Goals of Nutrition Therapy for Type 2 Diabetes
Nutritional management aims to help optimize metabolic control and reduce risk factors for chronic complications of diabetes.  This includes the achievement of blood glucose and glycosylated hemoglobin (HbA_1c) levels as close to normal as is safely possible, and lipid and lipoprotein profiles, as well as blood pressure values, that may be expected to reduce the risk of macrovascular disease. Individual nutritional needs and the quality of life of the person with diabetes also have to be considered when defining nutritional objectives (7 - 10,14,16,36).

The nutritional recommendation for an individual patient should include practical advice regarding appropriate food choices and quantities.  However,  it should be stressed that nutritional recommendations for people with type 2 diabetes are similar to those aimed at the population as a whole for the promotion of good health and the prevention of metabolic disorders and vascular complications. Thus, the food for persons with diabetes should not differ appreciably from that recommended for other family members (37 - 39).

Energy Restriction and Body Weight
Many individuals with type 2 diabetes are overweight.  Insulin resistance increases with increasing body weight, and obesity may also aggravate hyperlipidemia and hypertension (Fig. 1).

Many short-term studies have demonstrated that weight loss, especially of intraabdominal fat, in persons with type 2 diabetes is associated with decreased insulin resistance, improved glycemic control,  reduced blood pressure and improvement of dyslipidemia (Table 1) (35,40).

Thus, energy restriction and weight loss are important therapeutic objectives for obese individuals with type 2 diabetes (7,8,10).

However, long-term data are still scarce to assess the extent to which metabolic improvements by means of weight loss can be maintained in people with type 2 diabetes. Long-term weight loss is often difficult to achieve, and it has to be considered that genetic factors may play an important role in determining body weight.

FIGURE 1   Prevalence of hyperlipidemia and hypertension (n %)  by categories of BMI (kg m ^{- 2})  in a sample of 1988 persons with diabetes [930 male, 1058 female; mean age 57 -  13 years; mean diabetes duration 8 years].

Environmental factors also often make losing weight difficult for those genetically predisposed to obesity.

Nevertheless, the potential of structured weight loss programs should be exploited in obese persons with type 2 diabetes to achieve the possible beneficial effects.

The U.K. Prospective Diabetes Study (UKPDS) reported that the initial glucose response in persons with type 2 diabetes was particularly related to the decreased energy intake.

Once energy intake was increased, fasting glucose levels increased even when weight loss was maintained (41). Prevention of weight regain seems to be an important target in those who lose weight, but evidently a long-term restricted energy intake is necessary to sustain the metabolic improvements.

TABLE 1   Nutritional Factors and their Possible Impact on Insulin Resistance

Nevertheless, even modest weight loss of under 10% body weight improves insulin sensitivity and glucose tolerance and reduces lipid levels and blood pressure. Weight loss may lead to greater improvements in cardiac risk factors in persons with a high waist circumference (42).

Those who are overweight should be encouraged to reduce caloric intake so that their BMI moves towards the recommended range of 18.5 to 24.9 kg m ^{- 2}. Advice concerning the reduction of high fat and energy-dense foods, in particular those high in saturated fat and free sugars will usually help to achieve a weight loss. Fiber intake should be encouraged.

If such measures do not result in a desired weight reduction, it may be necessary to offer specific weight reduction programs,  which also include increased physical activity and behavior modification approaches (6,40).  The use of very low-energy diets should be restricted to persons with a BMI > 35 kg m ^{- 2}(6).

Monika Toeller
German Diabetes Research Center, Heinrich-Heine University, Düsseldorf, Germany
Jim I. Mann
Department of Human Nutrition, University of Otago, Dunedin, New Zealand

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