Last updated: June 25, 2014
Project Number: RC0564-001
Research Type: Devices and Systems
Report Type: Summary with Critical Appraisal
Result type: Report
Report in Brief
Type 2 diabetes is a chronic disease characterized by high blood glucose that occurs when the pancreas does not produce enough insulin, or the body does not properly use the insulin that it makes. Excess body weight can contribute to the development of diabetes, and some antidiabetic medications can further increase body weight. In 2012, 14.7% of obese Canadians 18 years or older had diabetes compared with 5.1% of those who were not obese. The benefits of weight loss in overweight or obese patients with type 2 diabetes include enhanced glycemic control, improved mobility, and a decreased need for some medications.
Treatments for obesity decrease caloric intake or increase energy expenditure. Strategies for weight loss in obese patients with type 2 diabetes include lifestyle interventions such as dietary adjustment and increased physical activity, as well as pharmacological interventions. An initial weight loss goal of 5% to 7% of body weight is realistic for many patients with diabetes.
Given the importance of weight loss in potentially halting or slowing the progression of type 2 diabetes, a review of the clinical effectiveness of long-term obesity management interventions in primary care will help to guide decisions about how best to approach weight loss in patients with type 2 diabetes.
A limited literature search was conducted of key resources, and titles and abstracts of the retrieved publications were reviewed. Full-text publications were evaluated for final article selection according to predetermined selection criteria.
The literature search identified 461 citations, 25 of which were deemed potentially relevant. An additional 10 reports were identified from other sources. Of these 35 reports, 10 met the criteria for inclusion in this review: 5 unique randomized controlled trials (RCTs), and 5 additional articles conducting secondary analysis of the unique RCTs.
For weight loss in obese and overweight patients with type 2 diabetes:
- Decreasing caloric intake results in greater short-term (six months) weight loss than increasing physical activity.
- A combination of diet and exercise are necessary to achieve and maintain weight loss in the long term (12 months or more).
- More patients using drug interventions achieve weight reductions of 5% or more than patients following lifestyle interventions.
- Weight loss is linked to better glycemic control, improved quality of life, reduced mobility loss, reduced or discontinued antidiabetes medications, and decreased mortality.
- What is the clinical effectiveness of long-term primary care obesity management interventions in halting or slowing the progression of type 2 diabetes?
In using a lifestyle approach to achieve weight loss in overweight or obese patients with type 2 diabetes, it has been shown that decreasing caloric intake produced greater weight loss than physical activity in the short-term (6 months); however, a combination of diet and exercise were needed to achieve and maintain weight loss in the long-term (12 months). Significantly greater proportions of patients using pharmacological interventions achieved reductions of 5% or more of their initial weight compared to those receiving a standardized lifestyle intervention. Weight loss in overweight/obese type 2 diabetes patients was associated with better glycemic control (as demonstrated by improved insulin sensitivity, fasting blood glucose, and HbA1c), improved quality of life, and reduced risk of loss of mobility. Satisfactory weight reductions were achieved when energy expenditure was increased to 1000 kcal/day and beyond, and improvements in glucose control appeared to be associated with weight loss of 5% or more. Improvements in blood glucose control resulted in reduction (in some cases discontinuation) of antidiabetic medication usage for some patients. Despite challenges faced by some obese patients with type 2 diabetes to reach the threshold weight loss ( 5% initial body weight) required to realize clinically meaningful glycemic control, continued efforts have been encouraged given that modest intentional weight loss can improve cardiovascular risk factors and decrease mortality.