Overweight young women were also more likely to suffer disadvantage than men.
The study from the Harvard School of Public Health, Massachusetts, says that obesity has important social and economic consequences that are greater than those of many other chronic diseases, including asthma and diabetes.
As part of a much bigger study, 10,000 young people aged 16 to 24 were randomly selected in 1981 and three-quarters of them followed up seven years later. At the beginning of the survey, 370 were found to be overweight - that is, more than 20 per cent above their desirable weight for their height. At the same time a large amount of information was collected on their health, lifestyle and mental well-being.
Dr Steven Gortmaker, of the Department of Health and Social Behaviour at Havard, and colleagues say in the latest edition of the New England Journal of Medicine that being overweight is an increasingly prevalent nutritional disorder in the US.
'Numerous health risks have been associated with adolescent overweight including hypertension, respiratory disease, several orthopaedic disorders, diabetes and elevated serum lipid concentrations (high blood fat levels),' Dr Gortmaker says.
He says there is evidence to show that fat people are 'highly stigmatised' in the US and that unlike colour or sex, weight is thought to be under voluntary control so that fat people are held responsible for their condition and for changing it. 'The perception that physically overweight people are less attractive could lead to lower rates of marriage.'
The researchers believe that discrimination accounts for most of their findings. They found that the fat young people experienced a 10 per cent increase in prevalence of poverty - and had a average of dollars 3,037 less to spend a year.
Only 10 per cent of them completed college courses compared with 23 per cent of the non-overweight, and 40 per cent of the overweight had married compared with 48 per cent of those of normal weight.
The researchers looked for, but did not find, evidence that the fat group had lower self-esteem.
Dr Gortmaker believes that the discrimination is so evident that there is a case for overweight people to be protected by the Disabilities Act, new US legislation which prohibits discrimination in employment.
In Britain, obesity is also causing increasing concern. It has been estimated that 4-5 per cent of 11-year-olds carry more than twice the normal body weight for their height and that more than half of them will be overweight by the time they are 26.
Other studies have shown that since 1972 not only are children taller, but they are also fatter. British men and women are also becoming fatter; 13 per cent of men and 15 per cent of women were obese in 1991 compared with 7 per cent and 12 per cent respectively in 1987.