Percent body fat and chronic disease risk factors in U.S. children and youth.

BACKGROUND: The dramatic increase in pediatric obesity has renewed interest in accurate methods and screening indexes for identifying at-risk children and youth. Whether age-specific standards are needed is a factor that remains uncertain. PURPOSE: This study was designed to describe the age-specific fatness-risk factor relationship in boys and girls across a wide age range. METHODS: Data were from 12,279 white, black, and Mexican-American children and adolescents from the National Health and Nutritional Examination Surveys (NHANES) III (1998-1994) and IV (1999-2004). Children were grouped based on percent fat, estimated from subscapular and triceps skinfolds, and the age-specific relationships between percent fat and chronic disease risk factors (e.g., blood pressure, lipids and lipoprotein levels, glucose, insulin, and circulating C-reactive protein levels) were described in boys and girls, aged 6-18 years. RESULTS: Percent fat was significantly related to risk factor levels. At higher levels of percent fat, the prevalence of adverse cardiovascular disease risk factors was higher, particularly above 20% fat in boys and above 30% fat in girls. In boys and girls, the interaction term age by percent fat was a significant predictor of risk factors, whereas the percent fat by race interaction term was nonsignificant. CONCLUSIONS: The results demonstrate a strong relationship between chronic disease risk factors and percent fat in children and youth that varies by age in boys and girls.

Lifestyle modifies the relationship between body composition and adrenergic receptor genetic polymorphisms, ADRB2, ADRB3 and ADRA2B: a secondary analysis of a randomized controlled trial of physical activity among postmenopausal women.

Genetic variations in the adrenergic receptor (ADR) have been associated with body composition in cross-sectional studies. Recent findings suggest that ADR variants may also modify body composition response to lifestyle. We assessed the role of ADR variants in body composition response to 12 months of resistance training versus control in previously sedentary postmenopausal women. Randomized trial completers were genotyped for A2B (Glu9/12) by fragment length analysis, and B2 (Gln27Glu) and B3 (Trp64Arg) by TaqMan (n = 148, 54% hormone therapy users). Associations between genotypes and body composition, by dual energy X-ray absorptiometry, were analyzed using univariate models. There was no main effect of individual genes on change in body composition, however, gene x exercise interactions were observed for A2B (Glu9/12) and B2 (Gln27Glu) on change in lean soft tissue (LST, p = 0.02); exercisers on the A2B (Glu9-) background gained LST compared to a loss among controls over 12 months (p < 0.05), with no significant intervention effect on the A2B (Glu9+) background. Similarly, there was a significant LST gain with exercise on the B2 (Glu27+) background compared to loss among controls and no intervention effect on the B2 (Glu27-) background. A non-significant association between total body fat (TBF) and B3 (Trp64Arg) persisted among sedentary controls only when intervention groups were separated (%TBF gain with B3 (Arg64+) carriage, p = 0.03); exercisers lost TBF regardless of genotype. In summary, effect modification by lifestyle was demonstrated on ADRA2B, B2, and B3 genetic backgrounds. Individuals with certain ADR genotypes may be more vulnerable to adverse changes in body composition with sedentary behavior, thus these candidate genes warrant further study.

Progressive resistance training improves overall physical activity levels in patients with early osteoarthritis of the knee: a randomized controlled trial.

