Obesity occurs when energy intake exceeds energy expenditure. Humans expend energy through purposeful exercise and through changes in posture and movement that are associated with the routines of daily life [called nonexercise activity thermogenesis (NEAT)]. To examine NEAT's role in obesity, we recruited 10 lean and 10 mildly obese sedentary volunteers and measured their body postures and movements every half-second for 10 days. Obese individuals were seated, on average, 2 hours longer per day than lean individuals. Posture allocation did not change when the obese individuals lost weight or when lean individuals gained weight, suggesting that it is biologically determined. If obese individuals adopted the NEAT-enhanced behaviors of their lean counterparts, they might expend an additional 350 calories (kcal) per day.

Objectives-Children and adults spend large portions of their days in front of screens. Our hypothesis was that both children and adults would expend more calories and move more while playing activity-promoting video games compared to sedentary video games.Study Design-In this single-group study, twenty-two healthy children (12 ± 2 years, 11 M, 11 F) and 20 adults (34 ± 11 years, 10 M, 10 F) were recruited. Energy expenditure and physical activity were measured while participants were resting, standing, watching television seated, sitting and playing a traditional sedentary video game, and while playing an activity-promoting video game (Nintendo® Wii™ Boxing). Physical activity was measured using accelerometers and energy expenditure was measured using an indirect calorimeter.Results-Energy expenditure increased significantly above all activities when children or adults played Nintendo® Wii™ (mean increase over resting, 189 ± 63 kcal/hr, p < 0.001, and 148 ± 71 kcal/hr, p < 0.001, respectively). Upon examination of movement using accelerometry, children moved significantly more than adults (55 ± 5 AAU and 23 ± 2 AAU, respectively, p < 0.001) while playing Nintendo® Wii™.Conclusions-Activity-promoting video games have the potential to increase movement and energy expenditure in children and adults.

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Objective To quantify the energy efficiency of locomotion and free-living physical activity energy expenditure of transfemoral amputees using a mechanical and microprocessor-controlled prosthetic knee. Design Repeated-measures design to evaluate comparative functional outcomes. Setting Exercise physiology laboratory and community free-living environment. Participants Subjects (N=15; 12 men, 3 women; age, 42±9y; range, 26 –57y) with transfemoral amputation. Intervention Research participants were long-term users of a mechanical prosthesis (20±10y as an amputee; range, 3–36y). They were fitted with a microprocessor-controlled knee prosthesis and allowed to acclimate (mean time, 18±8wk) before being retested. Main Outcome Measures Objective measurements of energy efficiency and total daily energy expenditure were obtained. The Prosthetic Evaluation Questionnaire was used to gather subjective feedback from the participants. Results Subjects demonstrated significantly increased physical activity–related energy expenditure levels in the participant’s free-living environment (P=.04) after wearing the microprocessor-controlled prosthetic knee joint. There was no significant difference in the energy efficiency of walking (P=.34). When using the microprocessor-controlled knee, the subjects expressed increased satisfaction in their daily lives (P=.02). Conclusions People ambulating with a microprocessor-controlled knee significantly increased their physical activity during daily life, outside the laboratory setting, and expressed an increased quality of life.

OBJECTIVE-Diminished daily physical activity explains, in part, why obesity and diabetes have become worldwide epidemics. In particular, chair use has replaced ambulation, so that obese individuals tend to sit for ϳ2.5 h/day more than lean counterparts. Here, we address the hypotheses that free-living daily walking distance is decreased in obesity compared with lean subjects and that experimental weight gain precipitates decreased daily walking.RESEARCH DESIGN AND METHODS-During weight-maintenance feeding, we measured free-living walking using a validated system that captures locomotion and body movement for 10 days in 22 healthy lean and obese sedentary individuals. These measurements were then repeated after the lean and obese subjects were overfed by 1,000 kcal/day for 8 weeks.RESULTS-We found that free-living walking comprises many (ϳ47) short-duration (Ͻ15 min), low-velocity (ϳ1 mph) walking bouts. Lean subjects walked 3.5 miles/day more than obese subjects (n ϭ 10, 10.3 Ϯ 2.5 vs. n ϭ 12, 6.7 Ϯ 1.8 miles/day; P ϭ 0.0009). With overfeeding, walking distance decreased by 1.5 miles/day compared with baseline values (Ϫ1.5 Ϯ 1.7 miles/day; P ϭ 0.0005). The decrease in walking that accompanied overfeeding occurred to a similar degree in the lean (Ϫ1.4 Ϯ 1.9 miles/day; P ϭ 0.04) and obese (Ϫ1.6 Ϯ 1.7 miles/day; P ϭ 0.008) subjects.CONCLUSIONS-Walking is decreased in obesity and declines with weight gain. This may represent a continuum whereby progressive increases in weight are associated with progressive decreases in walking distance. By identifying walking as pivotal in weight gain and obesity, we hope to add credence to an argument for an ambulatory future. Diabetes 57:548-554, 2008 O besity is epidemic in developed countries and is emerging in middle-and even low-income countries; this in part explains the unprecedented increase in type 2 diabetes worldwide (1). It is widely agreed that this partially reflects mounting sedentariness (2,3). At the beginning of the 20th century 90% of the population of the world was rural. However, over the last century, more than two billion agriculturalists have become city dwellers (4). In the latter transition, physical activity has declined (5). In particular, chair use has replaced ambulation (6) such that obese individuals tend to sit for ϳ2.5 h/day more than lean counterparts (7). Walking is the principal component of nonexercise activity thermogenesis (NEAT), which is the energy expenditure association with free-living daily activities (8,9). This is because people walk for several hours each day and, even at slow velocity, walking doubles energy expenditure (10); hence, the product of the time engaged in walking and its energetic equivalent is numerically substantial. We therefore wondered whether walking might be mechanistically important in weight gain and obesity. To address the hypothesis that free-living daily walking distance is decreased in obesity, we examined the characteristics of free-living walking in lean and obese people. Then, to address the hypothesis t...