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.

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.

. Abdominal adiposity and insulin resistance in obese men. Am J Physiol Endocrinol Metab 282: E657-E663, 2002; 10.1152/ajpendo.00469.2001.-We examined the independent relationships among various visceral and abdominal subcutaneous adipose tissue (AT) depots, glucose tolerance, and insulin sensitivity in 89 obese men. Measurements included an oral glucose tolerance test (OGTT), glucose disposal by euglycemic clamp, and abdominal and nonabdominal (e.g., peripheral) AT by magnetic resonance imaging (MRI). OGTT glucose and glucose disposal rates were related (P Ͻ 0.05) to visceral AT (r ϭ 0.50 and Ϫ0.41, respectively). These observations remained significant (P Ͻ 0.05) after control for nonabdominal and abdominal subcutaneous AT, and maximal O 2 consumption (V O2 max). Abdominal subcutaneous AT was not a significant correlate (P Ͼ 0.05) of any metabolic variable after control for nonabdominal and visceral AT and V O2 max. Division of abdominal subcutaneous AT into deep and superficial depots and visceral AT into intra-and extraperitoneal AT depots did not alter the observed relationships. Further analysis matched two groups of men for abdominal subcutaneous AT but also for low and high visceral AT. Men with high visceral AT had higher OGTT glucose values and lower glucose disposal rates compared with those with low visceral AT values (P Ͻ 0.05). A similar analysis performed on two groups of men matched for visceral AT but also for high and low abdominal subcutaneous AT revealed no statistically different values for any metabolic variable (P Ͼ 0.10). In conclusion, visceral AT alone is a strong correlate of insulin resistance independent of nonabdominal and abdominal subcutaneous AT and cardiovascular fitness. Subdivision of visceral and abdominal subcutaneous AT by MRI did not provide additional insight into the relationship between abdominal obesity and metabolic risk in obese men. subcutaneous adipose tissue; insulin sensitivity; visceral adipose tissue DEBATE CONTINUES regarding the independent contribution of abdominal subcutaneous and visceral adipose tissue (AT) toward the etiology of insulin resistance. Whereas some researchers report that visceral AT is the stronger correlate (11,13,15,32), others find that abdominal subcutaneous AT is largely responsible for the established association between abdominal obesity and insulin resistance (1, 2, 19). It has recently been suggested that the discrepancies may be resolved by subdividing abdominal subcutaneous AT according to differences in metabolic characteristics (20,26,38,40). Abdominal subcutaneous AT can be subdivided into superficial and deep compartments by use of the fascia superficialis. The rationale for this division presumes that adipocytes within the deep compartment are more metabolically active compared with superficial adipocytes (12,25). On the assumption that the liberation of nonesterified fatty acids adversely effects insulin action (29, 37), it follows that the deep compartment would be the stronger predictor of insulin resistance. Indeed, Kell...

It is unclear whether chronic exercise without caloric restriction or weight loss is a useful strategy for obesity reduction in obese men with and without Type 2 diabetes (T2D). We examined the effects of exercise without weight loss on total and regional adiposity and skeletal muscle mass and composition in lean men and in obese men with and without T2D. Twenty-four men participated in 13 wk of supervised aerobic exercise, five times per week for 60 min at a moderate intensity (approximately 60% peak oxygen uptake). Total and regional body composition was measured by magnetic resonance imaging. Skeletal muscle composition was determined using computed tomography. Cardiorespiratory fitness was assessed using a graded maximal treadmill test. Body weight did not change within any group in response to exercise (P > 0.1). Significant reductions in total, abdominal subcutaneous, and visceral fat were observed within each group (P < 0.01). The reduction in total and abdominal subcutaneous fat was not different (P > 0.1) between groups; however, the reduction in visceral fat was greater (P < 0.01) in the obese and T2D groups by comparison to the lean group. A significant (P < 0.01) increase in total skeletal muscle, high-density muscle area, and mean muscle attenuation was observed independent of group, and these changes were not different between groups (P > 0.1). Accordingly, whole body fat-to-muscle ratio was increased (P < 0.01) independent of groups. In conclusion, regular exercise without weight loss is associated with a substantial reduction in total and visceral fat and in skeletal muscle lipid in both obesity and T2D.

