Weight loss is the best documented intervention for controlling blood glucose levels in patients who have type 2 diabetes. Several trials have demonstrated that hypocaloric diets substantially reduce blood glucose levels; however, it is less clear whether glucose improvement is related to actual weight loss or simply to the temporarily decreased caloric intake that takes place during the weight reduction period. Moreover, weight loss as a tool for glycemic control is often unsatisfactory because of the patient's inability to lose weight or to sustain a successful weight reduction.

Link discusses the value of having diabetic patients eat small frequent meals rather than several large meals, based on the patient's ability to retain an adequate insulin response to modest carbohydrate load but inability to cope with larger carbohydrate intakes. Patients with type 2 diabetes (formerly called non–insulin-dependent diabetes) with multiple daily-meal regimens have shown a reduction in the daily amplitude of glucose swings (between highest and lowest levels) and a decrease in peak glucose levels, but the average glucose levels remained unaffected because glucose lows were attenuated. Other studies have demonstrated that eating frequent meals throughout the day reduces mean insulin levels. The problems with frequent meals, however, include the potential of weight gain and the difficulty with compliance. Long-term studies on the effectiveness of frequent meals in reducing diabetes morbidity are necessary.

The appropriate composition of carbohydrates in the diet for type 2 diabetes is uncertain. The effects of fat and fiber on gastric emptying and intestinal absorption make the results of carbohydrate studies unpredictable. The glycemic index is a standardized measure of blood glucose response to the ingestion of given substances that provides the equivalent carbohydrate content of different foods. Using white bread as a standard glycemic index of 100, the equivalent for honey is 126, sucrose 86, bananas 79 and ice cream 52. However, even these relatively standardized figures vary in response to mixed meals. Because carbohydrates of all types are chief contributors to hyperglycemia, sweets may occasionally be substituted for complex carbohydrates without harming glucose control in patients who have cravings.

Fat intake has traditionally been strictly controlled in the dietary recommendations of the American Diabetes Association, with carbohydrates being the preferred energy source. Recent data support the use of a diet high in monounsaturated fats over a diet high in carbohydrates because monounsaturated fats have been shown to decrease glucose, triglyceride and insulin levels. The long-term effect of a diet high in monounsaturated fats has not been fully assessed, but type 2 diabetic patients should emphasize a diet high in monounsaturated fats over other dietary fats. In refractory cases, monounsaturated fats may replace carbohydrates, but weight and lipid profile should be closely monitored.

The author concludes that optimal diet control in type 2 diabetic patients who have fluctuating glucose levels during the day can be achieved by reducing the size of meals, eating small snacks and adding sweets to the daily carbohydrate quota to prevent cravings. Monounsaturated fats should be emphasized; inadequate data do not support an increase in daily total fat intake. All of these parameters should be integrated into a mildly hypocaloric diet.

editor's note: The American Diabetes Association's dietary guidelines for diabetic patients include lowering the total fat intake, especially saturated and polyunsaturated fats. The bulk intake of calories should come from monounsaturated fats and carbohydrates, depending on individual desire and other clinical information. Carbohydrate intake should be spread throughout the day to prevent peaks and valleys in the serum glucose concentration. High-fiber foods are always encouraged. Several nutrition experts are now promoting diets high in monounsaturated fats at the expense of carbohydrates. Recent research is demonstrating that high-density lipoprotein (HDL) cholesterol levels are actually higher in patients who ingest a lowglycemic index and high-monounsaturated diet, compared with a high-glycemic diet. A beneficial effect on glucose metabolism in patients who have controlled type 2 diabetes has not been demonstrated.—r.s.