Dairy product consumption is associated with a lowering of linoleic acid within serum TAG in adolescent females with overweight or obesity: a secondary analysis.

Dairy fat is rich in SFA such as palmitic acid (16:0) but low in linoleic acid (18:2n-6). The natural carbon 13 enrichment (δ13C) of 16:0 is higher in dairy fat than in most of the food supply. In adults, serum levels of pentadecanoic acid (15:0) and heptadecanoic acid (17:0) are recognised as biomarkers of dairy intake. In adolescents, no study has evaluated serum fatty acid levels or δ13C in response to chronic dairy consumption. The objectives of this study were to evaluate whether increased dairy product consumption can modulate (1) serum fatty acid levels and (2) 16:0 δ13C in adolescents with overweight/obesity who followed a 12-week weight management programme. This secondary analysis of a randomised control trial included two groups of adolescent females: recommended dairy (RDa; n 23) and low dairy (LDa; n 23). The RDa group was given 4 servings/d of dairy products while the LDa group maintained dairy intakes at ≤ 2 servings/d. Blood was sampled before and after the intervention. Lipids were extracted and separated, and fatty acids were quantified by GC. Isotope ratio MS was used to assess 16:0 δ13C. There were no group differences on serum changes of 15:0 or 17:0. Within TAG, 18:2n-6 was lowered by 7·4 % only in the RDa group (P = 0·040). The difference in delta 16:0 δ13C between the LDa and RDa groups did not reach statistical significance (P = 0·070). Reductions in serum 18:2n-6 by dairy consumption could have positive health implications, but more studies are needed to confirm this assertion.

Integrating needs-supportive delivery into a laboratory-based randomised controlled trial for adolescent girls with overweight and obesity: Theoretical underpinning and 12-week psychological outcomes.

When designing efficacy trials, researchers have a responsibility to "do no harm" and to "do good". Given the psychological vulnerability of adolescent girls with overweight and obesity, it is important to consider the implications of participating in weight-related research studies. We investigated psychological outcomes from a 12-week laboratory-based randomised controlled trial aimed at improving body composition and bone health in adolescent girls with overweight and obesity. Sixty-three participants were randomised to three groups (Recommended dairy diet plus exercise (RDa, n = 24); Low dairy diet plus exercise (LDa, n = 25); no-intervention control (n = 14)). Self-Determination Theory-informed strategies were applied in both intervention groups to foster motivation and enhance psychological wellbeing. Motivation, perceived competence and self-perceptions were measured at 0 and 12 weeks. Fifty-four participants (24 RDa, 23 LDa, 7 Control) provided complete psychological data. There were no between group differences in 0- to 12-week change in motivation, perceived competence or global self-worth. Both intervention groups showed significant improvements in physical self-worth (p = 0.001), body satisfaction (p = 0.002) and perceived physical conditioning (p = 0.002), compared with the control group. A theory-informed, laboratory-based diet and exercise intervention produced favourable psychological outcomes for adolescent girls with overweight and obesity.

Neutral Effect of Increased Dairy Product Intake, as Part of a Lifestyle Modification Program, on Cardiometabolic Health in Adolescent Girls With Overweight/Obesity: A Secondary Analysis From a Randomized Controlled Trial.

