Some swear by chewing 32 times to aid digestion; others stick to raw vegetables and fruit; many opt for high-protein diets in the form of fish, chicken and beef; a few proclaim the powers of grapefruit juice.
Whichever diet you follow, there is a good chance it has been challenged this week by a leading doctor exposing the "myths and fairytales" surrounding some of the world's best-known food fads.
Professor Chris Hawkey, president of the British Society of Gastroenterology (BSG), listed more than a dozen famous diets when he addressed Gastro 2009, a major conference for doctors recently.
They include "rawisim", the grapefruit diet and the alkaline diet.
The chewing movement emerged in the 19th century with the claim that chewing each mouthful 32 times helped digestion.
"Gladstone was apparently very eccentrically in favour of this diet," Prof Hawkey said of the British prime minister who died in 1898.
"The idea is that salivary enzymes start digestion."
However, like many other diets, it was based more on "theory than evidence", according to Prof Hawkey.
As for the Hollywood grapefruit diet, which is based on the belief the fruit contains an enzyme that breaks down fat and which Kylie Minogue is reported to have used, Prof Hawkey argues the chemical is unlikely to even make it through the gut and into the body, where it is meant to do its work.
"Food has been shrouded in myths and fairy tales since time immemorial," he said, arguing that some people become "quasi-religious" about what they eat.
"But what's important is to recognise that, despite the popularity of fad diets, we are losing a grip on the fight with obesity."
His comments come as a survey by the BSG shows one in five Londoners would turn to weight-loss pills to slim down.
As for the Atkins Nutritional Approach, the famous diet that is low in carbohydrates and high in protein, one in five women would try it, but only 2% believe it is healthy.
For Prof Hawkey, the diet is the one of the few that carries at least a small amount of evidence.
"It is not terribly healthy in the sense that you are going to have a lot of fat, but if you lose weight then it is a good thing," he said.
"The theory is that it resets the metabolic rate and there is some science to back that up."
He argues there is no harm in any diet that retains some nutritional balance and makes an individual lose weight.
Among the more balanced diets he mentions is one promoted by the nutritionist Esther Blum, who advocates eating full-fat foods in moderation to help metabolise cholesterol and to improve sex drive.
Its famous fans include Sarah Jessica Parker and Teri Hatcher.
"I'm all for informed scientists and practitioners actually debunking some of the mythology around diets," professor of medical psychology at Leeds University Andrew Hill said.
"People are looking for quick-fix repairs, but in fact they are very rare, particularly in relation to being overweight," Prof Hill said.
"The idea that some new discovery of a new way of combining food will give you an instant fix to your weight or health problem is nearly always misinformed.
"Health isn't immediately reparable; weight isn't immediately modifiable."
- Guardian News and Media.
Flawed favourites
Six diets that earn Prof Chris Hawkey's disapproval
The hallelujah diet: A low-calorie vegan based diet based on Genesis 1:29, while ignoring God's suggestion in Genesis 9:3 that a bit of meat might be a good idea too.
A Kellogg diet: A vegetarian diet, supplemented by an enema machine that delivered several gallons of water to cleanse the colon, followed by yoghurt to replace the intestinal flora of the bowel, which Dr John Kellogg (founder of the cereal empire) advocated for patients such as George Bernard Shaw, Johnny Weissmuller, Henry Ford and Sarah Bernhardt.
The Hollywood grapefruit diet: Followers believe grapefruit contains a fat-burning enzyme.
The apple or cider vinegar diet: A spoonful before food is said to counter alkalinity, in the belief that excess sugar causes yeast-based illnesses.
The tiger diet: Based on the idea that eating raw food is best, as humans did thousands of years ago.
Followed by Mel Gibson it involves raw meat, avocados and olive oil.
Fruitarian diets: Adopt a belief that fruit was the diet of mankind in the Garden of Eden - and interestingly, most include apples.
