An April 2010 study is shedding new light on what exactly it takes to maintain a healthy weight. The objective of the study, “Physical Activity and Weight Gain Prevention” (JAMA, April 2010) was to “To examine the association of different amountsof physical activity with long-term weight changes among womenconsuming a usual diet”.
“Because the average U.S. adult gains weight with age, developing ways to prevent unhealthful weight gain would help them avoid having to lose weight and then trying to maintain that loss. Compared with the vast body of research on the treatment of overweight and obese individuals, little research exists on preventing weight gain.The amount of physical activity needed to prevent long-term weight gain is unclear,” study authors reported, according to Science Daily. Given that one in three Americans are currently overweight, and an equal number obese, the study’s goal to seek preventative measures could help the upcoming generations with the battle of the bulge as they age.
The study included 34,079 women, and followed them for a total of 15 years – 1992 to 2007. The women reported their physical activity levels and weight at the start of the study and then again at year 3, 6, 8, 10, 12 and 13. The women were given no caloric restrictions or dietary instructions, and only had to report their physical activity levels, not their diet.
Researchers used the women’s self-reported input to classify them based on their metabolic equivalent (MET) hours a week of exercise. The women fell into one of three groups: less than 7.5 MET hours per week, 7.5 to under 21 MET hours per week, and 21 or more MET hours per week.
In this study, the researchers discovered the biggest impact of exercise on the women who were already at a healthy weight. The women in this group had a BMI of 25 or lower at the time the study began.
“A total of 4,540 women (13.3 percent) with a BMI lower than 25 at study start successfully maintained their weight by gaining less than 5.1 lbs. throughout. Their [average] activity level over the study was 21.5 MET hours per week ([approximately] 60 minutes a day of moderate-intensity activity),” Science Daily credits the researchers as writing.
The overweight and obese groups did not see the same positive results that the ideal weight group did.
According to the report, researchers concluded that, “Among women consuming a usual diet, physicalactivity was associated with less weight gain only among womenwhose BMI was lower than 25. Women successful in maintainingnormal weight and gaining fewer than 2.3 kg over 13 years averaged approximately60 minutes a day of moderate-intensity activity throughout the study.”
Science Daily: Amount of Physical Activity Needed to Prevent Long-Term Weight Gain
Journal of the American Medical Association: Physical Activity and Weight Gain Prevention