BACKGROUND: Prescription of resistance training (RT) exercises is an essential aspect of management for knee osteoarthritis (OA). However, whether patients with knee OA who are randomly assigned to receive RT simply substitute RT for other modes of physical activity remains unclear. OBJECTIVE: The aim of this study was to determine the effect of a structured RT intervention on overall levels of moderate- and vigorous-intensity physical activity (MVPA) in patients with early-onset knee OA. The study compared patients with early-onset OA who participated in an RT program, those who participated in a self-management (SM) program, and those who participated in both RT and SM. Because participants randomly assigned to receive the RT intervention may simply switch activity modes, resulting in little net effect, we assessed total MVPA in addition to tracking changes in strength (force-generating capacity). DESIGN AND INTERVENTION: This study was a randomized controlled trial comparing the effectiveness of SM alone, RT alone, and combined RT+SM on MVPA in patients with early OA of the knee. SETTING: The study was conducted on a university campus, with patient recruitment from the local community. PARTICIPANTS: The participants in this study were 171 patients (74% women, 26% men) with knee OA. They had a mean age of 55.1 (SD=7.1) years, a mean body mass index of 27.6 (SD=4.2) kg/m(2), and radiographic status of grade II OA (and no higher) in at least one knee, as defined by the Kellgren and Lawrence classification. They wore an accelerometer while awake (X=14.2 [SD=2.2] hours) for 5 to 7 contiguous days (X=6.8 [SD=0.5] days) at baseline and at 3 and 9 months of intervention. RESULTS: The participants engaged in MVPA a mean of 26.2 (SD=19.3) minutes per day at baseline. Both groups significantly increased their MVPA from baseline to 3 months (RT group by 18% [effect size (d)=0.26]; SM group by 22% [effect size (d)=0.25]), but only the RT group sustained those changes at 9 months (RT group maintained a 10% increase [effect size (d)=0.15]; SM group maintained a 2% increase [effect size (d)=0.03]). A significant group x time interaction for MVPA indicated that the RT group maintained higher MVPA levels than the SM group. LIMITATIONS: Lack of direct measures of energy expenditure and physical function was a limitation of the study. CONCLUSIONS: Patients with early-onset OA of the knee can engage in an RT program without sacrificing their overall MVPA levels. These results support the value of RT for management of knee OA.

Resistance training predicts 6-yr body composition change in postmenopausal women.

PURPOSE: The aim of this study was to examine the association of exercise frequency (ExFreq) and volume (total weight lifted by military press and squats (SQ)) with change in body composition among postmenopausal women participating in a progressive resistance training study. METHODS: Previously, sedentary women (n = 122, age = 56.3 +/- 4.3 yr) were followed for 6 yr. At 6 yr, there were women who had been randomly assigned to resistance training at baseline (n = 65) controls that were permitted to cross over to the exercise program at 1 yr (n = 32) and 25 true controls. Exercisers and crossovers directed to perform eight core exercises for two sets of eight repetitions at 70%-80% of one-repetition maximum, three times weekly, plus progressive weight bearing, stretching, and balance. Body weight and fat were measured at baseline and annually using anthropometry and dual-energy x-ray absorptiometry. RESULTS: Average change in body weight and total body fat were 0.83 +/- 5.39 and 0.64 +/- 4.95 kg at 6 yr, respectively. In multiple linear regression, ExFreq, military press, and SQ were significantly inversely associated with change in body weight (standardized beta coefficient (SBC) = -0.22 to -0.28, P < 0.01), fat (SBC = -0.25 to -0.33, P < 0.01), and trunk fat (SBC = -0.20 to -0.31, P < 0.03) after adjusting for age, years on hormone therapy, change in lean soft tissue, baseline body composition, and baseline habitual exercise. The lowest tertile of SQ (equivalent to 2.5% attendance) demonstrated significant gain in weight, fat, and trunk fat over 6 yr (P < 0.004), whereas the highest tertile SQ (equivalent to 64% attendance) was able to maintain their weight, total, and regional fat. CONCLUSIONS: We conclude that resistance training is a viable long-term method to prevent weight gain and deleterious changes in body composition in postmenopausal women.

Maintenance of weight loss in overweight middle-aged women through the Internet.

