Michele Verroken, director for Drug-Free Sport at UK Sport, replies: Anything that affects the body in the way that these tablets do should be approached with caution, particularly as there are often side-effects. These tablets are available over the counter and aren't governed by the guidelines that medicines have to go through. Fat burning products contain stimulants, sometimes nothing more harmless than caffeine, but some contain a substance called ephedra. Information from America suggests it can cause heart problems and even premature death. By relying on these tablets you may also be missing out on the benefits of a healthy diet and a good exercise plan.

Men's Fitness adds: The Food Standards Agency recently issued a health alert against fat-burner pills that contain DNP (also known as 2, 4-Dinitrophenol). Research suggests that these capsules are very dangerous to health. Taking three or four such capsules (1,000mg of DNP) in one go could result in death, while smaller amounts taken over longer periods are known to cause serious defects, such as cataracts. They therefore advise consumers to avoid any product containing the substance.