Menstrual abnormalities are associated with negative energy balance and reduced energy expenditure (REE). To examine this relationship in elite adolescent aesthetic athletes, 3 groups of females (aged 15-18 years) were studied: 10 oligo/amenorrheic athletes (OA), 11 eumenorrheic athletes (EA), and 8 non-athlete controls (C). Components of energy balance, body composition, dietary restraint, pubertal maturation, and luteal phase salivary progesterone were assessed in all groups. Both groups of athletes had a later age of menarche and lowerpubertal development score compared to the non-athletes (p < .05). With the exception of salivary progesterone (ng/ml; OA = 0.15±0.01 <EA = 0.29± 0.1 and C = 0.30 ± 0.13, /p = .007), there were no differences between the athlete groups. Energy balance (kcal/d) in the OA group was lower (−290 ± 677) compared to either EA (−5±461) or C (179 ± 592) but did not reach significance (p = .24). Dietary energy intake and absolute REE (kcal/d) were not different among groups, despite detectable differences in reproductive status, and thus could not be attributed to differences in energy balance or REE.
Karen J. Reading, Linda J. McCargar, and Vicki J. Harber
Geoff D.C. Ball, J. Dru Marshall, and Linda J. McCargar
We investigated whether body composition, physical activity, physical inactivity, and cardiorespiratory fitness explained the presence of risk factors for cardiovascular disease (CVD) and type 2 diabetes in youth. Eighty-three obese children (6–12 years old) were classified as either low health risk (LHR; n = 30) or high health risk (HHR; n = 53) based on the absence/presence of metabolic risk factors that included measures of dyslipidemia, insulin resistance, and elevated blood pressure. Along with demographic and anthropometric data, body composition, physical activity, physical inactivity, and cardiorespiratory fitness variables were assessed. Risk factor clustering was evident in this sample with 24/83 (29%) possessing at least 2 risk factors. Percent body fat did not differ between the LHR (38.5%) and HHR (39.8%) groups, but total fat mass, total fat-free mass, and central body fat mass were greater in the high health risk group. The strongest predictor for the presence of risk factors was central body fat accumulation. Physical activity, physical inactivity, and cardiorespiratory fitness were unable to predict metabolic risk. Overall, we found that risk factors for CVD and type 2 diabetes were common and that body fat mass and central body fat distribution, in particular, were more important than physical activity, physical inactivity, and cardiorespiratory fitness in predicting metabolic risk in obese children.
Scott C. Forbes, Linda McCargar, Paul Jelen, and Gordon J. Bell
The purpose was to investigate the effects of a controlled typical 1-day diet supplemented with two different doses of whey protein isolate on blood amino acid profiles and hormonal concentrations following the final meal. Nine males (age: 29.6 ± 6.3 yrs) completed four conditions in random order: a control (C) condition of a typical mixed diet containing ~10% protein (0.8 g·kg–1), 65% carbohydrate, and 25% fat; a placebo (P) condition calorically matched with carbohydrate to the whey protein conditions; a low-dose condition of 0.8 grams of whey protein isolate per kilogram body mass per day (g·kg–1·d–1; W1) in addition to the typical mixed diet; or a high-dose condition of 1.6 g·kg–1·d–1 (W2) of supplemental whey protein in addition to the typical mixed diet. Following the final meal, significant (p < .05) increases in total amino acids, essential amino acids (EAA), branch-chained amino acids (BCAA), and leucine were observed in plasma with whey protein supplementation while no changes were observed in the control and placebo conditions. There was no significant group difference for glucose, insulin, testosterone, cortisol, or growth hormone. In conclusion, supplementing a typical daily food intake consisting of 0.8 g of protein·kg–1·d–1 with a whey protein isolate (an additional 0.8 or 1.6 g·kg–1·d–1) significantly elevated total amino acids, EAA, BCAA, and leucine but had no effect on glucose, insulin, testosterone, cortisol, or growth hormone following the final meal. Future acute and chronic supplementation research examining the physiological and health outcomes associated with elevated amino acid profiles is warranted.
John C. Spence, Chris M. Blanchard, Marianne Clark, Ronald C. Plotnikoff, Kate E. Storey, and Linda McCargar
The purposes of this study were to determine if a) gender moderated the relationship between self-efficacy and physical activity (PA) among youth in Alberta, Canada, and, alternatively b) if self-efficacy mediated the relationship between gender and PA.
A novel web-based tool was used to survey a regionally diverse sample of 4779 students (boys = 2222, girls = 2557) from 117 schools in grades 7 to 10 (mean age = 13.64 yrs.). Among other variables, students were asked about their PA and self-efficacy for participating in PA.
Based upon a series of multilevel analyses, self-efficacy was found to be a significantly stronger correlate of PA for girls. But, boys had significantly higher self-efficacy compared with girls, which resulted in significantly more PA.
Findings suggest self-efficacy is an important correlate of PA among adolescent girls but that boys are more physically active because they have more self-efficacy for PA.
Catrine Tudor-Locke, Nicola Lauzon, Anita M. Myers, Rhonda C. Bell, Catherine B. Chan, Linda McCargar, Mark Speechley, and N. Wilson Rodger
To compare the effectiveness of a theory-based lifestyle physical activity (PA) program delivered to individuals with type 2 diabetes in diabetes education centers by professionals and peers.
Changes over 16 weeks in PA (steps/day) and related variables (weight, waist girth, resting heart rate, systolic and diastolic blood pressures) were compared (RMANOVA) for two groups: 157 participants led by 13 different professionals versus 63 participants led by 5 peer leaders.
Overall, the 81 male and 139 female participants (age = 55.7 ± 7.3 years, BMI = 35.2 ± 6.6) showed an incremental change of 4,059 ± 3,563 steps/day, which translates into an extra 37 minutes of daily walking (P < .001). Statistically significant improvements were also seen in weight, waist girth, and blood pressure (all P < .001) and resting heart rate (P < .05). There were no significant differences in outcomes between professional and peer-led groups.
A theory-based behavior modification program featuring simple feedback and monitoring tools, and with a proven element of flexibility in delivery, can be effective under real-world conditions while addressing inevitable concerns about resource allocation. Program delivery by peer leaders, in particular, could address a potential obstacle to dissemination by helping to alleviate existing high caseload demands on diabetes educators.