NEW YORK: People who consistently engage in high levels of exercise over the long haul are the most successful at losing weight and keeping it off, a new study shows.

Among a group of overweight men and women participating in an 18-month weight loss programme, those who were still getting 75 minutes of exercise daily a year after the programme ended had lost 12 kilogrammes, compared to 0.8 kg for people who were exercising less.

But only 13 of the 154 people who completed the study were able to sustain this level of activity, Deborah F Tate of the University of North Carolina in Chapel Hill and her colleagues found. "Strategies are needed to help participants maintain high levels of activity over the long-term," she and her colleagues conclude.

The researchers initially assigned 202 people to either a high physical activity group who aimed to burn 2,500 calories per week (equivalent to a 75-minute walk daily) or standard behavioural treatment, including 30 minutes of exercise daily, equivalent to 1,000 calories per week.

Twelve and 18 months later, people in the high activity group had lost significantly more weight than those in the lower activity group.

Although the participants in the high activity group were able to sustain the 2,500 calorie per week exercise goal during the 18-month study, their activity level declined once treatment ended, which resulted in no between-group differences in activity or weight loss at 2.5 years.