A higher protein intake during caloric restriction maintains muscle relative to weight lost, which in turn enhances physical function in older women.

Study design: Cross-sectional. Objectives: To compare relative body fatness (%Fat) estimates from field methods (skinfold thickness measurement (SKF) and bioelectrical impedance analysis (BIA)) with measures by dual-energy X-ray absorptiometry (DXA). Setting: University of Illinois, Urbana-Champaign, IL, USA. Methods: Field methods used both three-and seven-site SKF prediction equations and BIA generalized, spinal cord injury (SCI)-specific and athlete-specific equations. DXA was used as the reference method. College-aged varsity athletes with SCI (women ¼ 8, men ¼ 8; time since injury 16.2±5.7 years; injury level range T5-L5) were recruited. Results: Mean BMI was 20.8 ± 2.6 and 22.5 ± 2.1 kg m À2 , and mean DXA %Fat was 31.9 ± 3.8 and 20.6±8.4%, for women and men, respectively. All field methods under-predicted the %Fat when compared with DXA (ranges in mean differences: SKF women 2.9-8.2%, SKF men 6.9-12.4%; BIA women 0.5-3.9%, BIA men 0.3-7.0%). None of the field methods accurately predicted the %Fat compared with DXA (total error (TE): SKF women 7.4-12.1%, SKF men 8.4-15.2%; BIA women 5.1-9.3%, BIA men 6.7-10.7%). Of the SKF and BIA prediction equations, Evans et al.'s three-site SKF (r ¼ 0.95, Po0.001, standard error of the estimate (SEE) ¼ 2.8 %Fat) prediction equation provided the best fit for this population. Conclusion: Further studies with larger samples are necessary to develop appropriate prediction equations for field methods in the athletic SCI population.

Limited data on sex differences in body composition changes in response to higher protein diets (PRO) compared to higher carbohydrate diets (CARB) suggest that a PRO diet helps preserve lean mass (LM) in women more so than in men.ObjectiveTo compare male and female body composition responses to weight loss diets differing in macronutrient content.DesignTwelve month randomized clinical trial with 4mo of weight loss and 8mo weight maintenance. SubjectsOverweight (N = 130; 58 male (M), 72 female (F); BMI = 32.5 ± 0.5 kg/m2) middle-aged subjects were randomized to energy-restricted (deficit ~500 kcal/d) diets providing protein at 1.6 g.kg-1.d-1 (PRO) or 0.8 g.kg-1.d-1 (CARB). LM and fat mass (FM) were measured using dual X-ray absorptiometry. Body composition outcomes were tested in a repeated measures ANOVA controlling for sex, diet, time and their two- and three-way interactions at 0, 4, 8 and 12mo.ResultsWhen expressed as percent change from baseline, males and females lost similar amounts of weight at 12mo (M:-11.2 ± 7.1 %, F:-9.9 ± 6.0 %), as did diet groups (PRO:-10.7 ± 6.8 %, CARB:-10.1 ± 6.2 %), with no interaction of gender and diet. A similar pattern emerged for fat mass and lean mass, however percent body fat was significantly influenced by both gender (M:-18.0 ± 12.8 %, F:-7.3 ± 8.1 %, p < 0.05) and diet (PRO:-14.3 ± 11.8 %, CARB:-9.3 ± 11.1 %, p < 0.05), with no gender-diet interaction. Compared to women, men carried an extra 7.0 ± 0.9 % of their total body fat in the trunk (P < 0.01) at baseline, and reduced trunk fat during weight loss more than women (M:-3.0 ± 0.5 %, F:-1.8 ± 0.3 %, p < 0.05). Conversely, women carried 7.2 ± 0.9 % more total body fat in the legs, but loss of total body fat in legs was similar in men and women.ConclusionPRO was more effective in reducing percent body fat vs. CARB over 12mo weight loss and maintenance. Men lost percent total body fat and trunk fat more effectively than women. No interactive effects of protein intake and gender are evident.

Study design: Cross-sectional study comparing athletes with spinal cord injury (SCI) and age and body mass index matched able-bodied controls (AB). Objective: To examine the impact of exercise training on the relation between whole body, regional and intermuscular adipose tissue (IMAT) and glucose tolerance, insulin action and lipid profile. Setting: University Research Laboratory, USA. Methods: Fourteen college-aged athletes with SCI (seven men; duration of injury 16.575.7 years, level of injury T5-L5) and 17 sedentary AB (eight men) were assessed for body composition via dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging. Insulin sensitivity index (ISI) was determined via 2-h oral glucose challenge; standard lipid profile was determined from fasting blood samples. Results: Although ISI was 30% higher in SCI, there were no significant differences between groups in glucose and insulin responses or in lipid measures. Adjusting for absolute and relative thigh IMAT area, fasting insulin (13.875.3 mIU, 16.375.6 mIU; Po0.05; SCI vs AB respectively) and ISI (4.071.4, 3.171.3; Po0.05) were significantly better among SCI athletes compared to AB. Measures of adiposity did not correlate with glucose response or most lipid measures. Within SCI and AB, respectively, ISI correlated strongly (all Po0.05) with absolute (r ¼ À0.70, À0.54) and relative IMAT (r ¼ À0.54, À0.50), than with trunk (r ¼ À0.62, À0.64) and whole body fat mass (r ¼ À0.61, À0.64). Conclusion: Habitual physical activity can maintain insulin sensitivity in SCI compared to sedentary AB controls. Total body fat mass, central adiposity and thigh IMAT appear to impact risk for metabolic disease in SCI individuals with IMAT playing a larger role in SCI than AB.

Dietary protein is theorized to hold both anabolic effects on bone and demineralizing effects mediated by the diet acid load of sulfate derived from methionine and cysteine. The relative importance of these effects is unknown but relevant to osteoporosis prevention. Postmenopausal women (n = 161, 67.9 +/- 6.0 y) were assessed for areal bone mineral density (aBMD) of lumbar spine (LS) and total hip (TH) using dual X-ray absorptiometry, and dietary intakes of protein, sulfur-containing amino acids, and minerals using a USDA multiple-pass 24-h recall. The acidifying influence of the diet was estimated using the ratio of protein:potassium intake, the potential renal acid load (PRAL), and intake of sulfate equivalents from protein. aBMD was regressed onto protein intake then protein was controlled for estimated dietary acid load. A step-down procedure assessed potential confounding influences (weight, age, physical activity, and calcium and vitamin D intakes). Protein alone did not predict LS aBMD (P = 0.81); however, after accounting for a negative effect of sulfate (beta = -0.28; P < 0.01), the direct effect of protein intake was positive (beta = 0.22; P = 0.04). At the TH, protein intake predicted aBMD (beta = 0.18; P = 0.03), but R2 did not improve with adjustment for sulfate (P = 0.83). PRAL and the protein:potassium ratio were not significant predictors of aBMD. Results suggest that protein intake is positively associated with aBMD, but benefit at the LS is offset by a negative impact of the protein sulfur acid load. If validated experimentally, these findings harmonize conflicting theories on the role of dietary protein in bone health.