A Worksite Program for Overweight Middle-Aged Men Achieves Lesser Weight Loss With Exercise Than With Dietary Change

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Abstract

Objective To compare changes in total and regional body composition using dual energy X-ray absorptiometry (DEXA) after subjects lost weight through change in diet or exercise.

Design A 12-month, randomized, controlled study of two weight-loss interventions — low-fat diet ad libitum or moderate, unsupervised exercise — in free-living, middle-aged men. Compliance was determined at monthly measurement sessions through food records and activity logs; DEXA scans were performed every 3 months.

Subjects/setting Fifty-eight overweight men (mean body mass index=29.0±2.6; mean age=43.4±5.7 years) recruited from a national corporation were assigned randomly to diet, exercise, or control groups.

Interventions One group reduced dietary fat to 26.4% of energy intake but kept activity unchanged; another group self-selected aerobic exercise (three sessions per week at 65% to 75% maximum heart rate) but kept diet unchanged. A control group maintained weight.

Main outcome measures At 12 months, measurements of weight, total and regional fat mass and lean mass, energy intake, and percentage dietary fat; physical activity indexes. Statistical analyses Results were analyzed using paired t tests and analysis of variance.

Results Mean weight loss was 6.4±3.3 kg in dieters and 2.6+3.0 kg in exercisers; control subjects maintained weight. DEXA scans revealed that 40% of dieters’ weight loss was lean tissue; more than 80% of weight lost by exercisers was fat. Exercisers maintained limb lean tissue and lost fat mass.

Conclusions Greater total weight and lean tissue loss occurred when subjects lost weight through a low-fat diet consumed ad libitum than when subjects participated in unsupervised aerobic exercise. Use of DEXA enabled identification of progressive total and regional changes in fat and lean tissue. J Am Diet Assoc. 1997; 97:37–42.

Section snippets

Methods

Sixty-six overweight but otherwise healthy men were recruited from a national business corporation and fully informed of the protocol of the 12-month prospective worksite study. After completion of a satisfactory cardiovascular fitness test, each subject was assigned randomly to a program of weight loss through diet, weight loss through exercise, or weight maintenance. Fifty-eight of the subjects completed 12 months of the study (18 in the diet group, 21 in the exercise group, 19 in the control

Results

No significant differences in personal and anthropometric characteristics were noted between groups at baseline (Table 1). There were no differences between groups in total dietary energy intake nor in percentage of energy from carbohydrate, protein, and fat at baseline. At 12 months, the diet group was significantly different from baseline and from the exercise and control groups in intake of total energy and energy from fat, which fell to 26.4% (Table 2).

The mean activity levels were similar

Discussion

The study was undertaken in a workplace situation with free-living subjects who consumed low-fat diets ad libitum or participated in unsupervised exercise interventions appropriate for promotion of weight control (28), (29). Distinctive features of the study included its randomized, controlled design, its high retention of subjects, and its use of DEXA.

The conservation of lean tissue in subjects after an exercise-induced weight-loss program is consistent with previous studies. Exercisers in the

Applications

A low-fat diet consumed ad libitum without change in exercise habits can achieve significant weight loss, but the composition of the loss consists of a high proportion of lean tissue. Alternatively, moderate, self-directed, unsupervised aerobic exercise without dietary change achieves a greater proportion of fat loss within a smaller absolute weight loss. Increased exercise alone encourages greater fat loss, whereas diet without exercise results in greater lean tissue loss and overall weight

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