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Weight loss resulting from an exercise intervention tends to be lower than predicted. Modest weight loss can arise from an increase in energy intake, physiological reductions in resting energy expenditure, an increase in lean tissue or a decrease in non-exercise activity. Lower than expected, weight loss could also arise from weak and invalidated assumptions within predictive models. To investigate these causes, we systematically reviewed studies that monitored compliance to exercise prescriptions and measured exercise-induced change in body composition. Changed body energy stores were calculated to determine the deficit between total daily energy intake and energy expenditures. This information combined with available measurements was used to critically evaluate explanations for low exercise-induced weight loss. We conclude that the small magnitude of weight loss observed from the majority of evaluated exercise interventions is primarily due to low doses of prescribed exercise energy expenditures compounded by a concomitant increase in caloric intake. [ABSTRACT FROM AUTHOR]

Background/Objectives:In this study, we aimed to validate the accuracy of single-frequency bioelectrical impedance analysis (SF-BIA) at 50 kHz to assess total body water (TBW) against the reference technique deuterium dilution (D2O) and to explore if the simple clinical parameters extracellular fluid (ECF) composition and body shape explain individual differences between D2O and SF-BIA (DiffBIA-D2O).Subjects/Methods:We assessed TBW with D2O and SF-BIA in 26 women and 26 men without known disease or anomalous body shapes. In addition, we measured body shape with anthropometry and ECF composition (osmolality, albumin, glucose, urea, creatinine, sodium and potassium).Results:On group average, SF-BIA to predict TBW agreed well with D2O (SF-BIA, 39.8±10.1 l; D2O, 40.4±10.2 l; and DiffBIA-D2O −0.7 l). In four individuals ('outliers'; 15% of the study population), DiffBIA-D2O was high (−6.8 to +3.8 l). DiffBIA-D2O was associated with individual variations in body shape rather than ECF composition. Using gender-specific analysis, we found that individual variability of waist circumference in men and arm length in women significantly contributed to DiffBIA-D2O. When removing the four 'outliers', these associations were lost.Conclusions:In the majority of our sample, BIA agreed well with D2O. Adjusting for individual variability in body shape by anthropometrical assessment could possibly improve the accuracy of SF-BIA for individuals who deviate from mean values with respect to body shape. However, further studies with higher subject numbers are needed to confirm our findings. [ABSTRACT FROM AUTHOR]

Obesity represents a strong risk factor for developing chronic diseases. Strategies for disease prevention often promote lifestyle changes encouraging participation in physical activity. However, determining what amount of physical activity is necessary for achieving specific health benefits has been hampered by the lack of accurate instruments for monitoring physical activity and the related physiological outcomes. This review aims at presenting recent advances in activity-monitoring technology and their application to support interventions for health promotion. Activity monitors have evolved from step counters and measuring devices of physical activity duration and intensity to more advanced systems providing quantitative and qualitative information on the individuals' activity behavior. Correspondingly, methods to predict activity-related energy expenditure using bodily acceleration and subjects characteristics have advanced from linear regression to innovative algorithms capable of determining physical activity types and the related metabolic costs. These novel techniques can monitor modes of sedentary behavior as well as the engagement in specific activity types that helps to evaluate the effectiveness of lifestyle interventions. In conclusion, advances in activity monitoring have the potential to support the design of response-dependent physical activity recommendations that are needed to generate effective and personalized lifestyle interventions for health promotion. [ABSTRACT FROM AUTHOR]

This study investigated which aspects of the individuals' activity behavior determine the physical activity level (PAL). Habitual physical activity of 20 Dutch adults (age: 26-60 years, body mass index: 24.5±2.7 kg/m2) was measured using a tri-axial accelerometer. Accelerometer output was used to identify the engagement in different types of daily activities with a classification tree algorithm. Activity behavior was described by the daily duration of sleeping, sedentary behavior (lying, sitting, and standing), walking, running, bicycling, and generic standing activities. Simultaneously, the total energy expenditure (TEE) was measured using doubly labeled water. PAL was calculated as TEE divided by sleeping metabolic rate. PAL was significantly associated ( P<0.05) with sedentary time ( R=−0.72), and the duration of walking ( R=0.49), bicycling ( R=0.77), and active standing ( R=0.62). A negative association was observed between sedentary time and the duration of active standing ( R=−0.87; P<0.001). A multiple-linear regression analysis showed that 75% of the variance in PAL could be predicted by the duration of bicycling (Partial R2=59%; P<0.01), walking (Partial R2=9%; P<0.05) and being sedentary (Partial R2=7%; P<0.05). In conclusion, there is objective evidence that sedentary time and activities related to transportation and commuting, such as walking and bicycling, contribute significantly to the average PAL. [ABSTRACT FROM AUTHOR]

Background:Air-displacement plethysmography (ADP) may be a valid and practical technique to assess body composition in a clinical setting.Objective:This study aimed to assess longitudinal changes in body composition using ADP and to compare it with the deuterium dilution technique.Design:The study was a 6-months dietary intervention, consisting of four phases. The first month, subjects were fed in energy balance (phase I). This was followed by 1 month with an energy intake of 33% of energy requirements (phase II), followed by 2 months at 67% of energy requirements (phase III) and 2 months of ad libitum intake (phase IV). Body composition was assessed using ADP (Bod Pod) and deuterium dilution at baseline and at the end of each phase. The baseline analysis included 111 subjects (88 female). Sixty-one subjects (50 female) completed all measurements and were included in the longitudinal analysis.Results:At baseline, the fat mass (FM) as assessed with the Bod Pod was on average 2.3±4.2 kg (mean±2 s.d.) higher than that assessed with deuterium dilution. The difference in FM between techniques increased significantly with increasing FM (R2=0.23; P<0.001). Both techniques showed significant changes in FM over time P<0.001). On average, FM as assessed with the Bod Pod was 2.0 kg higher than with deuterium dilution (P<0.001). During phase II, there was a significant interaction between time and method, meaning that the Bod Pod showed a larger decrease in FM than deuterium dilution.Conclusions:The Bod Pod was able to detect all changes in the body composition, but consistently measured a higher FM than deuterium dilution. [ABSTRACT FROM AUTHOR]