Only three RCT and three nonrandomized studies meeting the inclusion criteria report whether physical activity is associated with reductions in visceral fat (Table 3). From these studies, although it is generally reported that physical activity is associated with reductions in visceral fat, it is not possible to establish a dose-response relationship. The latter observation may be explained in part by the relatively low levels of visceral fat before treatment for several of the studies reviewed. For example, in three of the four studies that report only minor reduction in visceral fat in response to exercise (8,11,42; young men), initial visceral fat values were, in general, low by comparison with those studies that observed substantial reductions in visceral fat. Whether a threshold exists below which the mobilization of visceral fat in response is markedly reduced, is unknown.
Absent from the literature are studies that systematically consider the influence of various levels of physical activity on the reduction of total or abdominal obesity. As a consequence, our consideration of whether a dose-response relationship existed between physical activity and obesity reduction required that we perform a regression analysis inherent to which were several assumptions. First, because the majority of studies reviewed required that we estimate energy expenditure on the basis of mean values for O2max, exercise intensity, duration, and frequency (Tables 1 and 2), our regression analysis was dependent on estimates of exercise-induced energy expenditure. Second, although the average exercise-induced energy expenditure values in the studies examined ranged from 500 to 5500 kcal·wk-1, in 75% of the studies energy expended by exercise fell below 1800 kcal·wk-1 (Fig. 1 and Tables 1 to 3). Finally, unlike a meta-analysis, we made no attempt to weigh the studies on the basis of, for example, the number of participants in each study. Together, these limitations suggest that the dose-response relationship observed between exercise and obesity reduction be interpreted with caution.
The conclusions of this review are derived in large measure from studies that use middle-aged male, Caucasian subjects; as such, the influence of age and race is unknown. With respect to gender, although 19 of the 31 studies incorporated female subjects, inspection of Tables 1 and 2 reveals that only three nonrandomized trials prescribed exercise for women of a magnitude greater than ∼1500 kcal·wk-1. A rationale that would support the exclusion of women in studies wherein exercise is performed for longer durations is unknown. To the contrary, there is evidence to support the notion that women may be at an advantage when it comes to performing submaximal exercise. Indeed, during moderate-intensity long-duration exercise, females demonstrate a greater lipid and lower carbohydrate oxidation compared with men (7,45). A greater reliance on lipid as a fuel during submaximal exercise would spare muscle glycogen and thus, in theory, delay time to fatigue. Theses observations support the view that women are capable of performing moderate-intensity exercise of a sufficient duration and frequency to induce substantial weight loss.
Address for correspondence: Robert Ross, Ph.D., School of Physical and Health Education, Queen’s University, Kingston, Ontario, Canada K7L 3N6; E-mail: firstname.lastname@example.org.
1. American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription
, 5th Ed. Baltimore, MD: Williams & Wilkins, 1995, pp. 275–283.
2. Binder, E. F., S. J. Birge, and W. M. Kohrt. Effects of endurance exercise and hormone replacement therapy on serum lipids in older women. J. Am. Geriatr. Soc. 44: 231–236, 1996.
3. Boileau, R. A., E. R. Buskirk, D. H. Horstman, J. Mendez, and W. C. Nicholas. Body composition changes in obese and lean men during physical conditioning. Med. Sci. Sports Exerc. 3: 183–189, 1971.
4. Bouchard, C., F. T. Dionne, J.-A. Simoneau, and M. R. Boulay. Genetics of aerobic and anaerobic performance. Exerc. Sport Sci. Rev. 20: 27–58, 1992.
5. Bouchard, C., A. Tremblay, J.-P. Després, et al. The response to exercise with constant energy intake in identical twins. Obes. Res. 2: 400–410, 1994.
6. Coggan, A. R., R. J. Spina, D. S. King, et al. Skeletal muscle adaptations to endurance training in 60- to 70-yr-old men and women. J. Appl. Physiol. 72: 1780–1786, 1992.
7. Davis, S. N., P. Galassetti, D. H. Wasserman, and D. Tate. Effects of gender on neuroendocrine and metabolic counterregulatory responses to exercise in normal man. J. Clin. Endocrinol. Metab. 85: 224–230, 2000.
8. Després, J.-P., M.-C. Pouliot, S. Moorjani, et al. Loss of abdominal fat
and metabolic response to exercise training in obese women. Am. J. Physiol. 261: E159–E167, 1991.
9. Dipietro, L. Physical activity
in the prevention of obesity
: current evidence and research issues. Med. Sci. Sports Exerc. 31: S542–S546, 1999.
