Weight-loss supplements promise big results, but are they backed by research – or just clever marketing? Photo / 123rf
We would all love to pop a pill and lose weight. But do the claims behind many of the natural ‘fat-busting’ supplements stand up?
The idea of simply being able to pop a daily tablet and watch the kilos magically melt away has been a long-held fantasy for anyone keen to shed some excess weight.
For decades, this has been exploited by the supplement industry which has generated billions in profits from selling products branded as aiding weight loss, even though the evidence for their benefit and safety is often distinctly dubious.
“There’s always been a lot of interest in anything that’ll help lose weight,” says Dr Pieter Cohen, an associate professor at Harvard Medical School and an expert when it comes to monitoring the safety of supplements. “Things that are quick and fast and don’t have any risk, that’s everyone’s dream. And the supplement industry has been selling products based on that hope and wish for years.”
Yet with the advent of Wegovy and Mounjaro, the highly successful class of weight-loss drugs that work by mimicking the actions of the GLP-1 gut hormone on appetite centres in the brain, it appeared as though the market for these supplements might have faded away.
Instead, according to Cohen, it has had the opposite impact. The hype associated with these drugs, combined with the high cost, limited availability, and general consumer reluctance for regular self-injections, has only intensified the desire for any kind of weight-loss powder or pill.
As a result, Cohen says growing numbers of wellness companies, often supported by unwitting social media influencers, are jumping on the bandwagon of GLP-1 drugs and exploiting the lax regulations of the supplement industry to claim their products offer similar benefits to these drugs, based on limited or negligible evidence.
“So many companies have gone back and said, ‘You know what, could we market or position our product as a natural version of GLP-1s?’” says Cohen. “They’ll take some lab experiment where the supplement might have expressed a little more GLP-1 in a petri dish compared with something else and then use that to suggest that it might have the same effect as these injectable medications, but without the cost or needing injections. And that’s absurd, but it’s completely permitted given the laws.”
So what are the latest so-called “fat-busting” supplements gaining traction online, what do they claim, and what do we really know?
The claims
A stimulant found in tea and coffee, caffeine is well known for its effects on boosting energy, but there is some research that suggests caffeine may help to stimulate brown adipose tissue, sometimes known as “brown fat”, which actually helps burn calories through generating body heat.
The reality
Just taking caffeine pills on their own will not be sufficient to burn significant amounts of fat, without significant lifestyle change and dietary adaptation. Cohen also points out the existing research has only shown very moderate weight loss benefits.
“It’s in the same boat as other supplements,” he says. “Maybe you’ll find a small dataset that shows it can lead to an ounce of weight loss in 20 mice. But are there clinical trials demonstrating prolonged weight loss and safety? No, that simply doesn’t exist.”
The risks
Many people experience side effects from caffeine supplements such as sleep problems, irritable mood, anxiety, muscle tremors, gastrointestinal problems and a rise in blood pressure. In high doses, caffeine can cause vomiting and seizures.
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Programmes such as WeightWatchers, which attempt to drive behavioural changes over time regarding eating behaviour and physical activity, are thought to be more effective.
The claims
Jumping on the fervour for weight-loss supplements, Kourtney Kardashian launched her own range last year, called Lemme. Its GLP-1 Daily supplement contains a mix of different plant extracts: eriomin lemon fruit extract, supresa saffron extract and morosil red orange fruit extract.
Promoted as a way of getting an “all-natural” GLP-1 boost, Lemme’s marketing leans heavily on a small handful of studies that suggest these individual extracts can reduce cravings, increase GLP-1 levels, and aid minor weight loss.
The reality
According to Gregory Lopez, research lead at Canada-based Examine, the leading source of data on supplements, the supposed evidence for the individual ingredients on GLP-1 levels is not as impressive as it may sound. He highlights a study cited by the company that describes how one of the extracts induced a GLP-1 response that was 17% higher than in a control group. “That may sound impressive until it’s put in context,” he says. “GLP-1 naturally fluctuates and can double or triple after a meal. [The diabetes drug] Ozempic is dosed to raise blood levels much more than that.”
The risks
Basically, we don’t know. Lopez says that all existing data on the plant extracts within Lemme only relate to when they’re consumed individually, and there is no evidence for how they might impact the body when taken in a combined cocktail. “Maybe they synergise positively, maybe negatively,” he says. “Who knows?”
