Weight loss pills: Do they work?

Can weight-loss supplements really back up their claims? Or is it just a lot of hot air?

weight loss supplements with measuring tape

Losing that cheerful Christmas bulge can be tricky. Exercise is hard, dieting is harder. But if you’re thinking of shelling out $20-plus for weight management supplements in the hope of a quick fix, don’t be hasty. They could be doing more harm than good.

Weight management supplements promise much, from helping to “manage those annoying wobbly bits”, to supporting “appetite control” and protecting “against comfort eating”.

While the fine print on the packs recommends the supplements should be used in conjunction with a healthy diet and regular exercise, you’d be forgiven for thinking you were getting a magic pill to solve your curvy problems.

We investigated some of the common ingredients in over-the-counter supplements to see if they’re effective – or even safe.

Green tea extract

Green tea extract (Camellia sinensis) has catechins and caffeine in it and, according to the companies selling it, may help increase energy levels, support a healthy metabolic rate, decrease waist size and assist weight loss.

But a 2016 report on liver damage caused by herbal and dietary supplements, commissioned by the United States’ National Institutes of Health (NIH), found green tea extract was linked to serious liver damage.

The study identified more than 50 cases since 2006 of liver injury attributed to the use of green tea extract supplements. The NIH’s measured advice to consumers: taking green tea extract might not be safe.

What about weight loss claims? The bottle of Ethical Nutrients’ Weight Loss Support states green tea may “assist weight loss” and “reduce body weight”.

However, a 2012 Cochrane Review of research on green tea extract concluded there was no statistically significant weight loss from taking the supplements.

Bitter orange

Bitter orange (Citrus aurantium), which contains the stimulant oxedrine (also known as synephrine), is supposed to burn calories and decrease appetite.

There have been cases of healthy people experiencing fainting, heart attack and stroke after taking bitter orange alone or with caffeine, although information about the dose and other ingredients in the pills wasn’t routinely collected, making a direct cause-effect relationship difficult to establish.

A 2015 review by Food Standards Australia New Zealand concluded there was no cause for concern based on the highest level of oxedrine it found in foods promoted for weight loss (39mg per day).

It “might slightly increase the number of calories you burn … but whether it can help you lose weight is unknown”.

However, other scientific reviews have arrived at different conclusions. A 2014 review by France’s food agency concluded there was insufficient data to set a safe dose but recommended oxedrine in supplements should be limited to 20mg per day.

A 2017 review by The Netherland’s National Institute for Public Health and the Environment also concluded there was insufficient data on oxedrine’s safety to determine a safe level.

Back here, products that deliver more than 30mg a day are prescription medicines. Other products can be sold as supplements. Healtheries Naturally Slim Fat Burner Thermogenic Capsules have 10mg of oxedrine per capsule, along with 17.5mg of caffeine. The label says you can take up to three capsules a day.

So does oxedrine help with weight loss? According to research reviewed by the US’s National Institutes of Health Office of Dietary Supplements, it “might slightly increase the number of calories you burn … but whether it can help you lose weight is unknown”.


Chromium’s an essential trace element and we need about 25 to 35mcg every day.

Chromium comes in two main forms, trivalent and hexavalent. The latter, also known as chromium-6, is the chromium that Erin Brockovich famously found in a California water supply and is linked to cancer. The type that our body needs is trivalent and in supplement form is called chromium picolinate.

It’s common for weight management supplements to chuck in some chromium picolinate for good measure – it’s supposed to decrease your appetite – but usually in small amounts.

There are chromium supplements that claim to help balance your blood sugar levels and manage cravings. Go Healthy’s Go Chromium has 3340mcg of chromium picolinate, which is the equivalent of 400mcg chromium. That’s more than 10 times what you need in your diet.

High doses can put you at risk of side effects such as watery stools, headaches, weakness, nausea, vomiting and hives.

As for the weight loss claims, a 2013 Cochrane Review concluded there wasn’t enough good evidence to show chromium picolinate supplements had any impact on weight loss.

Garcinia cambogia

Garcinia cambogia, billed as an exotic fruit extract, is a common weight management supplement on shop shelves. According to the packs, its active ingredient (hydroxycitric acid – HCA) suppresses appetite and encourages your body to use fat as an energy source, rather than storing it.

Good Health’s Garcinia Cambogia 9000 Plus, which has 9000mg of the stuff, claims to support healthy serotonin levels in the brain, helping you feel good and be less likely to succumb to cravings.

But there’s no conclusive evidence to support the fat-busting claims made for the extract. The long-term safety of the substance is also unknown.

Conjugated linoleic acid (CLA)

CLA is a fat mainly found in meat and dairy products and is claimed to reduce your body fat. According to Radiance’s TummyTone CLA, it helps “maintain a leaner body shape by modulating how cells store fat, especially around the abdomen, hips and thighs”.