10. Dipietro, L., H. W. Kohl III, C. E. Barlow, and S. N. Blair. Improvements in cardiorespiratory fitness attenuate age-related weight gain in healthy men and women: the aerobics center longitudinal study. Int. J. Obes. 22: 55–62, 1998.
11. Dipietro, L., T. E. Seeman, N. S. Stachenfeld, L. D. Katz, and E. R. Nadel. Moderate-intensity aerobic training improves glucose tolerance in aging independent of abdominal adiposity. J. Am. Geriatr. Soc. 46: 875–879, 1998.
12. Farrell, P. A., and J. Barboriak. The time course of alterations in plasma lipid and lipoprotein concentrations during eight weeks of endurance training. Atherosclerosis 37: 231–238, 1980.
13. French, S. A., R. W. Jeffrey, J. L. Foster, P. G. Mcgovern, S. H. Kelder, and J. E. Baxter. Predictors of weight change over two years among a population of working adults: the Healthy Work Project. Int. J. Obes. 18: 145–154, 1994.
14. Frey-Hewitt, B., K. M. Vranizan, D. M. Dreon, and P. D. Wood. The effect of weight loss
by dieting or exercise on resting metabolic rate (RMR) in overweight men. Int. J. Obes. 14: 327–334, 1990.
15. Gallagher, D., S. B. Heymsfield, M. Heo, S. A. Jebb, P. R. Murgatroyd, and Y. Sakamoto. Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. Am. J. Clin. Nutr. 72: 694–701, 2000.
16. Gordon, N. F., C. B. Scott, and B. D. Levine. Comparison of single versus multiple lifestyle interventions: are antihypertensive effects of exercise training and diet-induced weight loss
additive? Am. J. Cardiol. 79: 763–767, 1997.
17. Gredigan, M. A., M. Cody, J. Rupp, D. Denardot, and R. Shern. Exercise intensity does not effect body composition change in untrained, moderately overfat women. J. Am. Diet. Assoc. 95: 661–665, 1995.
18. Grundy, S. M., G. Blackburn, M. Higgins, R. Lauer, M. G. Perri, and D. Ryan. Roundtable consensus statement: physical activity
in the prevention and treatment of obesity
and its comorbidities. Med. Sci. Sports Exerc. 31: S502–S508, 1999.
19. Goran, M. I., and E. T. Poehlman. Endurance training does not enhance total energy expenditure in healthy elderly persons. Am. J. Physiol. 263: E950–E957, 1992.
20. Gordon, N. F., C. B. Scott, and B. D. Levine. Comparison of single versus multiple lifestyle interventions: are the antihypertensive effects of exercise training and diet-induced weight loss
additive? Am. J. Cardiol. 79: 763–767, 1997.
21. Hagan, R. D., S. J. Upton, L. Wong, and J. Whittam. The effects of aerobic conditioning and/or caloric restriction in overweight men and women. Med. Sci. Sports Exerc. 18: 87–94, 1986.
22. Hinkleman, L., and D. C. Nieman. The effects of a walking program on body composition and serum lipids and lipoproteins in overweight women. J. Sports Med. Phys. Fitness 33: 49–58, 1993.
23. Houmard, J. A., C. McCulley, L. K. Roy, R. K. Bruner, M. R. McCammon, and R. G. Israel. Effects of exercise training on absolute and relative measurements of regional adiposity. Int. J. Obes. 18: 243–248, 1994.
24. Keim, N. L., T. F. Barbieri, M. D. Vanloan, and B. L. Anderson. Energy expenditure and physical performance in overweight women: response to training with and without caloric restriction. Metabolism 39: 651–658, 1990.
25. Kohrt, W. M., A. A. Ehsani, and S. J. Birge Jr. Effects of exercise involving predominantly either joint-reaction or ground-reaction forces on bone mineral density (BMD) in women. J. Bone Miner. Res. 12: 1253–1261, 1997.
26. Kohrt, W. M., K. A. Obert, and J. O. Holloszy. Exercise training improves fat distribution patterns in 60- to 70-year-old men and women. J. Gerontol. Med. Sci. 47: M99–M105, 1992.
27. Kollias, J., J. S. Skinner, H. L. Barlett, B. S. Bergstiinova,and E. R. Buskirk. Cardiorespiratory responses to young and overweight women to ergometry following modest weight reduction. Arch. Environ. Health 27: 61–64, 1973.
28. Lamarche, B., J.-P. Després, M.-C. Pouliot, et al. Is body fat loss a determinant factor in the improvement in carbohydrate and lipid metabolism following aerobic exercise training in obese women? Metabolism 41: 1249–1256, 1992.
