Timothy G. Lohman

Applicability of body composition techniques and constants for children and youths

This review has focused on the chemical immaturity of children and the implications for body composition estimates. Prepubescent and pubescent children deviate considerably in fat-free body composition from the adult reference male, and this has lead investigators to overestimate body fatness in this population using conventional body composition formulas. The use of multicomponent approaches to body composition to obtain more accurate estimates of body fatness in children has provided new information on the body composition of this population. Sex- and age-specific constants, to replace those derived from the reference male, are suggested for further testing and verification as well as for use in the clinical setting. The chemical immaturity in children has its greatest effect on estimating the extent of obesity in children 6 to 11 years of age and in estimating body fatness in the lean, athletic, prepubescent population. Previous estimates of the growth rate of fat and fat-free body are also affected by chemical immaturity. Further research is needed to study the impact of physical activity and inactivity on the composition of the fat-free body during growth, to develop constants for more accurate estimates of fatness in physically active samples of all ages and to validate the constants presented in the less active populations. Future research with multicomponent body composition systems in all populations of children and youth is essential for progress in this area. Results will have an important contribution to the estimation of childhood obesity, prediction of minimal weight in the athletic population and estimates of growth rate of fat and fat-free body mass. The development of body composition methodologies which more accurately measure the growth of muscle and bone as well as fat is a major challenge ahead.

Body fatness and risk for elevated blood pressure, total cholesterol, and serum lipoprotein ratios in children and adolescents.

BACKGROUND Recent studies have shown considerable variation in body fatness among children and adolescents defined as obese by a percentile rank for skinfold thickness. METHODS We examined the relationship between percent body fat and risk for elevated blood pressure, serum total cholesterol, and serum lipoprotein ratios in a biracial sample of 3320 children and adolescents aged 5 to 18 years. Equations developed specifically for children using the sum of subscapular (S) and triceps (T) skinfolds were used to estimate percent fat. The S/T ratio provided an index of trunkal fat patterning. RESULTS Significant overrepresentation (greater than 20%) of the uppermost quintile (UQ) for cardiovascular disease (CVD) risk factors was evident at or above 25% fat in males (32.2% to 37.3% in UQ) and at or above 30% fat in females (26.6% to 45.4% in UQ), even after adjusting for age, race, fasting status, and trunkal fat patterning. CONCLUSIONS These data support the concept of body fatness standards in White and Black children and adolescents as significant predictors of CVD risk factors. Potential applications of these obesity standards include epidemiologic surveys, pediatric health screenings, and youth fitness tests.

A review of psychosocial pre-treatment predictors of weight control.

Prompted by the large heterogeneity of individual results in obesity treatment, many studies have attempted to predict weight outcomes from information collected from participants before they start the programme. Identifying significant predictors of weight loss outcomes is central to improving treatments for obesity, as it could help professionals focus efforts on those most likely to benefit, suggest supplementary or alternative treatments for those less likely to succeed, and help in matching individuals to different treatments. To date, however, research efforts have resulted in weak predictive models with limited practical usefulness. The two primary goals of this article are to review the best individual‐level psychosocial pre‐treatment predictors of short‐ and long‐term (1 year or more) weight loss and to identify research needs and propose directions for further work in this area. Results from original studies published since 1995 show that few previous weight loss attempts and an autonomous, self‐motivated cognitive style are the best prospective predictors of successful weight management. In the more obese samples, higher initial body mass index (BMI) may also be correlated with larger absolute weight losses. Several variables, including binge eating, eating disinhibition and restraint, and depression/mood clearly do not predict treatment outcomes, when assessed before treatment. Importantly, for a considerable number of psychosocial constructs (e.g. eating self‐efficacy, body image, self‐esteem, outcome expectancies, weight‐specific quality of life and several variables related to exercise), evidence is suggestive but inconsistent or too scant for an informed conclusion to be drawn. Results are discussed in the context of past and present conceptual and methodological limitations, and several future research directions are described.

Pretreatment predictors of attrition and successful weight management in women.

