Scientists at the University of Pittsburgh found that overweight middle-aged people who walked briskly for 30 to 60 minutes a day lost 7 pounds in a year and a half, while similar adults who didn’t exercise consistently gained several pounds in that time.

In the second study, University of North Carolina researchers did an analysis of data on young adults, ages 18 to 30, over a 15-year period and found those who walked four or more hours a week were the least likely to gain weight as they aged.

This adds to a growing body of evidence on the importance of exercise for weight control, says John Jakcic, director of the University of Pittsburgh’s Physical Activity and Weight Management Research Center.

All participants were advised to eat a healthy diet but told not to restrict their calories.  About 75% chose to walk for exercise.  At the end of 18 months:

• 40% of participants gained weight, an average of 7 pounds.  Those most likely to gain were people who did not exercise regularly.
• 60% lost weight, an average of 7 pounds.  These were people in either of the groups who did about 40 minutes of activity seven days a week.

“This is a weight difference of about 14 pounds between people who exercised and those who didn’t,” Jakcic says.

Penny Gordon-Larson, an assistant professor of nutrition at North Carolina, analyzed data on 5,000 young adults over 15 years.  She found that a slightly overwoman who walked two extra hours each week over 15 years gained 9 pounds less in that time than a similar woman who didn’t walk that much. 

 Women who walked an extra four hours each week gained 18 pounds less over that time than women who didn’t move that much.  The effects were similar for men.

“Extra walking prevents weight gain at a time of life when many people are gaining,” she says.