OBJECTIVE: The purpose of this study was to compare weight regain in a group of perimenopausal women (48.0+/-4.4 years old), randomized to a 12-month weight maintenance Internet intervention or to self-directed weight maintenance after a 4-month weight loss treatment. METHODS AND PROCEDURES: After a 4-month behavioral weight loss program, 135 women were randomized to either Internet or self-directed groups. The Internet group (n=66) used a website to gain information and complete logs concerning their weight, diet, and exercise progress over a 12-month follow-up. The 69 self-directed women had no contact with study staff. All women were measured for weight and body composition, and diet intake, and were interviewed using the 7-day physical activity questionnaires at baseline, 4 months, and 16 months. RESULTS: At the end of the 12-month follow-up, the Internet and self-directed groups had regained on average 0.4+/-5.0 kg and 0.6+/-4.0 kg, respectively (P=0.5). In within-group analyses, Internet diet-log entries were correlated with follow-up weight change (r=-0.29; P<0.05) and moderately with change in exercise energy expenditure (EEE; r=0.44; P<0.01). Follow-up weight change was not correlated with change in dietary intake. DISCUSSION: While significant weight loss was maintained over follow-up by both groups of women, Internet use did not surpass self-direction in helping to sustain weight loss. Among Internet users, Internet use was related to weight change and EEE.

Plasma and dietary carotenoids are associated with reduced oxidative stress in women previously treated for breast cancer.

Dietary carotenoids show numerous biological activities, including antioxidant activity, induction of apoptosis, and inhibition of mammary cell proliferation. Studies examining the role of carotenoid consumption in relation to breast cancer recurrence are limited and report mixed results. We tested the hypothesis that breast cancer survivors with high dietary and plasma carotenoids would show significantly lower levels of oxidative stress than breast cancer survivors with low dietary and plasma carotenoid levels. Two hundred seven postmenopausal breast cancer survivors from the Women's Healthy Eating and Living Study volunteered for this ancillary study. Dietary data were analyzed by the Arizona Food Frequency Questionnaire and plasma carotenoids alpha-carotene, beta-carotene, lutein plus zeaxanthin, lycopene, and beta-cryptoxanthin and quantified with high-performance liquid chromatography, and immunoaffinity chromatography-monoclonal antibody-based ELISAs were used to analyze the urine samples for 8-hydroxy-2'-deoxyguanosine (8-OhdG) and 8-iso-prostaglandin-F2alpha (8-iso-PGF2alpha). The correlations between dietary and plasma carotenoids were 0.34 for beta-carotene, 0.46 for alpha-carotene, 0.39 for beta-cryptoxanthin, 0.27 for lycopene, 0.30 for lutein plus zeaxanthin, and 0.30 for total carotenoids. The 8-OHdG oxidative stress biomarker was significantly reduced at the highest quartile of total plasma carotenoid concentrations (P = 0.001) and 8-iso-PGF2alpha was moderately reduced (P = 0.088). Dietary carotenoid levels were not significantly associated with oxidative, stress indicators, although dietary lycopene and lutein/zeaxanthin were modestly associated with 8-OHdG levels (P = 0.054 and 0.088, respectively). Key findings include a significant inverse association between total plasma carotenoid concentrations and oxidative stress as measured by urinary 8-OHdG and a moderately significant inverse association with 8-iso-PGF2alpha, a protective association that was not shown for dietary carotenoid intake.

Cruciferous vegetable intake questionnaire improves cruciferous vegetable intake estimates.

OBJECTIVE: To develop a validated, focused Cruciferous Vegetable Food Frequency Questionnaire (FFQ) as an assessment tool for specific quantification of dietary cruciferous vegetable exposure. DESIGN/METHODS: Participants (n=107; 18 to 76 years old) completed a standard FFQ and the Cruciferous Vegetable FFQ twice over a 2-week period. Repeat dietary recalls were collected on 3 days over the same 2-week period. Urinary dithiocarbamate was determined as a biomarker of cruciferous vegetable intake. STATISTICAL ANALYSES: Descriptive statistics of intake; paired t tests and sign tests for comparison of intake estimates between instruments; Spearman correlations to assess reliability and associations between diet instruments and urinary dithiocarbamate. RESULTS: Cruciferous vegetable intake was significantly correlated between the two FFQs (r(s)=0.58), although the Cruciferous Vegetable FFQ estimated intake 35 g higher than the standard FFQ. The Cruciferous Vegetable FFQ was reliable, with a repeated measures correlation of 0.69 (P

Exercise motivation, eating, and body image variables as predictors of weight control.

