From Tufts U: Achieving healthy weight in children

http://www.ncbi.nlm.nih.gov/pubmed/22307068

Obesity (Silver Spring). 2012 Feb 6. doi: 10.1038/oby.2012.13. [Epub ahead of print]
Predicting maintenance or achievement of healthy weight in children: the impact of changes in physical fitness.
Hruby A, Chomitz V, Arsenault LN, Must A, Economos CD, McGowan R, Sacheck JM.
Source
Tufts University Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy, Boston, Massachusetts.

Abstract
Physical fitness is often inversely associated with adiposity in children cross-sectionally, but the effect of becoming fit or maintaining fitness over time on changes in weight status has not been well studied in children. We investigated the impact of changes in fitness over 1-4 years of follow-up on the maintenance or achievement of healthy weight among 2,793 schoolchildren who were first measured as 1st-7th graders. Students were classified as "fit" or "underfit" according to age- and gender-specific norms in five fitness domains: endurance, agility, flexibility, upper body strength, and abdominal strength. Weight status was dichotomized by BMI percentile: "healthy weight" (<85th percentile) or "overweight/obese" (≥85th percentile). At baseline, of the 38.3% overweight/obese children, 81.9% (N=875) were underfit. Underfit overweight students were more likely to achieve healthy weight if they achieved fitness (boys: OR 2.68, 95%CI 1.24-5.77; girls: OR 4.67, 95%CI 2.09-10.45). Initially fit overweight children (N=194) were more likely to achieve healthy weight if they maintained fitness (boys: OR 11.99, 95%CI 2.18-65.89; girls: OR 2.46, 95%CI 1.04-5.83). Similarly, initially fit healthy weight children (N=717) were more likely to maintain healthy weight if they maintained fitness (boys: OR 3.70, 95%CI 1.40-9.78; girls: OR 4.14, 95%CI 1.95-8.78). Overweight schoolchildren who achieve or maintain physical fitness are more likely to achieve healthy weight, and healthy weight children who maintain fitness are more likely to maintain healthy weight. School-based policies/practices that support physical fitness may contribute to obesity reduction and maintenance of healthy weight among schoolchildren.