The independent relationships between visceral and abdominal sc adipose tissue (AT) depots, muscle composition, and insulin sensitivity were examined in 40 abdominally obese, premenopausal women. Measurements included glucose disposal by euglycemic clamp, muscle composition by computed tomography, abdominal and nonabdominal (e.g. leg) AT by magnetic resonance imaging and cardiovascular fitness. Glucose disposal rates were negatively related to visceral AT mass (r = -0.42, P < 0.01). These observations remained significant (P < 0.01) after control for nonabdominal and abdominal sc AT, muscle attenuation, and peak oxygen uptake. Total, abdominal, or leg sc AT or muscle attenuation was not significantly (P > 0.10) related to glucose disposal. Subdivision of abdominal sc AT into anterior and posterior depots did not alter the observed relationships. Further analysis matched two groups of women for abdominal sc AT but with low and high visceral AT. Women with high visceral AT had lower glucose disposal rates compared with those with low visceral AT (P < 0.05). A similar analysis performed on two groups of women matched for visceral AT but high and low abdominal sc AT revealed no statistically different values for insulin sensitivity (P > 0.10). In conclusion, visceral AT alone is a strong correlate of insulin resistance independent of nonabdominal, abdominal sc AT, muscle composition, and cardiovascular fitness. Subdivision of abdominal sc AT did not provide additional insight into the relationship between abdominal obesity and metabolic risk.

Fixed amounts of exercise independent of exercise intensity resulted in similar reductions in abdominal obesity. Reduction in 2-hour glucose level was restricted to high-intensity exercise.

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OBJECTIVE -We investigated the effect of caffeine ingestion on insulin sensitivity in sedentary lean men (n ϭ 8) and obese men with (n ϭ 7) and without (n ϭ 8) type 2 diabetes. We also examined whether chronic exercise influences the relationship between caffeine and insulin sensitivity in these individuals.RESEARCH DESIGN AND METHODS -Subjects underwent two hyperinsulinemiceuglycemic clamp procedures, caffeine (5 mg/kg body wt) and placebo, in a double-blind, randomized manner before and after a 3-month aerobic exercise program. Body composition was measured by magnetic resonance imaging.RESULTS -At baseline, caffeine ingestion was associated with a significant reduction (P Ͻ 0.05) in insulin sensitivity by a similar magnitude in the lean (33%), obese (33%), and type 2 diabetic (37%) groups in comparison with placebo. After exercise training, caffeine ingestion was still associated with a reduction (P Ͻ 0.05) in insulin sensitivity by a similar magnitude in the lean (23%), obese (26%), and type 2 diabetic (36%) groups in comparison with placebo. Exercise was not associated with a significant increase in insulin sensitivity in either the caffeine or placebo trials, independent of group (P Ͼ 0.10).CONCLUSIONS -Caffeine consumption is associated with a substantial reduction in insulin-mediated glucose uptake independent of obesity, type 2 diabetes, and chronic exercise. Diabetes Care 28:566 -572, 2005P revious studies have shown that caffeine ingestion is associated with a marked impairment in glucose tolerance (1-4) and insulin sensitivity (5-7) in humans. Indeed, Greer et al. (6) report that moderate caffeine consumption is associated with a 24% reduction in glucose uptake in lean young men. Whether this remains true for obese individuals with or without type 2 diabetes is unknown. Conversely, it is established that both acute and chronic exercise is associated with improvements in glucose tolerance (8 -10) and insulin sensitivity (11-13) in obese and type 2 diabetic individuals. Further, Petrie et al. (2) report that caffeine ingestion is associated with an impairment in glucose tolerance, which remained after diet-and exercise-induced weight loss in a small number of obese men. Whether chronic exercise counteracts the negative effect of caffeine on insulin-mediated glucose uptake in obese individuals with and without type 2 diabetes is unknown.Given the established effects of caffeine on insulin sensitivity and that insulin resistance is an antecedent to the development of type 2 diabetes, we examined the effect of a single caffeine ingestion on insulin-mediated glucose uptake in sedentary lean men and obese men with and without type 2 diabetes. We further investigated whether 3 months of aerobic exercise without weight loss influenced caffeine-mediated insulin resistance in these individuals. RESEARCH DESIGN AND METHODS -Eight lean men (BMI Ͻ25 kg/m2 ), eight obese men with type 2 diabetes (BMI Ͼ27 kg/m 2 ), and eight obese men without type 2 diabetes (BMI Ͼ27 kg/m 2 ) were recruited from Kingston, Ontario, v...