Adopting a detox diet - often popular in January - is a waste of time and money, a leading scientist has said.
Detox diets usually advise eating a lot of fruit
Dr Andrew Wadge, of the Food Standards Agency (FSA), said regimes purporting to cleanse the body were "nonsense".
The detox market - which can include diets, tablets and drinks said to flush out toxins - is thought to be worth tens of millions of pounds.
In his blog, Dr Wadge said water and exercise were enough to help the body rid itself of harmful chemicals.
The chief scientist of the government's food watchdog wrote: "There's a lot of nonsense talked about 'detoxing' and most people seem to forget that we are born with a built-in detox mechanism.
"It's called the liver. So my advice would be to ditch the detox diets and supplements and buy yourself something nice with the money you've saved."
Detox-based diets, which are sometimes endorsed by celebrities, can include the use of tablets, socks, body wraps, diets, eating nettle root extract or drinking herbal infusions or "oxygenated" water in a bid to make natural procedures more effective.
Some products claim to enhance the immune system, relieve pain, flush out toxins and stimulate circulation.
But, urging people to save time and money, Dr Wadge advised: "First, drink a glass or two of water (tap is fine, cheaper and more sustainable than bottled); second, get a little exercise - maybe a walk in the park - and third, enjoy some nice home-cooked food."
The gut prevents bacteria and many toxins from entering the body, he said, while the liver contributes to breaking down harmful chemicals which are then excreted by the kidneys.
Last year scientists from the Sense About Science organisation said detox was a waste of time, arguing that water, fresh air and sleep is all that is needed.
But, following those comments, high street chemist Boots, which has sold detox products, maintained that they have a role to play when combined with a healthy diet and exercise.