While the majority of studies in this review have focused on the effects of aerobic exercise, one study compared aerobic versus strength training on insulin action (48). In that study it was found that these two exercise modalities resulted in similar improvements in insulin action. This suggests that improvements in insulin action from exercise training can occur without concurrent improvements in cardiorespiratory fitness. This evidence is bolstered by results from shorter-term exercise training interventions in which no improvements in cardiorespiratory fitness were observed (4,6,29,44).
While the epidemiological data indicate that physical activity can reduce the risk of type 2 DM (19,27,33,34,41,42,49), the capacity for physical activity to improve metabolic control in the setting of established Type 2 DM is a less consistent finding. There are several recent and excellent reviews on the effect of exercise on glucose control in patients with type 2 DM (1,2,16,26,37,51), that complement earlier important studies (20,46). In general, exercise intervention results in a modest improvement of glucose control, a reduction in need for medication, or some combination of effects. In many patients improvements in glucose tolerance may not occur following exercise, and this is likely a result of a reduced capacity for insulin secretion, although other factors may also contribute. Some of the earlier studies emphasized the impact of relatively high intensity exercise to reverse or improve glucose tolerance in patients with type 2 DM and relatively mild hyperglycemia (20). More recently, several studies indicate the efficacy of milder intensity exercise to ameliorate insulin resistance in type 2 DM (5,7,12,39,52). Also, several studies indicate a favorable effect of circuit resistance training on insulin sensitivity in type 2 DM (14,25). While the insulin resistance of skeletal muscle in patients with type 2 DM is widely recognized, several recent studies find that during exercise rates of glucose utilization are moderately increased compared with nondiabetic subjects exercising at the same intensity (8,17,28,35).
This review has outlined recent research on the effects of physical activity upon glucose tolerance and insulin sensitivity in obesity. The evidence suggests that exercise training does have a beneficial effect on glucose and insulin homeostasis and, most particularly, on insulin resistance. However, several important questions remain. There are not enough data concerning exercise and glucose homeostasis in women and minorities. More information would be useful to examine the interaction of body composition changes and improvements in insulin action as a result of exercise training. Given the strong association between regional adipose tissue depots, fatty acids, and insulin resistance of obesity, this area deserves further investigation with respect to exercise. For example, King et al. (32) showed that insulin action immediately following exercise was impaired because of elevated levels of circulating fatty acids, which have been shown to induce insulin resistance (31). It has also been recently demonstrated that an accumulation of intramuscular triglyceride is associated with insulin resistance in obesity (40). In young lean individuals, exercise training improves the ability to oxidize intramuscular fatty acids (24); however, data regarding the effects of exercise training on substrate selection in obesity and how this may influence insulin action are scarce. Finally, and of greatest importance is how much, at what intensity, and how often should exercise be done to obtain favorable effects on health (3,13).
1. American College of Sports Medicine and American Diabetes Association. Joint Position Statement: Diabetes Mellitus
. Med. Sci. Sports Exerc. 29: i–iv, 1997.
2. American Diabetes Association. Clinical Practice Recommendations: Diabetes Mellitus
. Diabetes Care 22: S49–S53, 1999.
3. Anderson, R. E., T. A. Wadden, S. J. Barlett, B. Zemel, T. Verde, and S. Frackowiak. Effects of lifestyle activity vs structured aerobic exercise
in obese women: a randomized trial. JAMA 281: 335–340, 1999.
4. Angelopoulos, T. J., R. Lewis, T. Jamurtas, and C. Schumann. Significant changes in VLDL-triacylglycerol and glucose tolerance
in obese subjects following ten days of training. Eur. J. Appl. Physiol. Occup. Physiol. 77: 556–9, 1998.
5. Braun, B., M. B. Zimmerman, and N. Kretchmer. Effects of exercise
intensity on insulin sensitivity in women with non-insulin-dependent diabetes mellitus
. J. Appl. Physiol. 78: 300–306, 1995.
6. Brown, M. D., G. E. Moore, M. T. Korytkowski, S. D. McCole, and J. M. Hagberg. Improvement of insulin sensitivity by short-term exercise
training in hypertensive African-American women. Hypertension 30: 1549–53, 1997.
7. Clark, D. O. Physical activity efficacy and effectiveness among older adults and minorities. Diabetes Care 20: 1176–1182, 1997.
8. Colberg, S., J. Hagberg, S. M. McCole, J. Zmuda, P. Thompson, and D. E. Kelley. Utilization of glycogen but not plasma glucose is reduced in individuals with NIDDM during mild-intensity exercise
. J. Appl. Physiol. 84: 2027–2033, 1996.
9. Dengel, D. R., J. M. Hagberg, R. E. Pratley, E. M. Rogus, and A. P. Goldberg. Improvements in blood pressure, glucose metabolism, and lipoprotein lipids after aerobic exercise
plus weight loss in obese, hypertensive middle-aged men. Metabolism 47: 1075–1082, 1998.
