Thirty minutes of moderate exercise daily may not trim off the fat after all, a new study says. University of Pittsburgh researchers say it takes at least 55 minutes per day, five days a week, to keep off the pounds. The study followed 200 overweight women, and found that only those who exercised twice as much as normally suggested were able to cut 10% of their weight.
Researchers concluded that exercise time reduced fat more than any other factor, including diet. But other studies are skeptical that diet and exercise can determine body weight in the long run. Studies have shown that each body has a "set point," and tries to keep weight within 10 to 20 pounds of that mark—which may explain why no women in the Pittsburgh study lost much more than 10% of their body fat.