At the top of the diet scam list are pills that promise to boost your metabolism and help you burn calories or fat faster.
Consultant dietitian and spokesperson for the British Dietetic Association, Sian Porter, tells us: "Many of these claims are based on poor studies which haven't been rigorously tested. They can contain caffeine which affects your heart rate and can be dangerous."
The Medical and Healthcare products Regulatory Agency (MHRA) is the body which makes sure medicines sold and supplied in the UK are acceptably safe.
It says that thousands of women in the UK buy slimming pills from websites and are oblivious to the fact that many sites belong to unscrupulous vendors.
It says many of these sell counterfeit drugs that are harmful and in some cases can be life threatening; at the very least you could be ripped off - at worst they could kill.
Many of the diet pills have herbal ingredients with no proven research or evidence behind their claims.
There are even websites offering a diet product containing hCG (human chorionic gonadotrophin), which is found in the urine of pregnant women.
Sian Porter says some herbal products have appetite suppressants which can mess you up and lead to dependency issues.
Tam Fry from the National Obesity Forum says: "I wouldn't touch anything from these websites with a bargepole. The web is alive with unregulated, unreputable scams which have no scientific backing but make outrageous claims."
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