• The effect of increased dairy consumption during one week of intense training on serum bone markers of adolescent female athletes

      McKee, Katherine; Applied Health Sciences Program
      While high-impact exercise training typically has a positive effect on bone, intensified training during adolescence, the period of rapid growth and peak bone acquisition, could potentially have an opposite effect. Dairy foods contain bone-supporting nutrients (i.e., calcium) that are crucial to the structural integrity and strength of bone. In this study, 13 female adolescent soccer players (14.3 ± 1.3y) participated in a cross-over, randomized, double-blind trial examining the effects of Greek yogurt (GY) consumption on bone biomarkers during a one-week period of intensified training. The study took place over two intervention weeks, which consisted of a pre-training assessment day, 5-days of consecutive, intense soccer training and a post-training assessment day. Participants completed both the GY condition, and a carbohydrate isocaloric placebo control pudding condition (CHO) condition in random order, 4 weeks apart. Fasted, resting blood samples were collected in the morning at pre- and post-training sessions during each intervention condition. Total osteocalcin (tOC), undercarboxylated osteocalcin (unOC), carboxyl-terminal telopeptide of type 1 collagen (CTX), osteoprotegerin (OPG), and receptor activator nuclear factor kappa-β ligand (RANKL) were measured in serum. Results showed no significant effects for time (from pre- to post-training) and condition, and no interaction in tOC, CTX, OPG, RANKL and OPG/RANKL ratio. There was an interaction (p=0.011) for unOC, which decreased significantly at the end of the intense training period in the GY condition, but not in the CHO condition (-26% vs -3%, respectively). Relative unOC, expressed as a percentage of tOC, also reduced post-training (-16%), but with no differences between intervention conditions. These findings suggest that high-impact intense training had no direct catabolic impact on bone metabolism, at least in the short-term, and thus, GY added no benefit beyond that of the isocaloric CHO control pudding.
    • Effects of dairy consumption and exercise on body composition in overweight/obese adolescent females: The I.D.E.A.L. (Improving Diet, Exercise, and Lifestyle) for Adolescents Study

      Calleja, Melissa; Applied Health Sciences Program
      Exercise training is known to decrease fat mass and increase lean mass in adolescents and adults. In adults, the consumption of dairy foods, as part of a lifestyle intervention, can promote favourable body composition changes. However, results of the few studies examining the combined effects of exercise and dairy consumption on body composition in adolescents are inconclusive. The purpose of our study was to determine whether increased dairy consumption, along with structured exercise training and dietary guidance within a weight management program, can promote favourable changes in body composition, anthropometry and cardiovascular fitness in overweight/obese adolescent females. Sixty-one adolescent females (age: 14.8±2.2 y; BMI: 29.3±5.1 kg/m2) were randomized to 3 groups: recommended dairy (RDa; n=24); low dairy (LDa; n=22); control (GCon; n=8), and 54 participants completed the study. The RDa and LDa groups participated in a 12-week, individualized, eucaloric, lifestyle modification intervention consisting of mixed-mode exercise 3x/week, and 5 nutritional counselling sessions with a registered dietitian. RDa group was provided 4 servings/day of dairy (as milk, Greek yogurt and cheese), while LDa maintained habitually low intakes of 0-2 servings/day. Seven-day food records were collected at weeks 0 and 12. Body composition, waist/hip circumference, and VO2peak were assessed for all groups at weeks 0 and 12. Both RDa and LDa decreased body fat (-1.7±1.5%, -1.2±1.1%, respectively), fat mass (-1.3±2.1kg, -1.1±2.0kg, respectively) and subcutaneous fat thickness (-12.5±10.0mm, -9.1±9.4mm, respectively) compared with the GCon (0.3±1.3%, 0.8±1.8kg, 3.0±8.0mm, respectively) (p ≤0.002 for all). RDa decreased fat mass (kg) more than LDa (p=0.001). Both RDa and LDa gained more lean mass (1.5±1.9kg, 0.7±1.6kg, respectively) than GCon (0.5±1.4kg). RDa increased lean mass more than LDa (p≤0.001). VO2peak (ml/min/kg) did not differ between groups following the intervention (p=0.093). These findings suggest that the inclusion of a variety of dairy foods in the diet of overweight/obese adolescent girls, as part of a weight management intervention program, is beneficial to the overall improvement in body composition.