UK dieticians have come out strongly against detox diets, championed by some celebrities, saying they are a waste of time and money.
The theory behind detox - that dangerous toxins build up in the body - has been dismissed by the health experts as pseudo-scientific. They have pointed out that the body is anyway constantly cleaning itself.
There is no "potion or lotion" which could "magically" rid the body of chemicals, the British Dietetic Association (BDA) has warned.
Thousands of slimmers are expected to try a detox diet in the next few weeks, spurred by guilt over heavy drinking and eating during the festive period.
A wide range of different kits, including ready-prepared vitamin drinks and diet plans, are available on the high street and from specialist health shops.
Dieters undergoing a detox are usually advised to cut out a wide range of "unhealthy" foods and supplement their diet with vitamin drinks. They are told that chemicals and other pollutants remain in our bodies over time, causing health problems, and need to be removed.
But Dr Frankie Phillips, a spokesperson for the BDA, said: "The whole idea of detox is nonsense.
"The body is a well-developed system that has its own built-in mechanisms to detoxify and remove waste from top to toe.
"Skin, the gut and liver and kidneys are all chemically-controlled powerhouses that respond to signals in the form of, for example, hormones, to remove waste products - typically detoxifying the body constantly.
"There are no pills or specific drinks, patches or lotions that can do a magic job.
"If you have over-indulged on alcohol, for example, the liver works hard to break down the alcohol into products it can remove.
"Being well-hydrated is a sensible strategy.
"It sounds predicable, but for the vast majority of people, a sensible diet and regular physical activity really are the only ways to properly protect your health for the year ahead."
The BDA warns that only eating sensibly and drinking plenty of fluids can help the bodies' natural cleansing system.
The group recommends that New Year's diet resolutions include drinking enough fluids, around six to eight glasses a day is sufficient; keeping a diet diary; making small changes that will last, such as eating one extra portion of fruit or vegetables a day; and planning meals ahead.
The BDA represents registered dietitians across Britain and two-thirds of its members are employed by the NHS.