PURPOSE: This study investigated changes in psychosocial variables related to exercise, eating, and body image during a weight reduction program and evaluated their association with weight loss in middle-aged overweight and obese women up to 1 yr after intervention. METHODS: The 136 participants (age, 48.1 +/- 4.4 yr; weight, 30.6 +/- 5.6 kg x m(-2)) who completed the 4-month lifestyle weight reduction program (86% retention), losing -6.2 +/- 4.6% (P < 0.001) of their initial weight, were followed up for 12 additional months. Of these, 82% completed 16-month assessments (weight change, -5.5 +/- 7.7%, P < 0.001). Psychosocial variables were assessed by validated instruments in standardized conditions at baseline and after the intervention (4 months). RESULTS: Compared with 4-month assessments, body weight did not change at 16 months (P > 0.09). Changes in eating restraint, disinhibition, and hunger; exercise, self-efficacy, and intrinsic motivation; body shape concerns; and physical self-worth were associated with weight change at 4 months (P < 0.001, except hunger, P < 0.05). Baseline-adjusted 4-month scores in all psychosocial variables also predicted weight change from baseline to 16 months (P < 0.01), except hunger (P > 0.05). After controlling for 4-month weight change and other covariates, increases in exercise intrinsic motivation remained predictive of weight loss at 16 months (P < 0.05). Multiple linear regression showed that eating variables were significant and independent correlates of short-term weight change, whereas changes in exercise variables were stronger predictors of longer term weight outcomes. CONCLUSIONS: Results highlight the importance of cognitive processes during weight control and support the notion that initial focus on diet is associated with short-term weight loss, while change in exercise-related motivational factors, with a special emphasis on intrinsic sources of motivation (e.g., interest and enjoyment in exercise), play a more important role in longer term weight management.

Exercise frequency and calcium intake predict 4-year bone changes in postmenopausal women.

The aim of this study was to examine the association of exercise frequency and calcium intake (CI) with change in regional and total bone mineral density (BMD) in a group of postmenopausal women completing 4 years of progressive strength training. One hundred sixty-seven calcium-supplemented (800 mg/day) sedentary women (56.1+/-4.5 years) randomized to a progressive strength training exercise program or to control were followed for 4 years. Fifty-four percent of the women were using hormone therapy (HT) at baseline. At 1 year, controls were permitted to begin the exercise program (crossovers). The final sample included 23 controls, 55 crossovers, and 89 randomized exercisers. Exercisers were instructed to complete two sets of six to eight repetitions of exercises at 70-80% of one repetition maximum, three times weekly. BMD was measured at baseline and thereafter annually using dual-energy X-ray absorptiometry. Four-year percentage exercise frequency (ExFreq) averaged 26.8%+/-20.1% for crossovers (including the first year at 0%), and 50.4%+/-26.7% for exercisers. Four-year total CI averaged 1,635+/-367 mg/day and supplemental calcium intake, 711+/-174 mg/day. In adjusted multiple linear regression models, ExFreq was positively and significantly related to changes in femur trochanter (FT) and neck (FN), lumbar spine (LS), and total body (TB) BMD. Among HT users, FT BMD increased 1.5%, and FN and LS BMD, 1.2% (p<0.01) for each standard deviation (SD) of percentage ExFreq (29.5% or 0.9 days/week). HT non-users gained 1.9% and 2.3% BMD at FT and FN, respectively, (p<0.05) for every SD of CI. The significant, positive, association between BMD change and ExFreq supports the long-term usefulness of strength training exercise for the prevention of osteoporosis in postmenopausal women, especially HT users. The positive relationship of CI to change in BMD among postmenopausal women not using HT has clinical implications in light of recent evidence of an increased health risk associated with HT.

Resistance training in postmenopausal women with and without hormone therapy.