Background: The presence of obesity and some cardiometabolic disease risk factors in childhood and adolescence track into adulthood. Intake of dairy products has been shown to be inversely related to adiposity and cardiometabolic variables in youth. However, limited research has examined cardiometabolic disease risk factors following increased dairy product consumption as part of a lifestyle modification intervention in youth with overweight/obesity. This secondary analysis aimed to determine whether 12 weeks of increased dairy consumption, as part of a lifestyle modification program, affects cardiometabolic variables in adolescent females (range: 10-18 years) with overweight/obesity (BMI > 85th centile). Methods: Participants were randomized into two groups: higher dairy intake (RDa; four servings/day [to reflect previous Canada's Food Guide recommendations]; n = 23) or low dairy intake (LDa; 0-2 servings/day; n = 23). Both RDa and LDa participated in a 12-week, eucaloric, lifestyle modification intervention consisting of exercise training, and nutritional counseling. Adiposity (percent body fat [%BF]), dietary intake, and measures of cardiometabolic health were measured pre- and post-intervention. Results: There were no significant changes over time within groups or differences over time between groups for triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL), TC/HDL ratio, low-density lipoprotein cholesterol (LDL), glucose, insulin, homeostatic model assessment of insulin resistance, adiponectin, and tumor necrosis factor alpha (TNF-α) (main effects of time and interactions, p > 0.05). Leptin decreased over the 12-week lifestyle intervention in both groups (main effect of time, p = 0.02). After combining the groups (n = 46), significant correlations were found between change in %BF and change in some cardiometabolic variables (HDL [r = -0.40], TC/HDL ratio [r = 0.42], LDL [r = 0.36], and TNF-α [r = 0.35], p < 0.05). After controlling for change in dairy product intake, the correlations were unchanged. Conclusion: Our findings demonstrate that increased dairy product consumption, as part of a lifestyle modification, weight management intervention, had a neutral effect on cardiometabolic disease risk factors in adolescent females with overweight/obesity. Change in dairy product intake did not influence the relationships between change in adiposity and change in cardiometabolic variables. Future research designed to primarily assess the effect of increased dairy product consumption on cardiometabolic disease risk factors in this population is warranted. Clinical Trial Registration: Clinicaltrials.gov; NCT#02581813.

Cytokines, Adipokines, and Bone Markers at Rest and in Response to Plyometric Exercise in Obese vs Normal Weight Adolescent Females.

Background: In adults, excess adiposity has been associated with low-grade, chronic inflammation and compromised bone health, but less is known about these linkages in children. The purpose of this study was to compare the circulating levels of inflammatory cytokines, adipokines, osteokines, and bone markers at rest and in response to plyometric exercise between obese and normal weight adolescent females. Methods: Ten normal weight (BMI = 21.3 ± 2) and 10 obese (BMI = 32.9 ± 4), postmenarcheal females, aged 13-17 years, performed one bout of plyometric exercise (5 circuits; 120 jumps). Blood samples were taken at rest, 5 min, 1 h, and 24 h post-exercise. Tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), insulin, leptin, osteocalcin, carboxy-terminal telopeptide (CTX), sclerostin, and parathyroid hormone (PTH) were measured in serum. Results: Cytokines were not different between groups at rest or over time with IL-6 increasing (+31%; p = 0.04) 5 min post-exercise and TNF-α decreasing (-9%; p = 0.001) 1 h post-exercise. Insulin and leptin were higher in the obese compared to the normal weight females. In both groups, insulin significantly increased 5 min post-exercise but remained elevated 1 h post-exercise only in the obese group. Leptin did not change in response to exercise. Osteocalcin was lower in the obese group across time and increased (+12%; p = 0.02) 24 h post-exercise in both groups. CTX was similar between groups at rest and decreased (-24%; p < 0.001) 1 h post-exercise. Sclerostin was similar between groups at rest, but there was a significant interaction reflecting a significant increase (+29%; p = 0.04) 5 min post-exercise in the obese group and a non-significant decrease (-13%; p = 0.08) in normal weight controls. PTH increased 5 min post-exercise, dropped 1 h post-exercise to lower than pre-exercise, and returned to baseline 24 h post-exercise in both groups. Conclusion: Obese adolescent females from our study had no evidence of resting inflammation or differences in bone resorption but show blunted bone formation when compared to normal weight controls. The direction and temporal changes in inflammatory cytokines, adipokines, and bone turnover markers to exercise were similar in both groups, reflecting an overall bone anabolic response for most biomarkers, except sclerostin, which increased only in the obese females immediately post-exercise, suggesting a different systemic regulation of sclerostin depending on adiposity.

Increased dairy product consumption as part of a diet and exercise weight management program improves body composition in adolescent females with overweight and obesity-A randomized controlled trial.

