Oxbridge scientists say they have unlocked the secret to a successful New Year diet.

Researchers believe no diet is perfect for everyone, and the key to picking the right one depends on hormones, genes and psychology.

Each plays a key role in our relationship with food - and why some of us tend to eat too much.

Scientists identified three broad groups: "feasters" who keep on eating because they never feel full; "constant cravers" who can't stop thinking about food; and "emotional eaters" who raid the biscuit tin in times of trouble.

According to the team, which included Government nutrition advisor Professor Susan Jebb, from Oxford University, and Cambridge geneticist Dr Giles Yeo, each group responds differently to different diets.

They tested their theories on 75 volunteers - 25 from each group - over three months last summer.

Dr Chris van Tulleken said feasters don't release enough of a hormone known as GLP1, which tells your brain you are full.

"If you are someone who goes to an all-you-can-eat buffet and never feels full, then chances are you are a feaster.

"Secondly, we know that some people have a genetic risk factor for being overweight. It isn't one gene - there are many. Some of them are about personality, some are about appetite, and some about willpower. Those with lots of these 'obesity genes' are the constant cravers."

Chefs and "foodies" are likely to fall into this category, he said.

"Finally, we noticed some people self-medicate with food. They eat when they are unhappy. We call them the emotional eaters."

Having identified the groups, the researchers created different diets for each.

"Feasters" were given a diet designed to stimulate gut hormone levels with high-protein foods such as meat, fish and pulses, and cut out 'high-GI' carbohydrates such as white bread and potatoes.

"Constant cravers" were put on a version of the 5:2 diet, eating no more than 800 calories for two days every week. They could eat what they liked for the other five.

"Emotional eaters" were enrolled in Weight Watchers-style classes, on the theory that what they really needed was social support to prevent them turning to food.

Dr van Tulleken hopes the work will help people understand what causes their weight problems and "spell an end to fad diets".