10. Dengel, D. R., R. E. Pratley, J. M. Hagberg, E. M. Rogus, and A. P. Goldberg. Distinct effects of aerobic exercise
training and weight loss on glucose homeostasis in obese sedentary men. J. Appl. Physiol. 81: 318–25, 1996.
11. Després, J.-P. Abdominal obesity
as important component of insulin resistance syndrome. Nutrition 9: 452–459, 1993.
12. 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. Ger. Soc. 46: 875–879, 1998.
13. Dunn, A., B. Marcus, J. Kampert, M. Garcia, H. Kohl, and S. Blair. Comparison of lifestyle and structured interventions to increase physical activity and cardiorespiratory fitness: a randomized trial. JAMA 281: 337–334, 1999.
14. Eriksson, J., J. Tuominen, T. Valle, et al. Aerobic endurance exercise
or circuit-type resistance training for individuals with impaired glucose tolerance
? Hormone Metab. Res. 30: 37–41, 1998.
15. Eriksson, K. F. and F. Lindgarde. No excess 12-year mortality in men with impaired glucose tolerance
who participated in the Malmo preventive trial with diet and exercise
. Diabetologia 41: 1010–1016, 1998.
16. Gautier, J. F., A. Scheen, and P. J. Lefebvre. Exercise
in the management of non-insulin-dependent (type 2) diabetes mellitus
. Int. J. Obes. 19(Suppl. 4): S58-S61, 1995.
17. Giacca, A., Y. Groenewoud, E. Tsue, P. McClean, and B. Zinman. Glucose production, utilization and cycling in response to moderate exercise
in obese subjects with type 2 diabetes and mild hyperglycemia. Diabetes 47: 1763–1770, 1998.
18. Hellenius, M. L., K. E. Brismar, B. H. Berglund, and U. H. de Faire. Effects on glucose tolerance
, insulin secretion, insulin-like growth factor 1 and its binding protein, IGFBP-1, in a randomized controlled diet and exercise
study in healthy, middle-aged men. J. Intern. Med. 238: 121–30, 1995.
19. Helmrich, S. P., D. R. Ragland, R. W. Leung, and R. S. Paffenbarger. Physical activity and reduced occurrence of non-insulin-dependent diabetes mellitus
. N. Engl. J. Med. 325: 147–152, 1991.
20. Holloszy, J. O., J. Schultz, J. Kusnierkiewicz, J. M. Hagberg, and A. A. Ehsani. Effects of exercise
on glucose tolerance
and insulin resistance: brief review and some preliminary results. Acta Med. Scand.-Suppl. 711: 55–65, 1986.
21. Houmard, J. A., M. H. Shinebarger, P. L. Dolan, et al. Exercise
training increases GLUT-4 protein concentration in previously sedentary middle-aged men. Am. J. Physiol. 264: E896-E901, 1993.
22. Hughes, V. A., M. A. Fiatarone, R. A. Fielding, C. M. Ferrara, D. Elahi, and W. J. Evans. Long-term effects of a high-carbohydrate diet and exercise
on insulin action in older subjects with impaired glucose tolerance
. Am. J. Clin. Nutr. 62: 426–33, 1995.
23. Hughes, V. A., M. A. Fiatarone, R. A. Fielding, et al. Exercise
increases muscle GLUT-4 levels and insulin action in subjects with impaired glucose tolerance
. Am. J. Physiol. 264: E855-E62, 1993.
24. Hurley, B. F., P. M. Nemeth, W. H. D. Martin, J. M. Hagberg, G. P. Dalsky, and J. O. Holloszy. Muscle triglyceride utilization during exercise
: effect of training. J. Appl. Physiol. 60: 562–7, 1986.
25. Ishii, T., T. Yamakita, T. Sato, S. Tanaka, and S. Fujii. Resistance training improves insulin sensitivity in NIDDM subjects without altering maximal oxygen uptake. Diabetes Care 21: 1353–1355, 1998.
26. Ivy, J. Role of exercise
training in the prevention and treatment of insulin resistance and non-insulin-dependent diabetes mellitus
. Sports Med. 24: 321–336, 1997.
27. James, S. A., L. Jamjoum, T. E. Raghunathan, D. S. Strogatz, E. D. Furth, and P. G. Khazanie. Physical activity and NIDDM in African-Americans. The Pitt County Study. Diabetes Care 21: 555–562, 1998.
28. Kang, J., D. E. Kelley, R. J. Robertson, et al. Substrate utilization and glucose turnover during exercise
of varying intensities in individuals with NIDDM. Med. Sci. Sports Exerc. 31: 82–89, 1999.
29. Kang, J., R. J. Robertson, J. M. Hagberg, et al. Effect of exercise
intensity on glucose and insulin metabolism in obese individuals and obese NIDDM patients. Diabetes Care 19: 341–9, 1996.
30. Katzel, L. I., E. R. Bleecker, E. G. Colman, E. M. Rogus, J. D. Sorkin, and A. P. Goldberg. Effects of weight loss vs aerobic exercise
training on risk factors for coronary disease in healthy, obese, middle-aged and older men: a randomized controlled trial. JAMA 274: 1915–21, 1995.
