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Do weight loss pills help you lose weight?

We take a closer look at the active ingredients of various diet pills and find the evidence is sketchy.

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Last updated: 07 May 2021


Checked for accuracy by our qualified fact-checkers and verifiers. Find out more about fact-checking at CHOICE.

According to the latest research from the Australian Bureau of Statistics (ABS), a staggering 67% of Australians are now overweight or obese. 

With alarming stats such as this, it's no wonder so many of us are turning to over-the-counter help in the form of weight-loss pills.

The pills that claim to make you slim and trim are an integral part of Australia's billion-dollar weight-loss industry. 

So we took a closer look at a selection of diet pills and checked out the ingredients that reportedly give these products their fat-busting properties.

People who are considering using weight-loss supplements should talk with their doctor to discuss these products' potential benefits and risks, especially if they have an underlying health condition.

Claims vs reality

You've seen the ads – you know, the ones that say "I lost eight kilograms with this product!" or "Yes, I want my body to absorb less fat!" 

They can be pretty convincing, especially when supported by "scientific evidence" and amazing "testimonials", complete with before and after shots.

Such dramatic testimonials used to come with the fine print that these people are "exceptional" and that "individual results may vary". But in 2005, the law changed so that testimonials and photos must be of typical cases. 

Yet on the testimonial pages of some websites, many cases still seem exceptional. If you look at the fine print, it's often explained that their results are due to a lot more than taking product X, such as changes in diet and levels of physical activity.

Do weight-loss pills work?

You'll typically find that weight-loss pills are designed to be used in conjunction with an energy-controlled diet and regular exercise. But isn't that what we're trying to avoid by taking the pills in the first place? 

So we took a closer look at the literature around the most common active ingredients. Several systematic reviews have concluded that, at best, more research is needed before any conclusions can be drawn. 

Multiple ingredients

Complicating the interpretation of many studies is that most weight-loss supplements contain multiple ingredients. This makes it difficult to isolate the effects of each ingredient or how they interact with each other.

Overall, the current evidence for the effectiveness and safety of these products is pretty sketchy. 

The truth is that these products may or may not assist with weight loss. But whatever their impact, it seems that we can't escape actually doing the hard yards, such as changing our diets or getting more exercise, if we want to see results.

 Analysing the active ingredients

Weight-loss pills tend to contain a mix of herbs and vitamins, and often stimulants such as caffeine, which can result in high blood pressure and heart palpitations. 

Herbs contain many chemicals, the presence and concentration of which can vary according to the source and the preparation. And in most of these weight-loss pills, ingredients are only individually tested for safety, despite the fact that they may interact with one another or with other medications in ways that may be less safe.

Here we look at some of the most common ingredients in weight-loss pills, what they claim to do, and whether there's any evidence they're effective. 

Government approved? Don't bet on it

If you think weight-loss pills are evaluated for safety and efficacy the way prescription medicines are, think again.

The Therapeutic Goods Administration (TGA) is the body that's been charged with regulating complementary medicines. In Australia, all complementary and alternative medicines – such as weight-loss pills – need to be entered on the Australian Register of Therapeutic Goods

Manufacturers have to hold a file of evidence to prove that their products work. However, based on the literature we looked at, we suspect their "proof" is pretty underwhelming

On this register, there are two types of products: "registered goods" and "listed goods". It's important to know the difference.

Registered goods 

These are medicines (identified by an AUST R number) that are considered high risk. They're evaluated by the TGA for quality, safety and efficacy before being released onto the market.

Listed goods

These are medicines (identified by an AUST L number) that are considered lower risk. They must only contain ingredients that have had their safety and quality approved for use in listed products, but they aren't evaluated for efficacy.

In 2008, there were about 100 times more listed weight-loss products than registered products – today there are probably even more.

Manufacturers can apply for a listing by just filling in an online form and paying a fee. About one in five (20%) products are randomly audited to make sure they meet standards. Manufacturers also have to hold a file of evidence to prove that their products work. However, based on the literature we looked at, we suspect their "proof" is pretty underwhelming. 

the latin seed weight loss pills

Latin Seed was recalled after tests revealed it contained poisonous yellow oleander seeds.

Recalled slimming products

There have been product recalls in the past in Australia that bring into question the regulation around listed weight-loss aids. 

Weight-loss chocolate

A few years ago, weight-loss chocolate bars were pulled from sale as they contained an unlisted ingredient – the prescription drug sibutramine. Once a leading prescription weight-loss medicine, sibutramine was withdrawn from the Australian market after being associated with cardiac events such as non-fatal heart attack and stroke.

Latin Seed

In another worrying event, the heavily advertised Latin Seed was withdrawn for containing poisonous yellow oleander instead of candle nut, as the label claimed. Yellow oleander can cause a variety of symptoms from diarrhoea to heart damage.

These events may be unusual, but the fact that they do happen makes it difficult to see how the TGA can consider these products "low risk".

The dangers of buying diet pills online

Weight-loss supplements containing sibutramine and Latin Seed are readily available online. We noticed that many of these online products don't always state the actual concentrations of their ingredients in their online listings, which could make taking them risky. 

The listed content of ingredients in supplements can also be inaccurate. One 2015 US study found the actual content of a number of botanical supplements varied widely from what was listed on the label. For example, yohimbine was found to vary from between 23% and 147% from what the label said the products contained. 

The TGA recommends that consumers exercise extreme caution when buying any medicines or supplements from overseas online retailers, as they're not regulated by the TGA and may contain harmful, dangerous or banned ingredients.

We care about accuracy. See something that's not quite right in this article? Let us know or read more about fact-checking at CHOICE.

Stock images: Getty, unless otherwise stated.