Small weight gain is not associated with development of insulin resistance in healthy, physically active individuals.

UNLABELLED: We investigated whether weight gain alters insulin sensitivity and leptin levels in physically active individuals. Six (5 males and 1 female; age 26.6+/-1.0 years; BMI 21.5+/-0.9, body fat 17.4+/-2.2%) healthy individuals were enrolled in an overfeeding study (caloric surplus 22.5-26.5 kcal/kg/day) to achieve up to 10% weight gain over 4-6 week period with subsequent weight maintenance over additional 2 weeks. The participants were requested to maintain their previous physical activity which in all of them included 45-60 min training sessions at the gym 2-3 times/week. RESULTS: BMI increased to 23.4+/-0.9 (4.4 kg weight gain; p<0.05) and body fat to 21.0+/-2.8% (p < 0.05) over the period of active weight gain and remained stable over the two week period of weight maintenance; fasting plasma glucose and serum insulin remained unchanged; serum leptin nearly doubled (3.8+/-1.0 vs 6.4+/-1.9 ng/ mL; p < 0.05); insulin sensitivity, when expressed per kg of the total body (11.1+/-1.6 vs 12.4+/-2.1 mg/kg/min; p = NS), and lean body mass (13.4+/-1.9 vs 15.7+/-2.6 mg/kgLBM/min; p = NS), did not decrease after weight gain. On the contrary, insulin action had improved in 5 out of 6 individuals. In conclusion, the data presented in this preliminary report indicate that a small weight gain due to overfeeding in lean, healthy, physically active individuals is associated with rise in circulating leptin levels but not with worsening of insulin action.