Resistance Training and Milk-Substitution Enhance Body Composition and Bone Health in Adolescent Girls

Abstract

Background: Increased soft-drink consumption has contributed to poor calcium intake with 90% of adolescent girls consuming less than the RDA for calcium. Purpose/objectives: The purpose of this investigation was to determine the independent and additive effects of two interventions (milk and resistance training) on nutrient adequacy, body composition, and bone health in adolescent girls. Methods: The experimental design consisted of four experimental groups of adolescent girls 14-17 years of age:A few significant differences were observed at baseline between the groups for subject characteristics. Testing was performed pre and post-12 week training period for all groups. Milk was provided (3, 8 oz servings) for both the MRT and the M groups. The MRT group and the RT groups performed a supervised periodized resistance training program consisting of supervised one-hour exercise sessions 3 d/wk (M, W, F) for 12 wk. Baseline dietary data was collected utilizing the NUT-P-FFQ and/or a 120 item FFQ developed by the Fred Hutchinson Cancer Research Center (Seattle, Washington). Body composition was measured in the morning after an overnight fast using dual-energy X-ray absorptiometry (DXA) with a total body scanner (Prodigy TM , Lunar Corporation, Madison, WI). A whole body scan for bone density and lumbar spine scans were performed on all subjects. Maximal strength of the upper and lower body was assessed via a one-repetition maximum (1-RM) squat and bench press exercise protocols. Significance was set at P 0.05. Results: Significant differences in nutrient intakes between groups generally reflected the nutrient composition of milk with greater intakes of protein and improved nutrient adequacy for several B vitamins, vitamin A, vitamin D, calcium, magnesium, phosphorus, potassium, and zinc. Mean calcium intake was 758 and 1581 mg/d, in the non-milk and milk groups, respectively, with 100% of girls in the milk groups consuming > RDA of 1300 mg/d. There were no effects of milk on body composition or muscle performance, but resistance training had a main effect and significantly increased body mass, lean body mass, muscle strength, and muscle endurance. There was a main effect of milk and resistance training on several measures of bone mineral density (BMD). Changes in whole body BMD in the M, RT, MRT, and CON were 0.45, 0.52, 1.32, and À0.19%, respectively (P < 0.01). Conclusions: Over the course of 12 weeks the effects of 1300 mg/d of calcium in the form of fluid milk combined with a heavy resistance training program resulted in the additive effects of greater nutrient adequacy and BMD in adolescent girls. While further studies are needed, combining increased milk consumption with resistance training appears to optimize bone health in adolescent girls.

The association between sugar-sweetened beverages and milk intake with emotional and behavioral problems in children with autism spectrum disorder

“…Milk is considered beneficial for child growth and development as it is an excellent source of essential nutrients ( 18 ). Previous studies showed that milk intake might reduce the risk of chronic diseases such as overweight and obesity ( 19 ), metabolic syndrome ( 20 ), high-blood pressure ( 21 ), as well as improve bone health ( 22 ) and sleep satisfaction ( 23 ). A few studies showed that compared to TD children, children with ASD aged 4–10 years have less frequent milk intake ( 24 , 25 ).…”

The inverse relationship between fatness and bone mineral content is mediated by the adolescent appendicular skeletal muscle mass index: The Cogni-Action Project

“…Adolescents with a higher level of physical activity present better ASMI and lower body fat percentage than those with lower levels of physical activity ( 60 ). Hence, physical activity enhances the development, growth, and quality of bone tissue by biomechanical traction when the muscle is subjected to external loads such as resistance training reported in children, adolescents, and adults ( 61 , 62 ). For instance, myostatin (i.e., myokine produced and released by myocytes that acts on muscle cells to inhibit muscle growth) is regulated by physical activity and, in both animal and human studies, reduces its expression and increases bone turnover, leading to an increase in total bone mass ( 63 ).…”

“…This concern may be even more critical in overweight/obese girls because they displayed higher intramuscular fat (lower muscle density) and low lean mass than their normal-weight lean peers ( 67 ). Thereby, increasing ASMI through physical activity (i.e., resistance training) would help to increase bone quality through fat reduction ( 62 , 68 , 69 ). This suggestion has practical applicability, as a meta-analysis ( 70 ) that evaluated the effect of interventions with high-intensity physical exercise and sports mini-games at school showed that girls are more responsive to increasing bone mineral density than boys.…”

Physical and Emotional Repercussions of Pregnancy during Adolescence

“…Therefore, as competition for nutrients between mother and fetus in pregnancies occurs when mothers are still growing, pregnancy may limit maternal growth [7,23,24]. Many adolescents have poor diet quality and poor knowledge of appropriate nutrition; these habits may not change during pregnancy as reduce ingestion of milk and dairy products, and increased soft drinks consumption which has contributed to poor calcium intake [4,25,26].…”