EFFECTS OF INCREASING FLUID MILK INTAKE ON BODY COMPOSITION RESPONSES TO RESISTANCE TRAINING IN TEENAGE BOYS

Abstract

Data from animal and human epidemiological and longitudinal studies provide a link between increased availability of calcium with increased lipolysis and decreased fat mass. The purpose of this study was to examine the effects of increasing fluid MILK intake on body composition after a 12-week resistence training program in teenage boys. Twentyeight teenage boys (aged 13–17 yrs) who habitually consumed less than 3 serving of fluid MILK per day were matched and then randomly assigned into either a MILK (n = 14) or JUICE (n = 14) supplementation group. Subjects consumed 240 mL (24 oz) per day of either 1% fluid MILK or JUICE in addition to the their habitual diet. Both groups completed a 12-week periodized heavy-resistance training program consisting of supervised one-hour exercise sessions three days per week utilizing all major muscle groups. Body composition was assessed at 0, 6, and 12 weeks using dual-energy X-ray absorptiometry. Body mass significantly increased in the MILK and JUICE groups from Week 0 to Week 6 (+1.2 and +1.1 kg, respectively) with no further significant changes from Week 6 to Week 12 (−0.1 and +0.7 kg, respectively). Percent body fat significantly decreased in the MILK and JUICE groups from Week 0 to Week 6 (−1.2 and û1.5%, respectively) and there was a further significant decrease in the MILK group from Week 6 to Week 12 (−1.0%) while the JUICE group demonstrated no significant change from Week 6 to Week 12 (+0.1%) Similar to percent body fat, fat mass decreased at Week 6 in both groups but only the MILK group continued to lose fat mass at Week 12. Lean body mass significantly increased to the same extent in the MILK and JUICE groups from Week 0 to Week 6 (+1.9 and +1.9 kg, respectively) with no further significant changes from Week 6 to Week 12 (+0.5 and +0.5 kg, respectively). These findings indicate that heavy resistance training has favorable effects on body composition in teenage males. In addition, increasing fluid milk intake in teenage boys engaged in a resistance training program may lead to further reductions in fat mass, possibly due to higher intake of dietary calcium. Supported by the National Dairy Council, Rosemont, IL.