A 2011 review published in the Journal of Obesity concluded CLA had shown “some potential benefit” for weight loss but more research was needed before any definitive conclusions could be drawn. According to the NIH, the supplement “seems to be safe” at up to 6g a day for up to a year, but can cause an upset stomach, constipation, diarrhoea and indigestion.


It’s common to see caffeine in weight management supplements. Ingredients such as guarana and green tea extract also contain caffeine, although their caffeine content may not be stated on the label.

You can find caffeine tablets that promise to “mobilise fat for use as fuel” and claim caffeine will increase metabolism and suppress appetite.

Caffeine’s effects can be increased when combined with other stimulants. According to the NIH, it’s safe up to about 500mg a day (equivalent to about six cups of coffee). But, as anyone who’s had that much coffee in a day knows, it can leave you nervous and shaky. At high doses it can cause nausea, vomiting, rapid heartbeat and seizures.

Can they really say that?

There is little regulation of dietary supplements and even less enforcement of the rules. Companies selling supplements can’t claim they:

  • treat or prevent a disease
  • alter the shape, structure, size or weight of the human body
  • prevent or interfere with the normal operation of a physiological function, whether permanently or temporarily, including increasing or accelerating that function.

According to Medsafe, this includes claiming a product:

  • burns fat
  • increases metabolism
  • suppresses appetite
  • increases thermogenesis
  • increases energy levels.

To cover themselves, supplement manufacturers frequently use words such as “may” or “could” or “helps support” as caveats. They also market their supplements as part of a weight management plan that includes exercise and a healthy diet.

Plans to overhaul supplement regulations and clamp down on health claims have been in the pipeline for more than a decade but are on hold. However, manufacturers can be prosecuted under the Fair Trading Act for making misleading statements or unsubstantiated claims.

We say

  • Better regulation of supplements is needed to ensure health claims are backed by good evidence of a product’s safety and efficacy.
  • If you’re spending money on supplements, don’t rely on the label claims. If you’re worried about your health, get advice from a qualified medical practitioner.


Calocurb, a New Zealand-made weight management supplement, was launched here and in the United States with much fanfare early last year. But is it safe?

Calocurb has been pitched as a world-first supplement. Taken before meals, it claims to make you feel fuller quicker and therefore reduces the amount of food you eat.

At $60 for a monthly subscription, it’s “Goodbye craving. Hello you”.

Its development was paid for in part by taxpayers. Government-owned Plant and Food Research spent $20 million over six years researching natural extracts that would act as an appetite suppressant and found a hops extract that did the trick.

However, the supplement triggered a life-threatening allergic reaction in a person in May 2018. The reaction started with abdominal discomfort and red, itchy hands after the person’s third dose. Symptoms got worse, to the point of losing consciousness, and after being hospitalised the patient was diagnosed with anaphylaxis.

Medsafe said an investigation was in process. In its public advice after the adverse reaction, the regulator pointed out it doesn’t evaluate dietary supplements for safety, efficacy and quality.

Calocurb users have left mixed reviews on the company’s Facebook page. Some are positive and others detail bloating, reflux, diarrhoea and, in some cases, no impact on eating habits or weight loss. The reviews were taken down by Calocurb in June, with the company telling reviewers it needed to comply with dietary supplement regulations. The regulations state a company advertising supplements can’t claim they’ve had a beneficial effect on the health of a person (see “Can they really say that?”).

The product was tested before it went to market but the results have yet to be published.

The supplement was tested by Plant and Food on 19 healthy, lean men during a two-week period. It showed the men ate about 225 fewer calories (the equivalent of about a large avocado) over 3.5 hours than those who were given a placebo.

Clinical research has still not been peer-reviewed or published, and the pills safety and efficacy can’t be quantified without long-term studies.

On the basis of those results, it was licensed by Plant and Food to supplement company Lifestream and the sales pitch began.

Plant and Food conducted a second clinical trial on 30 overweight and obese women last year, but the results have not been released.

Dr Andrew Dickson, a health sociologist at Massey University, is a critic of the supplement. He said the clinical research has still not been peer-reviewed or published, and the pills' safety and efficacy can’t be quantified without long-term studies.

Plant and Food wouldn’t show us the full research but said a safety review it commissioned prior to the clinical trials found hops extracts are “well tolerated”. The organisation confirmed it receives royalties from sales of Calocurb (it wouldn’t tell us how much). Its annual report states Calocurb was bought by 6000 people in the first three months and more than half of those people bought it again (it’s sold on a monthly subscription). Global sales of the supplement are expected to reach $20 million in the next three years.

A Lifestream spokesperson said up to five percent of customers surveyed have experienced side effects, the most common being a laxative effect, but that usually resolves after 48 hours and advice is given at purchase about how to minimise this. The company said allergic reactions are unpredictable: “everyone’s metabolism is different, so if a consumer does not like the product for any reason, we offer a money back guarantee.”

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