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.
What is it?
It's a derivative of citric acid, usually extracted from the fruit rind of the plant Garcinia cambogia. It may also be listed as brindleberry, Malabar tamarind, or Garcinia gummi-gutta.
What they say it does
Modifies metabolism, reduces fat synthesis and decreases appetite.
Can they prove it?
Studies provide contradictory evidence. Some show positive results, while others show no difference between the group taking HCA and the placebo. More comprehensive studies are needed.
Side effects and interactions
Some studies have shown it can cause headache, nausea, and symptoms in the upper respiratory tract, stomach and intestines, and liver damage. The safety of HCA during pregnancy and breastfeeding has not been established, so it should be avoided at these times.
Products it's been found in
It's been found as a standalone supplement and in weight-loss blends such as Naturopathica FatBlaster Max.
What is it?
An extract of the Seville orange, it's also known as Citrus aurantium. It's used in place of ephedra, as it contains similar compounds.
What they say it does
Increases metabolism and fat burning while decreasing appetite.
Can they prove it?
Promising evidence is limited. More research is needed on its safety and effectiveness.
Side effects and interactions
Bitter orange has been linked with fainting, heart attack and stroke, so people who have heart conditions or are taking other medications are advised to avoid it. Because the safety and effects of products containing bitter orange during pregnancy and breast feeding are unknown, pregnant women and nursing mothers should avoid them too.
Products it's been found in
It's been found as a standalone supplement and in products such as Body Effects by Power Performance Products, FatBlaster and FatBlaster Max.
What is it?
It's capsaicin from chillies.
What they say it does
Increases metabolic rate and reduces appetite.
Can they prove it?
Studies on capsaicin are interesting, but mixed – one shows that having a spicy entrée can reduce your total food intake over the whole meal.
Side effects and interactions
Short-term burning pain, stomach irritation and upset, sweating, flushing, and runny nose have all been reported. In large long-term doses, more serious side effects such as liver or kidney damage could occur, as well as severe spikes in blood pressure. Capsaicin annuum may also have moderate interactions with some medications.
Products it's been found in
It's been found as a standalone supplement and in Hyroxycut Hardcore and Hyper-Shred.
What is it?
It's an extract of raw coffee beans – chlorogenic acid is believed to be the active ingredient.
What they say it does
Increases metabolism and glucose control, and helps with obesity, diabetes, high blood pressure, and Alzheimer's disease.
Can they prove it?
There are some positive results from studies, but the quality of the studies is poor. Plus there's insufficient evidence to suggest green coffee extract is effective, so more rigorous trials are needed.
Side effects and interactions
There are none known, but the product's safety hasn't been confirmed in a large analysis. It has the potential to increase heart rate and blood pressure, and to cause headaches. Green coffee contains caffeine, so it may cause similar side effects as regular coffee or caffeine consumption. For that reason, it isn't recommended for people with anxiety, bleeding disorders, irritable bowel syndrome, high cholesterol or high blood pressure – it may make all these conditions worse. It may also interact with certain medications. There's not enough reliable information about the safety of taking green coffee if you're pregnant or breastfeeding, so it's better to avoid it at these times.
Products it's been found in
It's been found as a standalone supplement and in EHP Labs Oxyshred, Optiburn Amped, Hydroxycut Hardcore Elite, and FatBlaster Max.
What is it?
It's the catechins extracted from green tea, Camellia sinensis.
What they say it does
Reduces fat synthesis and absorption, and increases metabolism.
Can they prove it?
The results have been conflicting. Some studies suggest it needs to be taken with caffeine to be effective. It might have a modest effect on body weight, but it hasn't been shown to produce or help maintain meaningful weight loss.
Side effects and interactions?
Deemed safe when formulated and taken appropriately, green tea and green tea extracts contain caffeine and so may cause side effects. There's some concern that green tea extracts may cause liver toxicity, especially if taken on an empty stomach. Other reported adverse effects include constipation, abdominal discomfort, nausea and increased blood pressure.
Products it's been found in
It's been found as a standalone supplement and in FatBlaster, FatBlaster Max, Body Effects from Power Performance supplements, and Hyper Shred.
What is it?
Also known as poliglusam, chitosan is found naturally in the cell walls of fungi, soil and sediments.But it's usually derived from the powdered shells of crustaceans.
What they say it does
Binds to dietary fat in the digestive tract to stop absorption.
Can they prove it?
Clinical studies have been small and mostly of low quality. They show varying results and only minor weight loss, which is probably clinically insignificant.
Side effects and interactions
If it does work, you could experience malabsorption of nutrients and loose, oily stools. Other reported side effects include flatulence, bloating, constipation, indigestion, nausea and heartburn.
