Ellen M. Evans

A Moderate-Protein Diet Produces Sustained Weight Loss and Long-Term Changes in Body Composition and Blood Lipids in Obese Adults

Diets with increased protein and reduced carbohydrates (PRO) are effective for weight loss, but the long-term effect on maintenance is unknown. This study compared changes in body weight and composition and blood lipids after short-term weight loss (4 mo) followed by weight maintenance (8 mo) using moderate PRO or conventional high-carbohydrate (CHO) diets. Participants (age = 45.4 +/- 1.2 y; BMI = 32.6 +/- 0.8 kg/m(2); n = 130) were randomized to 2 energy-restricted diets (-500 kcal/d or -2093 kJ/d): PRO with 1.6 g x kg(-1) x d(-1) protein and <170 g/d carbohydrates or CHO with 0.8 g x kg(-1) x d(-1) protein, >220 g/d carbohydrates. At 4 mo, the PRO group had lost 22% more fat mass (FM) (-5.6 +/- 0.4 kg) than the CHO group (-4.6 +/- 0.3 kg) but weight loss did not differ between groups (-8.2 +/- 0.5 kg vs. -7.0 +/- 0.5 kg; P = 0.10). At 12 mo, the PRO group had more participants complete the study (64 vs. 45%, P < 0.05) with greater improvement in body composition; however, weight loss did not differ between groups (-10.4 +/- 1.2 kg vs. -8.4 +/- 0.9 kg; P = 0.18). Using a compliance criterion of participants attaining >10% weight loss, the PRO group had more participants (31 vs. 21%) lose more weight (-16.5 +/- 1.5 vs. -12.3 +/- 0.9 kg; P < 0.01) and FM (-11.7 +/- 1.0 vs. -7.9 +/- 0.7 kg; P < 0.01) than the CHO group. The CHO diet reduced serum cholesterol and LDL cholesterol compared with PRO (P < 0.01) at 4 mo, but the effect did not remain at 12 mo. PRO had sustained favorable effects on serum triacylglycerol (TAG), HDL cholesterol (HDL-C), and TAG:HDL-C compared with CHO at 4 and 12 mo (P < 0.01). The PRO diet was more effective for FM loss and body composition improvement during initial weight loss and long-term maintenance and produced sustained reductions in TAG and increases in HDL-C compared with the CHO diet.

The Relation of Adiposity to Cognitive Control and Scholastic Achievement in Preadolescent Children

Adiposity may be negatively associated with cognitive function in children. However, the findings remain controversial, in part due to the multifaceted nature of cognition and perhaps the lack of accurate assessment of adiposity. The aim of this study was to clarify the relation of weight status to cognition in preadolescent children using a comprehensive assessment of cognitive control, academic achievement, and measures of adiposity. Preadolescent children between 7 and 9 years (n = 126) completed Go and NoGo tasks, as well as the Wide Range Achievement Test 3rd edition (WRAT3), which measures achievement in reading, spelling, and arithmetic. In addition to BMI, fat mass was measured using dual‐energy X‐ray absorptiometry (DXA). Data were analyzed with multiple regression analysis, controlling for confounding variables. Analyses revealed that BMI and fat mass measured via DXA were negatively associated with cognitive control, as children with higher BMI and fat mass exhibited poorer performance on the NoGo task requiring extensive amounts of inhibitory control. By contrast, no relation of weight status to performance was observed for the Go task requiring smaller amounts of cognitive control. Higher BMI and fat mass were also associated with lower academic achievement scores assessed on the WRAT3. These data suggest that adiposity is negatively and selectively associated with cognitive control in preadolescent children. Given that cognitive control has been implicated in academic achievement, the present study provides an empirical basis for the negative relationship between adiposity and scholastic performance.

