Exercise, dietary changes and medications are frequently used in the management of type 2 diabetes. However, it is difficult to determine the independent effect of exercise from some trials because exercise has been combined with dietary modifications or medications, or compared with a control which includes another form of intervention. The review authors aimed to determine the effect of exercise on blood sugar control in type 2 diabetes.
This review found that exercise improves blood sugar control and that this effect is evident even without weight loss. Furthermore, exercise decreases body fat content, thus the failure to lose weight with exercise programmes is probably explained by the conversion of fat to muscle. Exercise improved the body's reaction to insulin and decreased blood lipids. Quality of life was only assessed in one study, which found no difference between the two groups. No significant difference was found between groups in blood levels of cholesterol or blood pressure. A total of 14 randomised controlled trials were assessed. These included 377 participants and compared groups that differed only with respect to an exercise programme intervention. The duration of the interventions in the studies ranged from eight weeks to one year. Two studies reported follow-up information, one at six months after the end of the six month exercise intervention and one at twelve months post-intervention. Generally, the studies were well-conducted, but blinding of outcome assessors was not reported and although all studies reported that randomisation was performed, few gave details of the method.
No adverse effects with exercise were reported. The effect of exercise on diabetic complications was not assessed in any of the studies.
The relatively short duration of trials prevented the reporting of any significant long term complications or mortality. Another limitation was the small number of participants included in the analyses for adiposity, blood pressure, cholesterol, body's muscle and quality of life.