A quick Google search for weight-loss supplements brings up 165,000 results, but how many of these supplements have been proven to help you lose weight?
It’s estimated that over one-third of adults in the US have tried a diet supplement at some point and one in ten have tried a weight-loss supplement in the past year¹.
But do any of these weight-loss supplements actually work? Let’s take a look at the evidence.
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Probiotics have become very popular in the past few years as the importance of the integrity of the gut microbiome for good health has become clearer.
A meta-analysis of weight-loss studies comparing the use of probiotics with a placebo showed that probiotic use leads to a significant, albeit small, reduction in body weight and body-fat percentage compared to placebo².
Fiber has been shown to promote weight loss through various mechanisms. It increases satiety (feeling of fullness), decreases absorption of macronutrients, alters the secretion of gut hormones, and optimizes the gut microbiome³.
You should aim to get fiber from your diet through food sources such as vegetables, fruits, and whole grains, but the addition of fiber supplements to help reach those daily requirements has been shown to aid weight loss⁴.
There is a link between vitamin D deficiency and obesity. Obese people have lower vitamin D levels than non-obese people.
Two reasons have been proposed for this:
Adipose (fat) tissue stores vitamin D, resulting in lower plasma levels
Obese people may spend less time outdoors exercising in the sunshine
But the link appears to work the opposite way as well. Some studies have shown that vitamin D supplementation can aid weight loss in adults and children. The effect was most noticeable in a study looking at postmenopausal women, which combined vitamin D and calcium supplementation⁵ ⁶.
Green tea contains catechins and caffeine, both of which have been touted as weight-loss aids because of their stimulatory effect. The theory is that stimulants increase metabolic rate.
A meta-analysis of studies looking at the use of green tea or green tea extracts for weight loss found green tea preparations to exert a small weight-loss effect in overweight subjects. Because the effect was so small, the authors of the study doubted whether the results held much clinical significance. Importantly, the use of green tea was associated with some adverse effects, so it should only be used in moderation and under the guidance of your doctor⁷.
Vitamin C levels have been shown to be inversely related to body mass.
Studies show that people with adequate vitamin C levels burn 30% more fat during exercise than people with vitamin C deficiency. People with low vitamin C levels are more resistant to fat loss when exercising.
Supplementing your vitamin C level if it’s low, or making sure that your vitamin C levels are normal, may optimize the amount of weight you lose while exercising⁸.
Although fish oil supplementation has not been shown to aid weight loss generally, it has been found to decrease abdominal fat.
A large meta-analysis of studies of fish oil as a weight-loss supplement suggested that overweight or obese people may benefit from reducing abdominal fat with fish oil supplementation when combined with lifestyle modification⁹.
Adequate B-group vitamin levels (B1, B2, B3, B5, B6, B7, B9, B12) are necessary for optimal metabolism of fat, carbohydrates, and protein. B vitamins help the body obtain energy from food and support a healthy metabolism.
However, excess B vitamin levels may lead to weight gain¹⁰, so make sure that you stick to recommended daily allowances if you do decide to supplement with B-group vitamins.
Caffeine is a stimulant and a popular ingredient in many weight-loss supplements.
A large meta-analysis of studies looking at the effect of caffeine on weight loss concluded that caffeine may promote a reduction in weight, body mass index, and body fat¹¹.
There are so many weight-loss supplements available that it’s almost impossible to evaluate all of them.
The following weight-loss supplements have been shown to have no or very little effect on body weight¹²:
There are many potential problems with taking weight-loss supplements.
Some of the supplements advertised have not been extensively studied, so we may not be aware of all of the possible side effects and drug interactions. It’s important to remember that just because something is marketed as “natural”, it does not mean that it is safe or has no side effects.
The National Institutes of Health (NIH) has published the following list of things to remember when buying supplements¹³:
If you buy supplements online or from a store, they may not be the same as those tested in research studies.
If you are taking medication, have particular health issues, or are preparing for surgery, dietary supplements could adversely interact with what you have been prescribed.
Many supplements have not been tested on children, breastfeeding mothers, or pregnant women.
The listed ingredients on a supplement’s label may differ from its contents. For example, some products sold as bodybuilding, weight-loss, or sexual-enhancement supplements contain prescription drugs banned from dietary supplements or other unlisted ingredients which may be unsafe.
The regulations around the manufacture and distribution of dietary supplements are not as stringent as the rules for prescription or over-the-counter medication.
For these reasons, always talk to your doctor before starting any supplement.
Before reaching for supplements, it may be worth seeing a dietician or nutritionist to ensure that you are following the healthiest diet for you.
There are, however, some supplements that can aid you on your weight-loss journey. The two with the most evidence supporting their use are caffeine and fiber. Making sure that you have the recommended daily allowance of all of your vitamins and minerals also helps to support a healthy metabolism.
Be aware that supplements can be poorly regulated and may be harmful, so always speak to your doctor before starting any weight-loss supplements.
Dietary supplements for weight loss I Office of Dietary Supplements, NIH
Dietary and herbal supplements I National Center for Complementary and Integrative Health, NIH