BACKGROUND: Exercise can improve body composition in adolescents and adults with overweight/obesity. Consumption of dairy foods, as part of a healthy lifestyle program, can also promote favourable body composition changes in adults with overweight/obesity. However, the few studies examining these combined effects on body composition in adolescents are inconclusive. OBJECTIVE: To determine whether increased dairy product consumption, as part of a lifestyle modification program featuring exercise training and dietary guidance promotes favourable body composition changes in adolescent females with overweight/obesity. METHODS: Fifty-four participants (age: 14.8 ± 2.2y; BMI percentile: 95th ± 6) assigned to three groups completed the study. There were two experimental groups: recommended dairy (RDa; n = 24) and low dairy (LDa; n = 22), and a no-intervention control group (Con; n = 8). RDa and LDa participated in a 12-week, eucaloric, lifestyle modification intervention consisting of mixed-mode exercise (3x/week), and nutritional counselling. RDa was provided 4 servings/day of dairy foods, while LDa and Con maintained habitually low intakes (0-2 servings/day). Body weight/composition, waist/hip circumference, cardiovascular fitness and food intake were assessed at weeks 0 and 12. RESULTS: Weight did not significantly change in any group. RDa significantly decreased fat mass (FM) and increased lean mass (LM) more than LDa and Con (FM: -1.3 ± 2.1 kg, -1.1 ± 2.0 kg, 0.8 ± 1.8 kg; LM: 1.5 ± 1.9 kg, 0.7 ± 1.6 kg, 0.5 ± 1.4 kg, respectively). LDa also significantly decreased FM and increased LM more than Con (P < .005; all interactions). CONCLUSION: The inclusion of dairy foods in the diet of adolescent females with overweight/obesity, as part of a diet and exercise intervention, favourably improves body composition in the absence of weight loss.

Dairy product intake decreases bone resorption following a 12-week diet and exercise intervention in overweight and obese adolescent girls.

BACKGROUND: We examined whether increased dairy intake was associated with changes in the levels of bone-related biochemical markers in overweight/obese adolescent girls undergoing a 12-week diet and exercise intervention. METHODS: Thirty-five girls were assigned to a low dairy group (LDa; 0-2 servings/day; n = 16) or a higher dairy group (RDa; 4 servings/day; n = 19). Morning, fasted/resting blood samples were collected before and after the intervention and serum concentrations of procollagen-type-1-N-terminal-propeptide (P1NP), ß-isomerized-C-terminal-cross-linking-telopeptides (ß-CTX), osteocalcin (OC), 25-hydroxyvitamin-D, sclerostin and parathyroid hormone were measured. RESULTS: At baseline, there were no significant differences between groups in any bone variable. Changes (∆) over time in ß-CTΧ (p = 0.035; interaction) and OC (p = 0.015; interaction) were significantly different between groups characterized by decreases in RDa and increases in LDa. P1NP and P1NP:ß-CTX ratio decreased in both groups (main time effects: p = 0.003, p = 0.041, respectively). ∆ß-CTX (r = -0.37; p = 0.028) and ∆OC (r = -0.39; p = 0.021) were correlated with average number of dairy servings consumed during the study and with each other (r = 0.45; p = 0.006). ∆OC was not correlated with ∆P1NP (r = 0.19; p = 0.27). CONCLUSIONS: Our results suggest that the osteogenic response to a diet and exercise program in this population can be improved with increased dairy intake via a decrease in bone resorption. IMPACT: We demonstrated that bone resorption significantly decreased over the intervention period in the group consuming adequate levels of dairy products compared to the group consuming little to no dairy products. Change in bone resorption was negatively correlated with average number of dairy servings consumed during the study. Our results suggest that the osteogenic response to a diet and exercise program in this population can be improved with increased dairy intake via a decrease in bone resorption. This is the first study to date to assess changes in bone marker status following a lifestyle intervention with exercise and different intakes of dairy products in a sample of OW/OB adolescent girls. We provide evidence that increased dairy product intake is associated with beneficial changes in circulating levels of bone-related biochemical markers in these girls undergoing a 12-week lifestyle (nutrition counseling and exercise training) intervention program. The main impact of our work relates particularly to the recent changes to Canada's food guide. Using the old recommendations, we demonstrated that the inclusion of 3-4 servings of mixed dairy foods per day improved bone health (primarily as a decrease in resorption) in OW/OB adolescent girls and that this level of dairy product intake appears appropriate and should still be encouraged for this age group. We also demonstrated that adolescent girls, a group that usually does not sufficiently consume dairy products, also improved their BMI percentile and nutrient intake with the inclusion of dairy products in their diets.