OBJECTIVE: This study analyzed baseline behavioral and psychosocial differences between successful and nonsuccessful participants in a behavioral weight management program. Success was defined by commonly used health-related criteria (5% weight loss). Noncompletion was also used as a marker of a failed attempt at weight control.SUBJECTS: A total of 158 healthy overweight and obese women (age, 48.0±4.5 y; BMI, 31.0±3.8 kg/m2; body fat, 44.5±5.3%).INTERVENTION: Subjects participated in a 16-week lifestyle weight loss program consisting of group-based behavior therapy to improve diet and increase physical activity, and were followed for 1 y after treatment.METHODS: At baseline, all women completed a comprehensive behavioral and psychosocial battery assessing dieting/weight history, dietary intake and eating behaviors, exercise, self-efficacy, outcome evaluations, body image, and other variables considered relevant for weight management. Participants who maintained a weight loss of 5% or more at 16 months (or 10% or more of initial fat mass) were classified as successful. Nonsuccessful participants were those who dropped out and completers who had not lost weight at follow-up.RESULTS: Of all participants, 30% (n=47) did not complete initial treatment and/or missed follow-up assessments (noncompleters). Noncompletion was independently associated with more previous weight loss attempts, poorer quality of life, more stringent weight outcome evaluations, and lower reported carbohydrate intake at baseline. In logistic regression, completion status was predicted correctly in 84% of all cases (χ 2=45.5, P<0.001), using baseline information only. Additional predictors of attrition were initial weight, exercise minutes, fiber intake, binge eating, psychological health, and body image. A large variation in weight loss/maintenance results was observed (range: 37.2 kg for 16-month weight change). Independent baseline predictors of success at 16 months were more moderate weight outcome evaluations, lower level of previous dieting, higher exercise self-efficacy, and smaller waist-to-hip ratio. Success status at follow-up was predicted correctly in 74% of all starting cases (χ2=33.6, P<0.001).CONCLUSION: Psychosocial and behavioral variables (eg, dieting history, dietary intake, outcome evaluations, exercise self-efficacy, and quality of life) may be useful as pretreatment predictors of success level and/or attrition in previously overweight and mildly obese women who volunteer for behavioral weight control programs. These factors can be used in developing readiness profiles for weight management, a potentially important tool to address the issue of low success/completion rates in the current management of obesity.

Why bioelectrical impedance analysis should be used for estimating adiposity.

The whole-body bioelectrical impedance analysis (BIA) approach for estimating adiposity and body fat is based on empirical relations established by many investigators. Properly used, this noninvasive body-composition assessment approach can quickly, easily, and relatively inexpensively provide accurate and reliable estimates of fat-free mass (FFM) and total body water (TBW) in healthy populations. The estimated FFM or TBW values are used to calculate absolute and relative body fat amounts. When different investigators follow the same standard BIA procedures and use the same population and criterion method, similar prediction equations and relatively small prediction errors have been reported for measurement of FFM and TBW (SEE: 1.7-3.0 for FFM and 0.23-1.5 kg for TBW). The BIA approach is most appropriate for estimating adiposity of groups in epidemiologic and field studies but has limited accuracy for estimating body composition in individuals. When used as a simple index (stature2/ resistance), BIA is more sensitive and specific for grading average adiposity in groups than some other anthropometric indexes such as the body mass index. Prediction equations based on BIA have been validated and cross-validated in children, youths, adults, and the elderly, in primarily white populations and, to a limited extent, in Asian, black, and Native American populations.

Promoting Physical Activity in Middle School Girls Trial of Activity for Adolescent Girls

