Control of type II diabetes. Reaping the rewards of exercise and weight loss

Dietary advice for treatment of type 2 diabetes mellitus in adults

BACKGROUND

While initial dietary management immediately after formal diagnosis is an 'accepted' cornerstone of treatment of type 2 diabetes mellitus, a formal and systematic overview of its efficacy and method of delivery is not currently available.

OBJECTIVES

To assess the effects of type and frequency of different types of dietary advice for adults with type 2 diabetes.

SEARCH STRATEGY

We carried out a comprehensive search of The Cochrane Library, MEDLINE, EMBASE, CINAHL, AMED, bibliographies and contacted relevant experts.

SELECTION CRITERIA

All randomised controlled trials, of six months or longer, in which dietary advice was the main intervention.

DATA COLLECTION AND ANALYSIS

The lead investigator performed all data extraction and quality scoring with duplication being carried out by one of the other six investigators independently with discrepancies resolved by discussion and consensus. Authors were contacted for missing data.

MAIN RESULTS

Thirty-six articles reporting a total of eighteen trials following 1467 participants were included. Dietary approaches assessed in this review were low-fat/high-carbohydrate diets, high-fat/low-carbohydrate diets, low-calorie (1000 kcal per day) and very-low-calorie (500 kcal per day) diets and modified fat diets. Two trials compared the American Diabetes Association exchange diet with a standard reduced fat diet and five studies assessed low-fat diets versus moderate fat or low-carbohydrate diets. Two studies assessed the effect of a very-low-calorie diet versus a low-calorie diet. Six studies compared dietary advice with dietary advice plus exercise and three other studies assessed dietary advice versus dietary advice plus behavioural approaches. The studies all measured weight and measures of glycaemic control although not all studies reported these in the articles published. Other outcomes which were measured in these studies included mortality, blood pressure, serum cholesterol (including LDL and HDL cholesterol), serum triglycerides, maximal exercise capacity and compliance. The results suggest that adoption of regular exercise is a good way to promote better glycaemic control in type 2 diabetic patients, however all of these studies were at high risk of bias.

AUTHORS' CONCLUSIONS

There are no high quality data on the efficacy of the dietary treatment of type 2 diabetes, however the data available indicate that the adoption of exercise appears to improve glycated haemoglobin at six and twelve months in people with type 2 diabetes. There is an urgent need for well-designed studies which examine a range of interventions, at various points during follow-up, although there is a promising study currently underway.

Focus on insulin resistance in type 2 diabetes: therapeutic implications

Type 2 diabetes is extremely common and increasing in the United States. The pathophysiology of type 2 diabetes is a combination of increased insulin resistance and inadequate secretion. The main risk factors for diabetes are family history, obesity, sedentary lifestyle, ethnic background, age, and a history of gestational diabetes. Diet and exercise, the cornerstones of diabetes management, will improve insulin sensitivity and indirectly augment insulin secretion. Until recently, the only pharmacological approaches to diabetes were sulfonylureas and insulin, which either augment insulin secretion or replace insulin, thus acting only on the insulin side of the equation. Recently, a series of new drugs have become available that are capable of decreasing hepatic glucose output (metformin), slowing postprandial glucose absorption (acarbose), and improving peripheral insulin sensitivity (troglitazone). With these drugs, either alone or in combination, and behavioral therapies, it is now feasible to achieve good to outstanding glycemic control in most individuals with type 2 diabetes.