29. Leon, A. S., J. Conrad, D. B. Hunninghake, and R. Serfass. Effects of a vigorous walking program on body composition, and carbohydrate and lipid metabolism of obese young men. Am. J. Clin. Nutr. 33: 1776–1787, 1979.
30. Mourier, A., J. F. Gautier, E. De Kerviler, et al. Mobilization of visceral adipose tissue related to the improvement in insulin sensitivity in response to physical training in NIDDM. Diabetes Care 20: 385–391, 1997.
31. National Institutes of Health; National Heart, Lung, and Blood Institute. Clinical guidelines on the identification, evaluation, and treatment of overweight and obesity
in adults: the evidence report. Obes. Res.
6(Suppl. 2):51S–210S, 1998.
32. Pate, R. R., M. Pratt, S. N. Blair, et al. Physical activity
and public health: a recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA 273: 402–407, 1995.
33. Poehlman, E. T., A. W. Gardner, P. J. Archiero, M. I. Goran, and J. Calles-Escandon. Effects of endurance training on total fat oxidation in elderly persons. J. Appl. Physiol. 76: 2281–2287, 1994.
34. Poirier, P., C. Catillier, A. Tremblay, and A. Nadeau. Role of body fat loss in the exercise-induced improvement of the plasma lipid profile in non-insulin-dependent diabetes mellitus. Metabolism 45: 1383–1387, 1996.
35. Posner, J. D., K. M. Gorman, L. W. Windsor-Landsberg, et al. Low to moderate intensity endurance training in healthy older adults: physiological responses after four months. J. Am. Geriatr. Soc. 40: 1–7, 1992.
36. Ready, A. E., D. T. Drinkwater, J. Ducas, D. W. Fitzpatrick, D. G. Brereton, and S. C. Oades. Walking program reduces elevated cholesterol in women postmenopause. Can. J. Cardiol. 11: 905–912, 1995.
37. Reid, C. M., A. M. Dart, E. M. Dewar, and G. L. Jennings. Interactions between the effects of exercise and weight loss
on risk factors, cardiovascular haemodynamics and left ventricular structure in overweight subjects. J. Hypertens. 12: 291–301, 1994.
38. Ross, R., D. Dagnone, P. H. J. Jones, et al. Reduction in obesity
and related comorbid conditions after diet-induced weight loss
or exercise-induced weight loss
in men: a randomized controlled trail. Ann. Intern. Med. 133: 92–103, 2000.
39. Ross R., J. A. Freeman, and I. Janssen. Exercise alone is an effective strategy for reducing obesity
and related comorbidities. Exerc. Sport Sci. Rev. 28: 65–70, 2000.
40. Ross, R., and I. Janssen. Is abdominal fat
preferentially reduced in response to exercise-induced weight loss
? Med. Sci. Sports Exerc. 31: S568–S572, 1999.
41. Schwartz, R. S. The independent effects of dietary weight loss
and aerobic training on high density lipoprotein (HDL) and apolipoprotein A-I concentrations in obese men. Metabolism 36: 165–171, 1987.
42. Schwartz, R. S., W. P. Shuman, V. Larson, et al. The effect of intensive endurance exercise training on body fat distribution in young and older men. Metabolism 40: 545–551, 1991.
43. Smutok, M. A., C. Reece, P. F. Kokkinos, et al. Aerobic versus strength training for risk factor intervention in middle-aged men at risk for coronary heart disease (CHD). Metabolism 42: 177–184, 1993.
44. Sopko, G., A. S. Leon, D. R. Jacobs, et al. The effects of exercise and weight loss
on plasma lipids in young obese men. Metabolism 34: 227–236, 1985.
45. Tarnopolsky, L. J., J. D. MacDougall, S. A. Atkinson, M. A. Tarnopolsky, and J. R. Sutton. Gender differences in substrate for endurance exercise. J. Appl. Physiol. 68: 302–308, 1990.
46. Weltman, A., S. Matter, and B. A. Stamford. Caloric restriction and/or mild exercise: effects on serum lipids and body composition. Am. J. Clin. Nutr. 33: 1002–1009, 1980.
47. Williamson, D. F., J. Madans, R. F. Anda, J. C. Kleinman, H. Kahn, and T. Byers. Recreational physical activity
and ten-year weight change in a US national cohort. Int. J. Obes. 17: 279–286, 1993.
48. Wood, P. D., M. L. Stefanick, D. M. Dreon, et al. Changes in plasma lipids and lipoproteins in overweight men during weight loss
through dieting as compared with exercise. N. Engl. J. Med. 319: 1173–1179, 1988.