BACKGROUND Physical activity is important for weight control and good health; however, activity levels decline in the adolescent years, particularly in girls. DESIGN Group randomized controlled trial. SETTING/PARTICIPANTS Middle school girls with English-speaking skills and no conditions to prevent participation in physical activity in 36 schools in six geographically diverse areas of the United States. Random, cross-sectional samples were drawn within schools: 6th graders in 2003 (n=1721) and 8th graders in 2005 (n=3504) and 2006 (n=3502). INTERVENTION A 2-year study-directed intervention (fall 2003 to spring 2005) targeted schools, community agencies, and girls to increase opportunities, support, and incentives for increased physical activity. Components included programs linking schools and community agencies, physical education, health education, and social marketing. A third-year intervention used school and community personnel to direct intervention activities. MAIN OUTCOME MEASURES The primary outcome, daily MET-weighted minutes of moderate-to-vigorous physical activity (MET-weighted MVPA), was assessed using accelerometry. Percent body fat was assessed using anthropometry. RESULTS After the staff-directed intervention (pre-stated primary outcome), there were no differences (mean= -0.4, 95% CI= -8.2 to 7.4) in adjusted MET-weighted MVPA between 8th-grade girls in schools assigned to intervention or control. Following the Program Champion-directed intervention, girls in intervention schools were more physically active than girls in control schools (mean difference 10.9 MET-weighted minutes of MVPA, 95% CI=0.52-21.2). This difference is about 1.6 minutes of daily MVPA or 80 kcal per week. There were no differences in fitness or percent body fat at either 8th-grade timepoint. CONCLUSION A school-based, community-linked intervention modestly improved physical activity in girls.

The Psychosocial and Behavioral Characteristics Related to Energy Misreporting

Energy underreporting occurs in 2% to 85% and overreporting in 1% to 39% of various populations. Efforts are needed to understand the psychosocial and behavioral characteristics associated with misreporting to help improve the accuracy of dietary self-reporting. Past research suggests that higher social desirability and greater eating restraint are key factors influencing misreporting, while a history of dieting and being overweight are more moderately associated. Eating disinhibition, body image, depression, anxiety, and fear of negative evaluation may be related to energy misreporting, but evidence is insufficient. This review will provide a detailed discussion of the published associations among psychosocial and behavioral characteristics and energy misreporting.

Current status of body composition assessment in sport: review and position statement on behalf of the ad hoc research working group on body composition health and performance, under the auspices of the I.O.C. Medical Commission.

Quantifying human body composition has played an important role in monitoring all athlete performance and training regimens, but especially so in gravitational, weight class and aesthetic sports wherein the tissue composition of the body profoundly affects performance or adjudication. Over the past century, a myriad of techniques and equations have been proposed, but all have some inherent problems, whether in measurement methodology or in the assumptions they make. To date, there is no universally applicable criterion or ‘gold standard’ methodology for body composition assessment. Having considered issues of accuracy, repeatability and utility, the multi-component model might be employed as a performance or selection criterion, provided the selected model accounts for variability in the density of fat-free mass in its computation. However, when profiling change in interventions, single methods whose raw data are surrogates for body composition (with the notable exception of the body mass index) remain useful.

Fat or lean tissue mass: which one is the major determinant of bone mineral mass in healthy postmenopausal women?

The relative importance of fat and lean tissue mass in determining bone mineral mass among postmenopausal women was examined in this 1‐year longitudinal study. Fifty postmenopausal Caucasian women entered the study; 45 of them completed a 1‐year follow‐up. Dual‐energy X‐ray absorptiometry was employed for measuring total and regional bone mineral density (BMD) and bone mineral content (BMC), fat tissue mass (FTM), lean tissue mass (LTM), and body weight. Results from linear regression analysis using the cross‐sectional data (n = 50) of the study indicated that LTM explained a larger percentage of variation in bone mineral mass than did FTM. FTM and LTM were found to be moderately correlated (r = 0.55); when FTM was entered in the same predicting regression models, LTM was a significant predictor (p < 0.05) of the total and regional BMC, but not BMD. The percent FTM (and inversely %LTM) was correlated with BMD and BMC, but significant correlation was primarily found only for total body BMD (or BMC). Weight was the best predictor of total body BMD and BMC. Longitudinally (n = 45), annual changes in both FTM and weight were significantly associated with annual changes in regional BMD after adjustment for initial bone mineral values (p < 0.05). We conclude that bone mineral mass is more closely related to LTM than to FTM, while annual changes in regional BMD are more closely correlated with changes in FTM in healthy postmenopausal women. Meanwhile, increased body weight is significantly associated with increased bone mineral mass.

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 interventions to participants, and (iii) to build a weight loss readiness questionnaire.