Evidence Summary

What is an Evidence Summary?

Key messages from scientific research that's ready to be acted on

Got It, Hide this
  • Rating:

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?


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.


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. 


Clinically significant
A measurement of how effective a treatment/intervention is when applied to real-world scenarios. Assessing clinical significance takes into account factors such as the size of a treatment effect, the severity of the condition being treated, the side effects of the treatment, and the cost.
Control group
A group that receives either no treatment or a standard treatment.
Randomized controlled trials
Studies where people are assigned to one of the treatments purely by chance.
Risk factors
Aspects making a condition more likely.
Systematic review
A comprehensive evaluation of the available research evidence on a particular topic.
The body's network of blood vessels. It includes the arteries, veins, and capillaries that carry blood to and from the heart.

Related Web Resources

  • Prediabetes: Which Treatment Should I Use to Prevent Type 2 Diabetes?

    This patient decision aid helps People with prediabetes considering treatment to help prevent type 2 diabetes decide on whether to make a major lifestyle change or take the medicine metformin by comparing the benefits, risks, and side effects of both options.
  • What should I eat? Types of fat

    Harvard School of Public Health
    There are three main types of fat: unsaturated, saturated and trans fat. Unsaturated fats can help improve cholesterol levels and lower inflammation and are found in olive oil, avocados, nuts, seeds and fish. Trans fats are common in fast foods, and can increase your risk of heart disease, stroke, diabetes and other chronic conditions.
  • Medication for type 2 diabetes

    Informed Health Online
    Talk to your doctor about diabetes medications. Consider your treatment goals, age, weight, health conditions and other medications when deciding if a drug is right for you.
DISCLAIMER These summaries are provided for informational purposes only. They are not a substitute for advice from your own health care professional. The summaries may be reproduced for not-for-profit educational purposes only. Any other uses must be approved by the McMaster Optimal Aging Portal (

Register for free access to all Professional content