HEALTH AND FITNESS 

Effect of Exercise on Weight Loss Maintenance 

Obesity is a major issue in Canada, where 59 per cent of adults are overweight, including 23 per cent who are obese, according to Statistics Canada. Overweight is defined as having a body mass index (BMI - calculated as weight in kilograms divided by height in meters squared - an approximation of body fat based on height and weight) - of more than 25, while a BMI of more than 30 indicates obesity.

A Research report published in the Archives of Internal Medicine (July 28) said that in addition to limiting calories, overweight and obese women must exercise substantially more than was previously recommended.

Dr John Jakicic, of the University of Pittsburgh, and his team spent two years on the study.

Between December 1, 1999, and January 31, 2003, 201 overweight and obese women (with BMI of 27 to 40; age range, 21-45 years) with no contraindications to weight loss or physical activity were recruited from a hospital-based weight loss research centre.

Participants were assigned to 1 of 4 behavioural weight loss intervention groups. They were randomly assigned to groups based on physical activity energy expenditure (1000 vs 2000 kcal/wk) and intensity (moderate vs vigorous). Participants also were told to reduce intake to 1200 to 1500 kcal/d. A combination of in-person conversations and telephone calls were conducted during the 24-month study period.

The addition of 275 mins/wk of physical activity, in combination with a reduction in energy intake, is important in allowing overweight women to sustain a weight loss of more than 10%. Interventions to facilitate this level of physical activity are needed.

While women in various groups lost weight, only those who exercised more than 55 minutes a day, five days a week, managed to keep the weight off two years later.

"The less they exercised the less weight they lost and the less they kept off," said Dr John Jakicic, who led the study. "It seemed like this magic number of 275 [minutes a week] is what really made a difference."

"We really wanted to delve into the issues around how much you might really need to do to keep this weight off long term," Dr. Jakicic said. "This study sheds some clear light on what those numbers need to be."

Before this study, health professionals often recommended that people exercise for a minimum of 30 minutes, five days a week. But that level is helpful only for those trying to maintain their health, Dr. Jakicic said, and is not effective for those who have managed to lose a large amount of weight and are trying to keep that weight off.

"There's been so much about the Atkins diet and the Zone diet and surgery," Dr. Jakicic said. "But even people who have the surgery gain weight again without a major lifestyle change."

Dr. Jakicic does not believe people should be discouraged by the exercise level required by his findings, even though working out 55 minutes a day, five days a week, may sound like too punishing a regimen.

"This shouldn't be discouraging. It can be done," he said. "They were able to find ways to make it work with their lifestyle."