London: It`s bad news for overweight people. A 55-year study in Britain has found out that once people gain weight, they can never return to their original size.
Of the 12 million Britons who diet every year, less than 10 percent succeed in losing significant amounts of weight - with most putting it back on within a year.
The national survey by the Medical Research Council followed 5,362 men and women since their birth in 1946, and 20,000 people born in 1958, the Daily Express reported.
The study measured weight and blood pressure and assessed the lifestyles of the people.
"Both groups began increasing in weight in the 1980s and since then people have been increasing in mass all through life," Rebecca Hardy of the council was quoted as saying.
"For men it goes up steadily through life. For women it starts slowly and accelerates in the mid-30s. Once people become overweight they continue relentlessly upwards - hardly ever going down."
The study, however, adds that dieting has its own benefits.
People who try to lose weight tend to eat better and exercise more, leading to increased fitness and lower blood pressure.
The latest health survey in Britain says that in 2009, 14 percent of children and 25 percent of adults were obese.