Physiologic changes after diet combined with structured aerobic exercise or lifestyle activity.

Moderate intensity physical activity achieved through changes in lifestyle may promote weight management. However, little is known about changes in physiologic and metabolic variables when patients lose weight using moderate intensity lifestyle activity instead of traditional structured vigorous aerobic exercise. To compare changes in resting metabolic energy expenditure (REE), fat mass (FM), and fat-free mass (FFM) associated with a 12-week weight loss program combined with either: (1) aerobic exercise (AER); or (2) lifestyle activity (LIFE), we randomized 39 overweight adults (mean body mass index [BMI] = 30.9 +/- 2.8 kg/m(2)) to either diet plus AER (N = 18) or diet plus LIFE (N = 21). Both groups consumed a self-selected diet of 1,200 to 1,800 kcal/d (5,021 to 7,531 kJ/d). The AER group performed vigorous aerobic exercise for up to 45 minutes 3 to 4 d/wk. The LIFE group accumulated 30 minutes of moderate intensity physical activity on most days of the week. Compliance with the respective protocols was monitored on a weekly basis. REE was measured before and after treatment via open-circuit spirometry. The AER group decreased body weight by 8.4% (P<.001)while the LIFE had a reduction of 6.7% (P <.001) after treatment. Over the course of the interventions, the AER and LIFE groups experienced 10.9% (P <.001) and 10.2% (P <.001) reductions in REE, respectively. Aerobic exercise did not prevent reductions in REE to a greater extent than did lifestyle activity in patients consuming a reduced calorie diet. Change in REE was not related to changes in FFM or FM for either group, and there were no differences between groups in reductions of REE, weight, FM, or FFM. A program of diet plus lifestyle physical activity may be a suitable alternative for dieting adults who have difficulty adhering to a program of vigorous activity.