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Lopez points out that exercise raises GLP-1 by a similar amount and is completely free.
The claims
Green tea contains plant chemicals known as EGCG, which have been linked to weight loss based on ideas that they increase energy expenditure and prompt the body to burn more fat for energy.
The reality
A few studies have indicated EGCG may help you burn more calories, even when you’re not doing any more physical activity. However, the evidence that this translates into significant weight loss still isn’t very strong.
“I think that EGCG may work to lose a little weight,” says Lopez. “The effect may also be higher in people with obesity. The problem is that moderate amounts of EGCG aren’t particularly effective. If it works, it probably starts working at doses of 300mg and above. At a very, very rough estimate, that’s around eight or more cups [per day].”
The risks
EGCG can either be ingested through drinking green tea itself or taking supplements, with the latter presenting an easier way of getting higher doses. However, Lopez also points out there’s some evidence to suggest high doses of EGCG can cause liver damage, or induce anxiety, insomnia, irritability and tremors.
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Nick Fuller, an associate professor at the University of Sydney, is an advocate of evidence-based lifestyle interventions such as intermittent-restricted eating, an approach that combines periods of weight loss and weight management.
The claims
A bitter-tasting and yellow-coloured plant chemical found in some berries and herbs, berberine has been used in Chinese and Ayurvedic medicine for centuries. A potent natural antibiotic that can be used to treat bacterial diarrhoea, pre-2023 berberine was best known as an alternative medicine which was sometimes prescribed by dietitians to help Type 2 diabetics with blood sugar control, with some studies suggesting it can reduce insulin resistance.
But then it went viral. In 2023, growing numbers of TikTokers began making content about berberine, calling it “Nature’s Ozempic”. Thousands of users started making claims that berberine could reduce food cravings, lower cholesterol and decrease belly fat. One supplement company reported sales soaring by more than 165% in just a few months.
The reality
According to Lopez, the evidence base for weight loss is somewhat sketchy. While a 2022 review of research trials published in the journal Frontiers of Nutrition reported that people who took berberine for at least two months lost weight, other studies have found nothing.
“There are quite a few studies looking at this, but the data’s pretty messy,” says Lopez. “My take is that if berberine works at all for weight loss, it only seems to help shed a couple of pounds at most.”
The risks
Lopez says anyone considering taking berberine should first speak to their doctor, particularly if taking existing medications, as it can interact with various drugs. “Berberine can also cause nausea or stool changes, but some people find these side effects minimal or tolerable,” he says. “Berberine should also be avoided when pregnant or breastfeeding as there’s some concerning evidence suggesting it could be a problem.”
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It’s probably more effective to focus on cutting your daily calorie intake.
The claims
A natural compound found in the exoskeleton of shellfish, chitosan is sometimes used to reduce bleeding from wounds. However, in recent years it has also been promoted as a potent “fat blocker”, capable of binding with the fat content in food and preventing it being absorbed by the body.
The reality
Like many natural supplements, research is mixed but one particularly well-orchestrated study found that chitosan users lost an average of about 2.7kg of weight, and Lopez is more convinced of its benefits compared with either Lemme or berberine.
“I’m a bit more confident it would work for weight loss,” he says. “It looks like, on average, people can expect to shed a few pounds over the course of months when taking doses on the higher side of 1500-4500mg per day. But I doubt it would lead to major weight loss for most people.”
The risks
Reported side effects from taking chitosan include flatulence, bloating, constipation, indigestion, nausea and heartburn.
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Losing significant amounts of body weight would likely require a course of GLP-1 drugs.
Lastly, Cohen points out that if you are taking a dietary supplement and losing weight, it could be dangerous. One of the consequences of the under-regulation of the supplement industry is that some products, particularly when purchased online, can contain potentially dangerous additives such as amphetamine and methamphetamine.
Research has shown that in the US, tens of thousands of people are hospitalised every year through consuming weight-loss supplements that turned out to contain these ingredients.
“The problem is that manufacturers can advertise their product as having weight-loss benefits, but they know they don’t have a legal ingredient that’s proven to lead to weight loss,” he says.
“I always advise my patients, if you’re losing weight with a supplement, then it’s very important to stop it, because you have no idea what’s actually in there, and people have run into liver damage, or unnecessary strain to their heart through consuming supplements which contain undeclared powerful pharmaceuticals. So these are the kinds of problems that can occur.”
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