risks are not worth the benefits.

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