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Lifestyle changes lower rates of type 2 diabetes among adults at increased risk, but may not prevent complications in those already diagnosed

Schellenberg ES, Dryden DM, Vandermeer B et al. [TITLE]. Ann Intern Med. 2013; 159(8): 543-551.

Review questions

Do lifestyle interventions help prevent adults at risk of type 2 diabetes from getting the disease? Do they help prevent complications (such as cardiovascular disease and death) in adults already diagnosed with type 2 diabetes?

Background

Obesity and physical inactivity are known risk factors for type 2 diabetes.  Programs that promote lifestyle changes to address these risk factors can help prevent and manage type 2 diabetes.

How the review was done

This is a systematic review of 20 randomized controlled trials, 9 involving adults at high risk for type 2 diabetes and 11 involving adults who already have the disease.  

Lifestyle interventions lasted at least six months and included an exercise program, dietary changes and at least one other component such as counseling, smoking cessation or behavior modification.  Participants ranged in age from 44 to 85 years. The smallest study had 39 participants; the largest had 3,234 participants.

The studies measured how many people developed type 2 diabetes (from the high risk groups) and/or how many developed health complications.  The studies also measured ‘warning signs’ for health complications, such as high blood pressure, physical inactivity, diet, blood sugar and body composition. Comparison or control groups were people receiving the usual care from their physicians, people participating in just diet or exercise programs (not both at the same time), or people on a waiting list to join the programs.

What the researchers found

Seven studies found that lifestyle interventions helped prevent type 2 diabetes in adults at risk. Two studies found that lifestyle interventions did not reduce the risk of death for adults already diagnosed with type 2 diabetes. Many of the studies reported positive health effects (i.e. change in diet, physical activity, body composition and metabolic measures) for both adults at risk and adults with type 2 diabetes but the improvements were not always statistically or clinically significant, or continued after the programs ended.

Conclusion

Lifestyle interventions that focus on exercise, diet and other positive changes can help prevent type 2 diabetes among those at risk of developing the disease. However there was not enough evidence to suggest that this approach helps prevent health complications in people who already have type 2 diabetes.