Physical activity and fat-free mass during growth and in later life

Physical activity may be a way to increase and maintain fat-free mass (FFM) in later life, similar to the prevention of fractures by increasing peak bone mass.A study is presented of the association between FFM and physical activity in relation to age.In a cross-sectional study, FFM was analyzed in relation to physical activity in a large participant group as compiled in the International Atomic Energy Agency Doubly Labeled Water database. The database included 2000 participants, age 3–96 y, with measurements of total energy expenditure (TEE) and resting energy expenditure (REE) to allow calculation of physical activity level (PAL = TEE/REE), and calculation of FFM from isotope dilution.PAL was a main determinant of body composition at all ages. Models with age, fat mass (FM), and PAL explained 76\% and 85\% of the variation in FFM in females and males < 18 y old, and 32\% and 47\% of the variation in FFM in females and males ≥ 18 y old, respectively. In participants < 18 y old, mean FM-adjusted FFM was 1.7 kg (95\% CI: 0.1, 3.2 kg) and 3.4 kg (95\% CI: 1.0, 5.6 kg) higher in a very active participant with PAL = 2.0 than in a sedentary participant with PAL = 1.5, for females and males, respectively. At age 18 y, height and FM–adjusted FFM was 3.6 kg (95\% CI: 2.8, 4.4 kg) and 4.4 kg (95\% CI: 3.2, 5.7 kg) higher, and at age 80 y 0.7 kg (95\% CI: −0.2, 1.7 kg) and 1.0 kg (95\% CI: −0.1, 2.1 kg) higher, in a participant with PAL = 2.0 than in a participant with PAL = 1.5, for females and males, respectively.If these associations are causal, they suggest physical activity is a major determinant of body composition as reflected in peak FFM, and that a physically active lifestyle can only partly protect against loss of FFM in aging adults

Total energy expenditure is repeatable in adults but not associated with short-term changes in body composition

Low total energy expenditure (TEE, MJ/d) has been a hypothesized risk factor for weight gain, but repeatability of TEE, a critical variable in longitudinal studies of energy balance, is understudied. We examine repeated doubly labeled water (DLW) measurements of TEE in 348 adults and 47 children from the IAEA DLW Database (mean ± SD time interval: 1.9 ± 2.9 y) to assess repeatability of TEE, and to examine if TEE adjusted for age, sex, fat-free mass, and fat mass is associated with changes in weight or body composition. Here, we report that repeatability of TEE is high for adults, but not children. Bivariate Bayesian mixed models show no among or within-individual correlation between body composition (fat mass or percentage) and unadjusted TEE in adults. For adults aged 20-60 y (N = 267; time interval: 7.4 ± 12.2 weeks), increases in adjusted TEE are associated with weight gain but not with changes in body composition; results are similar for subjects with intervals >4 weeks (N = 53; 29.1 ± 12.8 weeks). This suggests low TEE is not a risk factor for, and high TEE is not protective against, weight or body fat gain over the time intervals tested

Energy compensation and adiposity in humans

Understanding the impacts of activity on energy balance is crucial. Increasing levels of activity may bring diminishing returns in energy expenditure because of compensatory responses in non-activity energy expenditures.1-3 This suggestion has profound implications for both the evolution of metabolism and human health. It implies that a long-term increase in activity does not directly translate into an increase in total energy expenditure (TEE) because other components of TEE may decrease in response-energy compensation. We used the largest dataset compiled on adult TEE and basal energy expenditure (BEE) (n = 1,754) of people living normal lives to find that energy compensation by a typical human averages 28% due to reduced BEE; this suggests that only 72% of the extra calories we burn from additional activity translates into extra calories burned that day. Moreover, the degree of energy compensation varied considerably between people of different body compositions. This association between compensation and adiposity could be due to among-individual differences in compensation: people who compensate more may be more likely to accumulate body fat. Alternatively, the process might occur within individuals: as we get fatter, our body might compensate more strongly for the calories burned during activity, making losing fat progressively more difficult. Determining the causality of the relationship between energy compensation and adiposity will be key to improving public health strategies regarding obesity

Daily energy expenditure through the human life course

Total daily energy expenditure (“total expenditure”) reflects daily energy needs and is a critical variable in human health and physiology, but its trajectory over the life course is poorly studied. We analyzed a large, diverse database of total expenditure measured by the doubly labeled water method for males and females aged 8 days to 95 years. Total expenditure increased with fat-free mass in a power-law manner, with four distinct life stages. Fat-free mass–adjusted expenditure accelerates rapidly in neonates to ~50% above adult values at ~1 year; declines slowly to adult levels by ~20 years; remains stable in adulthood (20 to 60 years), even during pregnancy; then declines in older adults. These changes shed light on human development and aging and should help shape nutrition and health strategies across the life span

Preventing Violence in Seven Countries: Global Convergence in Policies

Do governments take the measures that are supported by the best scientific evidence available? We present a brief review of the situation in: Australia, Canada, Germany, the Netherlands, Spain, the United Kingdom, and the United States. Our findings show surprisingly similar developments across countries. While all seven countries are moving towards evidence-based decision making regarding policies and programs to prevent violence, there remain a number of difficulties before this end can be achieved. For example, there continue to be few randomized controlled trials or rigorous quasi-experimental studies on aggression and violence. Results from experimental research are essential to both policy makers and researchers to determine the effectiveness of programs as well as increase our knowledge of the problem. Additionally, all noted that media attention for violence is high in their country, often leading to management by crisis with the result that policies are not based on evidence, but instead seek to appease public outrage. And perhaps because of attendant organizational problems (i.e., in many countries violence prevention was not under the guise of one particular agency or ministry), most have not developed a coordinated policy focusing on the prevention of violence and physical aggression. It is hypothesized that leaders in democratic countries, who must run for election every 4 to 6 years, may feel a need to focus on short-term planning rather than long-term preventive policies since the costs, but not the benefits for the latter would be incurred while they still served in office. We also noted a general absence of expertise beyond those within scientific circles. The need for these ideas to be more widely accepted will be an essential ingredient to real and sustaining change. This means that there must be better communication and increased understanding between researchers and policy makers. Toward those ends, the recent establishment of the Campbell Collaboration, formed to provide international systematic reviews of program effectiveness, will make these results more available and accessible to politicians, administrators and those charged with making key policy decision

Variation in human water turnover associated with environmental and lifestyle factors

Water is essential for survival, but one in three individuals worldwide (2.2 billion people) lacks access to safe drinking water. Water intake requirements largely reflect water turnover (WT), the water used by the body each day. We investigated the determinants of human WT in 5604 people from the ages of 8 days to 96 years from 23 countries using isotope-tracking (2H) methods. Age, body size, and composition were significantly associated with WT, as were physical activity, athletic status, pregnancy, socioeconomic status, and environmental characteristics (latitude, altitude, air temperature, and humidity). People who lived in countries with a low human development index (HDI) had higher WT than people in high-HDI countries. On the basis of this extensive dataset, we provide equations to predict human WT in relation to anthropometric, economic, and environmental factors.acceptedVersio