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Reduction in Obesity and Related Comorbid Conditions after Diet-Induced Weight Loss or Exercise-Induced Weight Loss in Men: A Randomized, Controlled Trial

Robert Ross, PhD; Damon Dagnone, MSc; Peter J.H. Jones, PhD; Heidi Smith, BSc, RD; Anne Paddags, MSc; Robert Hudson, MD, PhD; and Ian Janssen, MSc
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Copyright ©2004 by the American College of Physicians

Ann Intern Med. 2000;133(2):92-103. doi:10.7326/0003-4819-133-2-200007180-00008
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Background: The independent effects of diet- or exercise-induced weight loss on the reduction of obesity and related comorbid conditions are not known. The effects of exercise without weight loss on fat distribution and other risk factors are also unclear.

Objective: To determine the effects of equivalent diet- or exercise-induced weight loss and exercise without weight loss on subcutaneous fat, visceral fat, skeletal muscle mass, and insulin sensitivity in obese men.

Design: Randomized, controlled trial.

Setting: University research center.

Participants: 52 obese men (mean body mass index [±SD], 31.3 ± 2.0 kg/m2) with a mean waist circumference of 110.1 ± 5.8 cm.

Intervention: Participants were randomly assigned to one of four study groups (diet-induced weight loss, exercise-induced weight loss, exercise without weight loss, and control) and were observed for 3 months.

Measurements: Change in total, subcutaneous, and visceral fat; skeletal muscle mass; cardiovascular fitness; glucose tolerance and insulin sensitivity.

Results: Body weight decreased by 7.5 kg (8%) in both weight loss groups and did not change in the exercise without weight loss and control groups. Compared with controls, cardiovascular fitness (peak oxygen uptake) in the exercise groups improved by approximately 16% (P < 0.01). Although total fat decreased in both weight loss groups (P < 0.001), the average reduction was 1.3 kg (95% CI, 0.3 to 2.3 kg) greater in the exercise-induced weight loss group than in the diet-induced weight loss group (P = 0.03). Similar reductions in abdominal subcutaneous, visceral, and visceral fat–to–subcutaneous fat ratios were observed in the weight loss groups (P < 0.001). Abdominal and visceral fat also decreased in the exercise without weight loss group (P = 0.001). Plasma glucose and insulin values (fasting and oral glucose challenge) did not change in the treatment groups compared with controls (P = 0.10 for all comparisons). Average improvement in glucose disposal was similar in the diet-induced weight loss group (5.6 mg/kg skeletal muscle per minute) and in the exercise-induced weight loss group (7.2 mg/kg skeletal muscle per minute) (P > 0.2). However, these values were significantly greater than those in the control and exercise without weight loss groups (P < 0.001).

Conclusions: Weight loss induced by increased daily physical activity without caloric restriction substantially reduces obesity (particularly abdominal obesity) and insulin resistance in men. Exercise without weight loss reduces abdominal fat and prevents further weight gain.


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Figure 1.
Flow of participants through the study.

OGTT = oral glucose tolerance test.

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Figure 2.
Reduction in whole-body subcutaneous fat (white bars) and visceral fat (striped bars) after a 3-month treatment period.

The asterisks indicate a greater within-treatment reduction in subcutaneous fat than in visceral fat compared with the control group ( < 0.01). The daggers indicate a greater within-group relative reduction in visceral fat than in subcutaneous compared with the control group ( < 0.01). Data are expressed as the mean + SE of measurement. C = control group; DWL = diet-induced weight loss group; EWL = exercise-induced weight loss group; EWW = exercise without weight loss group.

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