PURPOSE: The main purpose of this study was to analyze the impact of a 1-yr resistance-training program on body composition and muscle strength in postmenopausal women, and to describe the impact of hormone replacement therapy (HRT) on body composition changes, with and without exercise. Secondarily, we wanted to study dose-response relationships between measures of program compliance and changes in primary outcomes. METHODS: Subjects were postmenopausal women (40-66 yr) randomly assigned to an exercise (EX) group (N = 117) and a nonexercise group (N = 116). The EX group participated in a 1 yr trainer-supervised resistance-training program, 60-75 min.d-1, 3 d.wk-1. Lean soft tissue (LST) and fat tissue (FT) changes were measured by dual-energy x-ray absorptiometry and strength by one-repetition maximum testing. RESULTS: Significant (P < 0.001) gains in LST were observed for women who exercised, regardless of HRT status, whereas women who did not exercise lost LST (P < 0.05) if they were not taking HRT, and gained LST (P = 0.08) if they were on HRT. The only significant FT losses were observed for women who exercised while on HRT (P < 0.05). Strength increases were observed at all sites (P < 0.001). Total weight lifted by subjects in their training sessions was a significant predictor of changes in LST (P < 0.001) and strength (P < 0.01). CONCLUSIONS: Resistance and weight-bearing exercise significantly changed total and regional body composition in postmenopausal women by increasing LST in all women and decreasing FT in women on HRT. Hormone therapy showed no independent effects on body composition, but it protected nonexercising women from losses in LST. The lean and muscle strength changes observed were partially dependent on the volume of training, as expressed by attendance and total weight lifted in 1 yr of training.

Weight lifted in strength training predicts bone change in postmenopausal women.

PURPOSE: The aim of this study was to examine the relationship between weight lifted in 1 yr of progressive strength training and change in bone mineral density (BMD) in a group of calcium-replete, postmenopausal women. METHODS: As part of a large clinical trial, 140 calcium-supplemented women, 44-66 yr old, were randomized to a 1-yr progressive strength-training program. Half of the women were using hormone replacement therapy. Three times weekly, subjects completed two sets of six to eight repetitions in eight core exercises at 70-80% of one repetition maximum. BMD was measured at baseline and 1 yr. RESULTS: In multiple linear regression, the increase in femur trochanter (FT) BMD was positively related to total weight lifted (0.001 g.cm (-2)) for a SD of weight lifted, P< 0.01) after adjusting for age, baseline factors, HRT status, weight change, cohort, and fitness center. The weighted squats showed the strongest (0.002 g.cm(-2)) for a SD of weight lifted, P< 0.001), whereas the back extension exhibited the weakest (0.0005 g.cm(-2)) for a SD of weight lifted, P< 0.26) association with change in FT BMD. The amount of weight lifted in the weighted march exercise was significantly related to total body BMD (0.0006 g.cm(-2)) for a SD of weight lifted, P< 0.01). The associations between weight lifted and BMD for the femur neck or lumbar spine were not significant. CONCLUSION: Evidence of a linear relationship between BMD change and total and exercise-specific weight lifted in a 1-yr strength-training program reinforces the positive association between this type of exercise and BMD in postmenopausal women.

Weight loss readiness in middle-aged women: psychosocial predictors of success for behavioral weight reduction.

Accurate prediction of weight loss success and failure has eluded researchers for many years. Thus, we administered a comprehensive psychometric battery before a 4-month lifestyle behavioral weight reduction program and analyzed weight changes during that period to identify baseline characteristics of successful and unsuccessful participants, among 112 overweight and obese middle-aged women (age, 47.8 +/- 4.4 years; BMI, 31.4 +/- 3.9 kg/m2). Mean weight and percentage fat losses among the 89 completers were -5.4 kg and -3.4%, respectively (p < .001). A higher number of recent dieting attempts and recent weight loss, more stringent weight outcome evaluations, a higher perceived negative impact of weight on quality of life, lower self-motivation, higher body size dissatisfaction, and lower self-esteem were associated with less weight loss and significantly distinguished responders from nonresponders among all participants. These findings are discussed as to their usefulness (i) to screen individuals before treatment, (ii) to provide a better match between interventions to participants, and (iii) to build a weight loss readiness questionnaire.