Muscle Quality, Aerobic Fitness and Fat Mass Predict Lower-Extremity Physical Function in Community-Dwelling Older Adults

Background: Muscle mass, strength and fitness play a role in lower-extremity physical function (LEPF) in older adults; however, the relationships remain inadequately characterized. Objective: This study aimed to examine the relationships between leg mineral free lean mass (MFLMLEG), leg muscle quality (leg strength normalized for MFLMLEG), adiposity, aerobic fitness and LEPF in community-dwelling healthy elderly subjects. Methods: Fifty-five older adults (69.3 ± 5.5 years, 36 females, 19 males) were assessed for leg strength using an isokinetic dynamometer, body composition by dual energy X-ray absorptiometry and aerobic fitness via a treadmill maximal oxygen consumption test. LEPF was assessed using computerized dynamic posturography and stair ascent/descent, a timed up-and-go task and a 7-meter walk with and without an obstacle. Results: Muscle strength, muscle quality and aerobic fitness were similarly correlated with static LEPF tests (r range 0.27–0.40, p < 0.05); however, the strength of the independent predictors was not robust with explained variance ranging from 9 to 16%. Muscle quality was the strongest correlate of all dynamic LEPF tests (r range 0.54–0.65, p < 0.001). Using stepwise linear regression analysis, muscle quality was the strongest independent predictor of dynamic physical function explaining 29–42% of the variance (p < 0.001), whereas aerobic fitness or body fat mass explained 5–6% of the variance (p < 0.05) depending on performance measure. Conclusions: Muscle quality is the most important predictor, and aerobic fitness and fat mass are secondary predictors of LEPF in community-dwelling older adults. These findings support the importance of exercise, especially strength training, for optimal body composition, and maintenance of strength and physical function in older adults.

Is the current BMI obesity classification appropriate for black and white postmenopausal women

Objective:To evaluate the relation between body fatness (%Fat) and body mass index (BMI) and to evaluate the validity of the BMI standards for obesity established by the NIH in older black and white postmenopausal women.Research methods:Height, weight, BMI, and %Fat, assessed by DXA, were determined for 296 healthy, independently living women ranging in age from 50 to 80 years (M±s.d.; 64.4±7.8 years).Results:Per NIH guidelines, 32% were classified as obese (⩾30 kg/m2, mean BMI=28.1±5.5 kg/m2). In contrast, using the %Fat criterion of 38% advocated by Lohman to define obesity, 47% of our sample was obese (mean %Fat=37.3±6.2%). A moderately high curvilinear relation existed between BMI and %Fat (R=0.82, SEE=3.57 %Fat, P<0.05). Race added meaningfully to the prediction of %Fat (P<0.05) such that for the same BMI, black women will have 1% lower body fatness than white women. Based on a %Fat ⩾38 as the criterion for obesity, receiver operating characteristic (ROC) analysis, performed separately by race, indicated that the currently accepted BMI cutpoint for obesity produced low sensitivity (69% and 61% for black and white women, respectively). Alternatively, BMI values⩾28.4 kg/m2 for black women and ⩾26.9 kg/m2 for white women to define obesity maximized classification accuracy.Conclusion:We conclude that current BMI categories may not be appropriate for identifying obesity among postmenopausal women. Furthermore, the relation between BMI and %Fat is different in black compared to white women but remains constant from the sixth through the eighth decade of life.

The Effects of a Higher Protein Intake During Energy Restriction on Changes in Body Composition and Physical Function in Older Women

