title: The role of free-living daily walking in human weight gain and obesity.
abstract: 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 approximately 2.5 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.
  
  
  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 (approximately 47) short-duration (<15 min), low-velocity ( approximately 1 mph) walking bouts. Lean subjects walked 3.5 miles/day more than obese subjects (n = 10, 10.3 +/- 2.5 vs. n = 12, 6.7 +/- 1.8 miles/day; P = 0.0009). With overfeeding, walking distance decreased by 1.5 miles/day compared with baseline values (-1.5 +/- 1.7 miles/day; P = 0.0005). The decrease in walking that accompanied overfeeding occurred to a similar degree in the lean (-1.4 +/- 1.9 miles/day; P = 0.04) and obese (-1.6 +/- 1.7 miles/day; P = 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.
authors.affiliation: Endocrine Research Unit, Mayo Clinic, Rochester, MN 55905, USA. jim@mayo.edu
authors.forename: James A
authors.initials: JA
authors.lastname: Levine
authors.forename: Shelly K
authors.initials: SK
authors.lastname: McCrady
authors.forename: Lorraine M
authors.initials: LM
authors.lastname: Lanningham-Foster
authors.forename: Paul H
authors.initials: PH
authors.lastname: Kane
authors.forename: Randal C
authors.initials: RC
authors.lastname: Foster
authors.forename: Chinmay U
authors.initials: CU
authors.lastname: Manohar
mesh_terms: D000328:Adult; D001481:Basal Metabolism; D001823:Body Composition; D002149:Energy Intake; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D016138:Walking / Q000502:physiology*; D015430:Weight Gain / Q000502:physiology*