31. Kelley, D. E. and J.-A. Simoneau. Impaired free fatty acid utilization by skeletal muscle in non-insulin-dependent diabetes mellitus
. J. Clin. Invest. 94: 2349–2356, 1994.
32. King, D. S., P. J. Baldus, R. L. Sharp, L. D. Kesl, T. L. Feltmeyer, and M. S. Riddle. Time course for exercise
-induced alterations in insulin action and glucose tolerance
in middle-aged people. J. Appl. Physiol. 78: 17–22, 1995.
33. Manson, J. E., D. M. Nathan, A. S. Krolewski, M. J. Stampfer, W. C. Willett, and C. H. Hennekens. A prospective study of exercise
and incidence of diabetes among U.S. male physicians. JAMA 268: 63–7, 1992.
34. Manson, J. E., E. B. Rimm, M. J. Stampfer, et al. Physical activity and incidence of non-insulin-dependent diabetes mellitus
in women. Lancet 338: 774–8, 1991.
35. Martin, I. K., A. Katz, and J. Wahren. Splanchnic and muscle metabolism during exercise
in NIDDM patients. Am. J. Physiol. 269 (Endocrinol. Metab. 32): E583-E590, 1995.
36. Mayer-Davis, E. J., R. D’Agostino, Jr., A. Karter, et al. Intensity and amount of physical activity in relation to insulin sensitivity: the Insulin Resistance Atherosclerosis Study. JAMA 279: 669–674, 1998.
37. National Institutes of Health Consensus Development Conference Statement. Diet and exercise
in non-insulin-dependent diabetes mellitus
. Nutrition 13: 89–94, 1997.
38. 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): S51–S209, 1998.
39. Ohtsuka, Y., N. Yabunaka, and S. Takayama. Shinrin-yoku effectively decreases blood glucose levels in diabetic patients. Int. J. Biometerol. 41: 125–127, 1998.
40. Pan, D. A., S. Lillioja, A. D. Kriketos, et al. Skeletal muscle triglyceride levels are inversely related to insulin action. Diabetes 46: 983–988, 1997.
41. Pan, X. R., G. W. Li, Y. H. Hu, et al. Effects of diet and exercise
in preventing NIDDM in people with impaired glucose tolerance
: The Da Qing IGT and diabetes study. Diabetes Care 20: 537–544, 1997.
42. Perry, I. J., S. G. Wannamethee, M. K. Walker, et al. Prospective study of risk factors for development of non-insulin dependent diabetes in middle aged British men. Br. Med. J. 310: 560–564, 1995.
43. Perseghin, G., T. B. Price, K. F. Petersen, et al. Increased glucose transport-phosphorylation and muscle glycogen synthesis after exercise
training in insulin-resistant subjects. N. Engl. J. Med. 335: 1357–1362, 1996.
44. Rogers, M. A., C. Yamamoto, D. S. King, J. M. Hagberg, A. A. Ehsani, and J. O. Holloszy. Improvement in glucose tolerance
after 1 week of exercise
in patients with mild NIDDM. Diabetes Care 11: 613–618, 1988.
45. Saltin, B. and P. D. Gollnick. Skeletal muscle adaptability: significance for metabolism and performance. In:Handbook of Physiology, Sect. 10: Skeletal Muscle
. Chap. 19, L. D. Peachy (Ed.). Baltimore: Williams & Wilkins, 1983 pp. 555–631.
46. Schneider, S. H., L. F. Amorosa, A. K. Khachadurian, and N. B. Ruderman. Studies on the mechanism of improved glucose control during regular exercise
in Type 2 (non-insulin-dependent) diabetes. Diabetologica 26: 355–360, 1984.
47. Segal, K. R., A. Edano, A. Abalos, et al. Effect of exercise
training on insulin sensitivity and glucose metabolism in lean, obese, and diabetic men. J. Appl. Physiol. 71: 2402–11, 1991.
48. Smutok, M. A., C. Reece, P. F. Kokkinos, et al. Effects of exercise
training modality on glucose tolerance
in men with abnormal glucose regulation. Int. J. Sports Med. 15: 283–289, 1994.
49. Takemura, Y., S. Kikuchi, Y. Inaba, H. Yasuda, and K. Nakagawa. The protective effect of good physical fitness when young on the risk of impaired glucose tolerance
when old. Prev. Med. 28: 14–19, 1999.
50. Uusitupa, M. I. Early lifestyle intervention in patients with non-insulin-dependent diabetes mellitus
and impaired glucose tolerance
. Ann. Med. 28: 445–9, 1996.
51. Wallberg-Henriksson, H., J. Rincon, and J. R. Zierath. Exercise
in the management of non-insulin-dependent diabetes mellitus
. Sports Med. 25: 25–35, 1998.
52. Yamanouchi, K., T. Shinozaki, K. Chikada, et al. Daily walking combined with diet therapy is a useful means for obese NIDDM patients not only to reduce body weight but also to improve insulin sensitivity. Diabetes Care 18: 775–778, 1995.