A lifetime of change: Measurements of total and basal energy in a large cohort of subjects at ages spanning from before birth to old age document distinct changes that occur during a human lifetime. Pontzer et al . report that energy expenditure (adjusted for weight) in neonates was like that of adults but increased substantially in the first year of life (see the Perspective by Rhoads and Anderson). It then gradually declined until young individuals reached adult characteristics, which were maintained from age 20 to 60 years. Older individuals showed reduced energy expenditure. Tissue metabolism thus appears not to be constant but rather to undergo transitions at critical junctures. —LBR

Background: Diet is a modifiable behavior that influences an individual's health. Because of this, diet assessment is an important component of public health surveillance, evaluating response to community health interventions, and monitoring individual compliance to medical interventions. Diet assessments are usually performed using one of three basic methods: diet recall, diet diaries, or food frequency questionnaires. Although these three assessment instruments have displayed a strong agreement between themselves, when reported intake is compared with intake measured using quantitative nutrient biomarkers, investigators have identified systematic misreporting errors for all three of these self-reported dietary instruments. Aims: This work aims to summarize the state of knowledge regarding misreporting and why it impedes diet–health research and to introduce advances in the collection and the treatment of dietary data. Methods: This work reviews and summarizes published data on misreporting and the recent efforts to reduce such errors. Results: The evidence demonstrates a strong and consistent systematic underreporting of energy intake (EIn) across adults and children studies. Underreporting of EIn has been found to increase with body mass index (BMI), and the differences between macronutrient reports indicate that not all foods are underreported equally. Protein is least underreported, but which specific foods are commonly underreported are not known. Conclusions: Because energy underreporting varies as a function of BMI, self-reported EIn should not be used for the study of energy balance in the study of obesity. The between-individual variability in the underreporting of self-reported intake of energy and other nutrients attenuates diet–disease relationships. Recent efforts to correct for underreporting have reduced misreporting of diet outcomes, but improvements have been incremental in nature and more research is needed to validate and extend these efforts.

Exercise is frequently identified as a predictor of weight maintenance after elective weight loss in retrospective studies of treatments for obesity. We conducted a prospective study to test whether physical activity measured soon after weight loss predicted weight maintenance and to determine how much physical activity was required to optimize maintenance. Thirty-two women [mean (+/- SD) age, 38 +/- 7 y; body mass index (in kg/m2), 24 +/- 3] were recruited through local advertising within 3 mo of reaching their target for weight loss (23 +/- 9 kg). Total energy expenditure (TEE) was measured by the doubly labeled water method. Postabsorptive resting metabolic rate (RMR) and postprandial RMR [expressed as thermic effect of a meal (TEM)] were measured by respiratory gas exchange. Women in the physically active group (ratio of TEE to RMR = 1.89 +/- 0.08) gained 2.5 +/- 3.1 kg during the 12 mo after reaching their target for weight loss, moderately active women (TEE:RMR = 1.64 +/- 0.05) gained 9.9 +/- 10.5 kg, and sedentary women (TEE:RMR = 1.44 +/- 0.08) gained 7.0 +/- 5.9 kg (P < 0.01). Retrospective analyses of weight regain as a function of energy expended in physical activity indicated a threshold for weight maintenance of 47 kJ x kg body wt(-1) x d(-1). This corresponds to an average of 80 min/d of moderate activity or 35 min/d of vigorous activity added to a sedentary lifestyle.

Background: Dual-energy X-ray absorptiometry (DXA) has become one of the most frequently used methods for estimating human body composition. Although the DXA technique has been validated for the measurement of fat-free mass and fat mass, differences in calibration between instruments produced by different manufacturers, as well as between different models produced by the same manufacturer, have been reported. Objective: The objective was to compare the calibration of the QDR 4500A against criterion methods in a large heterogeneous population. Design: DXA-derived body-composition data were obtained from 7 studies: 6 data sets were provided by the investigators, one of which was published. The data included fat mass and fat-free mass measured with a QDR 4500A and criteria measurements of body composition from total body water by dilution at 4 centers, densitometry from 1 center, and four-compartment analysis at 2 centers. Results: In the cohort of 1195 subjects, 602 men and 593 women aged 19–82 y with a body mass index (in kg/m²) of 16–44, the fan-beam DXA overestimated fat-free mass (P < 0.05). A significant difference was observed in all 7 data sets, and the mean (±SE) was 5 ± 1%. Conclusions: It is recommended that the lean soft tissue mass estimate with the fan-beam QDR 4500A be reduced by 5% and that for fat mass be increased by that same mass. This finding is particularly important because the National Health and Nutrition Examination Survey is using the QDR 4500A to assess body composition in a nationally representative sample of persons in the United States.