BACKGROUND The purpose of this double-blind randomized clinical trial was to compare the relative effectiveness of a higher protein and conventional carbohydrate intake during weight loss on body composition and physical function in older women. METHODS Thirty-one overweight or obese, postmenopausal women (mean ± SD: age 65.2 ± 4.6 years, body mass index 33.7 ± 4.9 kg/m(2)) were prescribed a reduced calorie diet (1,400 kcal/day; 15%, 65%, 30% energy from protein, carbohydrate, and fat, respectively) and randomly assigned to 2 × 25 g/day whey protein (PRO n = 15) or maltodextrin (CARB n = 16) supplementation for 6 months. Lean soft tissue (LST) via dual-energy X-ray absorptiometry; thigh muscle, subcutaneous adipose tissue (SAT), and intermuscular adipose tissue with magnetic resonance imaging; knee strength with isokinetic dynamometry; balance and physical function with a battery of performance tests. RESULTS PRO lost more weight than CARB (-8.0% ± 6.2%, -4.1% ± 3.6%, p = .059; respectively). Changes in LST, %LST, and strength, balance, or physical performance measures did not differ between groups (all p > .05). Weight to leg LST ratio improved more in PRO versus CARB (-4.6 ± 3.6%, -1.8 ± 2.6%, p = .03). PRO lost 4.2% more muscle (p = .01), 10.9% more SAT (p = .02), and 8.2% more intermuscular adipose tissue (p = .03) than CARB. Relative to thigh volume changes, PRO gained 5.8% more muscle (p = .049) and lost 3.8% greater SAT (p = .06) than CARB. Weight to leg LST ratio (r(2) = .189, p = .02) and SAT (r(2) = .163, p = .04) predicted improved up and go, relative muscle (r(2) = .238, p = .01) and SAT (r(2) = .165, p = .04) predicted improved transfer test, and %LST predicted improved balance (r(2) = .179, p = .04). CONCLUSIONS A higher protein intake during caloric restriction maintains muscle relative to weight lost, which in turn enhances physical function in older women.

Waist circumference vs body mass index for prediction of disease risk in postmenopausal women.

OBJECTIVE: To test the sensitivity of waist circumference (central adiposity) as an index of disease risk in postmenopausal women.DESIGN: Retrospective analysis of postmenopausal women tested at Washington University School of Medicine.SUSBJECTS: A total of 323 healthy postmenopausal (66±5 y; mean±s.d.) women not using any hormone replacement.MEASUREMENTS: Body composition, hyperinsulinemia (insulin area), triglycerides and HDL-cholesterol.RESULTS: Excess waist size had a stronger association with hyperinsulinemia and hypertriglyceridemia than body mass index (BMI; kg/m2) in otherwise healthy, postmenopausal women. After adjusting for BMI, a strong relation existed between waist circumference and insulin area, HDL-cholesterol and triglycerides (P<0.01). Conversely, after adjusting for waist circumference, no relation was apparent between BMI and the dependent variables of interest. The strength of the association between waist circumference and disease risk became most apparent when analyses were restricted to normal-weight women (BMI 24–28 kg/m2). When BMI was held constant, hyperinsulinemia and triglyceridemia increased dose-dependently with changes in waist size.CONCLUSION: Waist circumference, an easily obtained index of central adiposity, is a more sensitive measure of relative disease risk than is BMI in middle-aged and older women, particularly in normal-weight individuals.

The Negative Association of Childhood Obesity to Cognitive Control of Action Monitoring

The global epidemic of childhood obesity has become a major public health concern. Yet, evidence regarding the association between childhood obesity and cognitive health has remained scarce. This study examined the relationship between obesity and cognitive control using neuroelectric and behavioral measures of action monitoring in preadolescent children. Healthy weight and obese children performed compatible and incompatible stimulus-response conditions of a modified flanker task, while task performance and the error-related negativity (ERN) were assessed. Analyses revealed that obese children exhibited a longer reaction time (RT) relative to healthy weight children for the incompatible condition, whereas no such difference was observed for the compatible condition. Further, obese children had smaller ERN amplitude relative to healthy weight children with lower post-error response accuracy. In addition, healthy weight children maintained post-error response accuracy between the compatible and incompatible conditions with decreased ERN amplitude in the incompatible condition, whereas obese children exhibited lower post-error response accuracy for the incompatible relative to the compatible condition with no change in ERN amplitude between the compatibility conditions. These results suggest that childhood obesity is associated with a decreased ability to modulate the cognitive control network, involving the prefrontal cortex and anterior cingulate cortex, which supports action monitoring.