Products it's been found in
It's been found as a standalone supplement and in FatBlaster FatMagnet .
What is it?
Chromium is an essential trace element commonly used in the form of chromium picolinate. It's commonly found in small amounts in meat, wholegrains, fruits and vegetables.
What they say it does
Enhances insulin sensitivity and fat burning. It may also increase lean body mass and reduce food intake, hunger levels and fat cravings.
Can they prove it?
Experts agree that there's insufficient evidence to recommend it as a weight-loss aid.
Side effects and interactions
Few serious adverse effects have been found, but some medications may interact with it. Chromium may also cause headache, watery stools, constipation, weakness, vertigo, nausea, vomiting and urticaria (hives).
Products it's been found in
It's been found as a standalone supplement and in RSP QuadraLean, Hydroxycut Hardcore, FatBlaster, FatBlaster Max, and Xenadrine Ultra.
What is it?
Carnitine is composed of the amino acids lysine and methionine. You may see it listed as L-carnitine or acetyl-L-carnitine. It's naturally present in foods such as meat, fish, milk and dairy products, and in small amounts in some plant foods.
What they say it does
L-carnitine is potentially beneficial for a range of health conditions such as obesity, diabetes, and heart disease. It may also aid weight loss and exercise recovery.
Can they prove it?
There have been several clinical trials with weight loss as a secondary outcome. They have indicated that carnitine may have a modest effect on body weight, although more research on its weight-loss credentials is needed.
Side effects and interactions
Nausea, vomiting, diarrhoea, abdominal cramps, and a "fishy" body odour have all been reported. L-carnitine may also increase the risk of cardiovascular disease.
Products it's been found in
It's been found as a standalone supplement and in RSP QuadraLean, Hydroxycut shred, Optiburn Amped, and FatBlaster Keto-Fit.
What is it?
Conjugated linoleic acid (also listed as CLA) is naturally occurring polyunsaturated fatty acid present in ruminant dairy products and meat. Commercial CLA is often produced from sunflower oil.
What they say it does
Promotes weight loss through the increased fat breakdown in the body. It's also claimed to help maintain weight loss, retain lean muscle mass, and control diabetes.
Can they prove it?
So far, studies suggest there's minimal effect on body weight and body fat, and some smaller studies show contradictory results. More studies are needed.
Side effects and interactions
Minor side effects have been reported, such as indigestion, abdominal discomfort and pain, constipation, diarrhoea, and loose stools.
Products it's been found in
It's been found as a standalone supplement and in BCAA Lean Energy, Optiburn Amped, and Oxyshred RSP QuadraLean.
What is it?
Yohimbe is derived from the bark of a West African evergreen tree (Pausinystalia yohimbe, Pausinystalia johimbe). It may also be listed as johimbe or yohimbine.
What they say it does
The extract is found in some dietary supplements that are promoted for weight loss, bodybuilding and libido enhancement in men.
Can they prove it?
Very little research has been done on the use of yohimbe for weight loss or its effect on body mass, and studies are often contradictory. There's very little conclusive evidence that it has an effect on either.
Side effects and interactions
Yohimbe can be dangerous. It can increase blood pressure and cause headaches, hypertension, anxiety, agitation, tachycardia, myocardial infarction (heart attack), cardiac failure, and even death, depending on the dosage. It's recommended that yohimbe should only be used under medical supervision because of its potential to produce serious adverse effects. Yohimbe extracts have been banned in many countries and the substance is considered to be a prescription-only medicine in Australia and is prohibited from being imported.
Products it's been found in
It's been found as a standalone supplement and in Hydroxycut Hardcore and EVLution Nutrition Trans4orm Thermogenic Energizing Fat Burner Supplement.
What is it?
Glucomannan is a soluble dietary fibre derived from konjac root (Amorphophallus konjac) that can absorb up to 50 times its weight in water. It's also known as conjac, konnyaku and konjonac..
What they say it does
Glucomannan is touted as an appetite suppressant that works by increasing feelings of satiety and fullness. It may also reduce fat and protein absorption in the gut.
Can they prove it?
Studies show it seems to have some beneficial health effects, such as lowering cholesterol, but there's little to no proof it helps with weight loss.
Side effects and interactions
Significant safety concerns have been reported for tablet forms of glucomannan because they could cause oesophageal obstructions as they swell with water. The tablets have been banned in Australia but the capsules and powdered forms are still available. The supplement may also cause loose stools, flatulence, diarrhoea, constipation, and abdominal discomfort.
Products it's been found in
It's found as a standalone supplement and in Natural Factors SlimStyles PGX Granules Unflavored and FitMiss Burn Women's 6 Stage Fat Burning System.
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.
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.
Stock images: Getty, unless otherwise stated.
