Scott B Going

PMID: 10195608;Abstract:

We describe the development, implementation, and use of the process evaluation component of a multisite, primary obesity prevention trial for American Indian schoolchildren. We describe the development and pilot testing of the instruments, provide some examples of the criteria for instrument selection, and provide examples of how process evaluation results were used to document and refine intervention components. The theoretical and applied framework of the process evaluation was based on diffusion theory, social learning theory, and the desire for triangulation of multiple modes of data collection. The primary objectives of the process evaluation were to systematically document the training process, content, and implementation of 4 components of the intervention. The process evaluation was developed and implemented collaboratively so that it met the needs of both the evaluators and those who would be implementing the intervention components. Process evaluation results revealed that observation and structured interviews provided the most informative data; however, these methods were the most expensive and time consuming and required the highest level of skill to undertake. Although the literature is full of idealism regarding the uses of process evaluation for formative and summative purposes, in reality, many persons are sensitive to having their work evaluated in such an in-depth, context-based manner as is described. For this reason, use of structured, quantitative, highly objective tools may be more effective than qualitative methods, which appear to be more dependent on the skills and biases of the researcher and the context in which they are used.

PMID: 8282614;Abstract:

Four methods for predicting body composition were compared in premenopausal females (n = 100), 28-39 yr old, by using underwater weighing (UWW) as the criterion method. The four methods were dual energy X-ray absorptiometry (DEXA), skinfolds, bioelectrical impedance, and body mass index. The sample had a mean percent fat (%fat) of 29.7 ± 6.8% (SD) by DEXA and 29.9 ± 5.8% measured by UWW. DEXA yielded a standard error of estimate (SE) of 2.4% (r = 0.91) for the prediction of %fat from UWW. When %fat was estimated from other methods, larger SEs were obtained: 3.0% for skinfolds, 3.3% for body mass index, and 2.9% for bioelectrical impedance (height²/resistance) plus weight. Individual body density values derived from UWW were corrected for bone mineral variation. DEXA predicted the corrected body density with a lower SE (0.0040 vs. 0.0053 g/ml) than the original density values. We conclude that DEXA was a precise method and correlated highly with fat-free body weight and %fat from UWW in this homogeneous female sample.

PMID: 15687399;Abstract:

Objective: To examine physical activity in second grade American Indian children as a predictor of percentage body fat 3 years later. Research Methods and Procedures: Physical activity was assessed as average vector magnitude (AVM) counts from an accelerometer in 454 second grade children as part of the Pathways study. BMI was assessed, and skinfolds and bioelectrical impedance were used to estimate fat mass, fat-free body mass, and percentage body fat in validated prediction equations. Associations were examined using mixed models regression controlling for baseline body composition. Results: In normal-weight children, higher AVM counts were significantly associated with decreases in percentage body fat. Among overweight children, higher AVM counts were significantly associated with increases in BMI, fat mass, and fat-free mass but not percentage body fat. Discussion: Higher physical activity levels in second grade were associated with lower levels of percentage body fat in fifth grade in normal-weight but not in overweight children. BMI showed no association with physical activity among normal-weight children, and increases in BMI were associated with increasing amounts of physical activity among overweight children. These findings emphasize the importance of valid body composition measures and may indicate important differences in associations between physical activity and adiposity in normal-weight as compared with overweight children. Copyright © 2004 NAASO.

PMID: 16394972;Abstract:

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-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. Copyright © 2006 by the American College of Sports Medicine.