NEW ORLEANS - When some people increase their physical activity, they also step up their eating, according research presented this week at the annual meeting of the Obesity Society, an organization of weight-control professionals.

They still lose weight from exercising more but not as much as they might have, says Timothy Church, director of preventive medicine research at Pennington Biomedical Research Center in Baton Rouge.

He followed the progress of 324 post-menopausal women who were overweight or obese. The women were prescribed different amounts of exercise and told not to diet. During their workouts, they were closely supervised with heart-rate monitors, step counters and other measures.

Findings after six months: • Those who did an average of 73 minutes of physical activity a week lost about 3 pounds from the exercise alone, which was what was expected.

• Those who did about 136 minutes of exercise a week lost a little over 4 pounds, also expected.

• But those who exercised 190 minutes a week lost about 3 pounds when they should have dropped about 6 pounds. Some of these women admitted they were eating more, Church says.

"Some people think the exercise gives them carte blanche to eat what they want," Church says. "It doesn't take that many calories to overcompensate for the gains they made through exercise. The bottom line if you want to lose weight, you'd better focus on both diet and exercise."