Research carried out by Indiana University in the US has revealed that an increased amount of exercise may be more beneficial to some people than to others in tackling obesity.

The study - published in the Journal of Epidemiology and Community Health - was conducted by Dong-Chul Seo, an obesity expert and an associate professor at the university.

It is the first population-based study that shows a graded relationship between the total amount of leisure-time physical activity (LTPA) and obesity.

A study sample of 12,227 people was drawn from 1999 to 2006 data from the US National Health and Nutrition Examination Survey (NHANES).

The sample of 20- to 64-year-olds found that obesity rates generally declined as the amount of weekly LTPA increased.

However, the decline was not necessarily the same for all participant groups.

White women saw the steepest decreases in obesity rates, particularly when they met the minimum national guidelines for physical activity - they had an obesity rate of 27.7 per cent if they met guidelines, compared to 40.6 per cent if they engaged in no LTPA.

In contrast, Hispanic and African American women who met MET guidelines had obesity rates of 34.5 and 50 per cent respectively, which increased to 41.5 and 51 per cent when they had no LTPA.

Men were also worse off than white women. They had obesity rates of 29.8 per cent when meeting MET and 34.1 per cent for those with no LTPA.

Seo said: "The majority of health professionals, even researchers, say the more LTPA you engage in, the less likely it is you'll get obese. This is true, but it's probably only applicable to white women and some white men."

According to Seo, men and hispanic women are more likely than white women to have manually demanding jobs, which could affect the amount of LTPA they accumulate - with higher levels of occupational physical activity (OPA), LTPA may account for a smaller proportion of total daily energy output than among white women.

This could lead to an attenuated relationship between LTPA and the prevalence of obesity.

This notion is supported by examining the relationship between OPA and obesity.