Exercise‐Induced Reduction in Obesity and Insulin Resistance in Women: a Randomized Controlled Trial

Abstract

Objectives: To determine the effects of equivalent diet‐ or exercise‐induced weight loss and exercise without weight loss on subcutaneous fat, visceral fat, and insulin sensitivity in obese women. Research Methods and Procedures: Fifty‐four premenopausal women with abdominal obesity [waist circumference 110.1 ± 5.8 cm (mean ± SD)] (BMI 31.3 ± 2.0 kg/m2) were randomly assigned to one of four groups: diet weight loss (n = 15), exercise weight loss (n = 17), exercise without weight loss (n = 12), and a weight‐stable control group (n = 10). All groups underwent a 14‐week intervention. Results: Body weight decreased by ∼6.5% within both weight loss groups and was unchanged in the exercise without weight loss and control groups. In comparison with controls, cardiorespiratory fitness improved within the exercise groups only (p < 0.01). Reduction in total, abdominal, and abdominal subcutaneous fat within the exercise weight loss group was greater (p < 0.001) than within all other groups. The reduction in total and abdominal fat within the diet weight loss and exercise without weight loss groups was greater than within controls (p < 0.001) but not different from each other (p > 0.05). Visceral fat decreased within all treatment groups (p < 0.008), and these changes were not different from each other. In comparison with the control group, insulin sensitivity improved within the exercise weight loss group alone (p < 0.001). Discussion: Daily exercise without caloric restriction was associated with substantial reductions in total fat, abdominal fat, visceral fat, and insulin resistance in women. Exercise without weight loss was also associated with a substantial reduction in total and abdominal obesity.

Regional differences in abdominal fat loss

“…Further, these results are applicable to postmenopausal women with Abdominal fat loss JA Kanaley et al type 2 diabetes, but we speculate that they are applicable to men and to non-diabetic individuals. In the present study, the women responded with a decrease in abdominal fat with exercise alone (and minimal weight loss) which is similar to earlier findings by Ross et al 14,15 in obese men. As men frequently have more visceral fat than women, it is possible that the pattern of fat loss may be even more disparate in men than women.…”

Is weight loss the optimal target for obesity-related cardiovascular disease risk reduction?

“…These observations underscore the notion that both WC and visceral fat should be primary targets for strategies designed to reduce obesity and related CVD risk. While it is clear that diet-or exercise-induced weight loss is associated with substantial reductions in both WC and visceral fat (14)(15)(16), increasing evidence supports the view that both WC and visceral fat are substantially reduced in response to exercise with minimal or no weight loss (14,15,29).…”

“…Several studies have examined the effect of physical activity on visceral fat independent of weight loss by having study participants consume compensatory kilocalories equivalent to the amount expended during physical activity (12,14,15). The results suggest that in Caucasian lean and obese men and obese women, significant reductions in visceral fat (-10% to -19%) occur consequent to three months of regular physical activity (40 min/day to 60 min/day) despite no significant change in body weight.…”

“…In fact, significant reductions in fat mass, especially visceral fat, often occur concurrent with equal increases in lean body mass in response to physical activity (15). These equal but opposite changes in fat mass and lean mass are not detected by alterations in body weight (15) but may be interpreted from changes in WC.…”

“…Second, acute and chronic exercise is associated with substantial reductions in several cardiometabolic risk factors despite minimal or no change in body weight (11)(12)(13). Third, while WC and visceral fat are reduced consequent to weight loss (14)(15)(16), it is also true that both variables are substantively reduced in response to exercise with minimal or no weight loss (14,15). These observations bring one to question whether weight loss is the optimal outcome for determining the efficacy of treatment strategies designed to reduce obesity and related comorbidities.…”