Author: Cooper Rebecca
Date: April 2007
In a world of fad diets and rising incidence of eating disorders, Inger Stallmann-Jorgensen, a research dietician, offers some surprising news. Published in the April issue of The International Journal of Obesity, Stallmann-Jorgensen et al.'s findings show that teenagers who exercised the most and ate the most were the leanest.
Stallmann-Jorgensen and her colleagues studied 661 healthy black and white teens from Augusta, Georgia. They hypothesized that different variables,dietary intake, physical activity, visceral body fat levels, race, and gender, are highly correlated with percent body fat (%bf). To test this hypothesis, researchers recorded the participants' physical activity and food intake over at least four 24-hour periods and performed magnetic resonance imaging scans on 434 of the participants. These scans measured visceral adipose tissue,the fat surrounding abdominal organs,a more accurate predictor of cardiovascular disease and type 2 diabetes than overall body fat; even relatively thin children can have enough visceral fat to be a health problem, Dr. Paule Barbeau, a corresponding author of the paper, says.
Researchers found that a participant's level of physical activity was the only truly correlative variable, although race, visceral body fat, and gender were also highly predictive. For example, female study participants had, on average, 30 %bf (high for females) while males had a healthier 18 %bf.
Since all the teens had relatively poor eating habits, underconsuming fruits and vegetables and overconsuming starches, sugars and salty snacks, dietary content analysis could not be performed. Amount of food intake was considered, instead.
Researchers found that teens who ate the most were often the highest energy consumers. Their physical activity offset their high caloric intake, resulting in the lowest levels of visceral body fat among participants.
Surprisingly, Stallman-Jorgensen et al. also found that some participants who ate the least had the highest %bf. "If you think about teenagers trying to restrict their energy intake," Ms. Stallmann-Jorgensen explains, "they usually are not going to be doing a lot of physical activity to stay at that energy balance because they will be tired." This helps explain why fasting and extreme diets don't seem to work. The fatigue that accompanies a decreased food intake leads to less physical activity. This, in turn, negates whatever caloric advantage one gained by extreme diet restriction.
"The take-home message," Barbeau explains,"[should] be to encourage your child to do as much vigorous physical activity as possible, including at least one hour.on a daily basis."
While these findings may not singularly reverse America's bipolar weight trend, by underscoring the age-old adage of "Eat well, exercise often," they offer some encouragement,and incentive,for moderation.
By Rebecca Cooper