Exercise and Insulin Resistance in Youth: A Meta-Analysis

BACKGROUND AND OBJECTIVES: The prevalence of obesity and diabetes is increasing among children, adolescents, and adults. Although estimates of the efficacy of exercise training on fasting insulin and insulin resistance have been provided, for adults similar estimates have not been provided for youth. This systematic review and meta-analysis provides a quantitative estimate of the effectiveness of exercise training on fasting insulin and insulin resistance in children and adolescents. METHODS: Potential sources were limited to peer-reviewed articles published before June 25, 2013, and gathered from the PubMed, SPORTDiscus, Physical Education Index, and Web of Science online databases. Analysis was limited to randomized controlled trials by using combinations of the terms adolescent, child, pediatric, youth, exercise training, physical activity, diabetes, insulin, randomized trial, and randomized controlled trial. The authors assessed 546 sources, of which 4.4% (24 studies) were eligible for inclusion. Thirty-two effects were used to estimate the effect of exercise training on fasting insulin, with 15 effects measuring the effect on insulin resistance. Estimated effects were independently calculated by multiple authors, and conflicts were resolved before calculating the overall effect. RESULTS: Based on the cumulative results from these studies, a small to moderate effect was found for exercise training on fasting insulin and improving insulin resistance in youth (Hedges’ d effect size = 0.48 [95% confidence interval: 0.22–0.74], P < .001 and 0.31 [95% confidence interval: 0.06–0.56], P < .05, respectively). CONCLUSIONS: These results support the use of exercise training in the prevention and treatment of type 2 diabetes.

The association of childhood obesity to neuroelectric indices of inhibition

To examine whether childhood obesity is associated with inhibitory control, we compared healthy weight and obese preadolescent childrens task performance along with the N2 and P3 components during a Go/NoGo task. Results indicated that obese children exhibited lower response accuracy relative to healthy weight children during the NoGo task requiring greater amounts of inhibitory control, whereas no such difference was observed during the Go task. Neuroelectric data indicated that healthy weight children exhibited a more frontal distribution for the NoGo P3 relative to the Go P3, whereas obese children had similar topographic distributions between the Go P3 and NoGo P3. Further, obese children had larger NoGo N2 amplitude relative to the Go N2, whereas this difference was not observed for healthy weight children. These findings suggest that childhood obesity is negatively and selectively associated with prefrontal inhibitory control.

Sex impacts the relation between body composition and physical function in older adults.

Objective: To determine the sex-specific relationships between physical activity, aerobic fitness, adiposity (%Fat), mineral-free lean mass (MFLM), and balance and gait performance in older adults. Methods: Eighty-five female and 49 male sedentary, healthy, community-dwelling older adults (mean [SD] age, 69.6 [5.4] and 70.3 [4.7] years, respectively) were evaluated on habitual physical activity via questionnaire, aerobic fitness by a maximal oxygen consumption treadmill test, whole and regional body composition by dual-energy x-ray absorptiometry, and lower extremity physical function using gait tasks and computerized dynamic posturography. Results: As expected, men had less body fat, more lean mass, and higher aerobic fitness than did women and tended to perform better on all lower extremity physical function tasks (all P ≤ 0.1). Physical activity was not related to gait; however, fitness was related to gait in both sexes (r > 0.50, all P < 0.05). Body fat was related to gait in women (r = −0.38, P < 0.05) but not in men. Neither fitness nor body composition was related to balance in men, whereas in women, leg MFLM was positively associated (r = 0.27, P < 0.05). Women, but not men, with a greater ratio of body weight to leg MFLM performed worse on gait tasks (P < 0.001). There was an interaction with sex for %Fat on gait (P = 0.05) and for leg MFLM on balance (P < 0.05). Conclusions: In sedentary healthy older adults, the relation between body composition, aerobic fitness, and balance and gait differs between sexes such that women are more strongly affected by alterations in body composition. Lower %Fat and preservation of lower body lean mass have important implications for reducing the risk of physical disability, especially in older women.