The majority of patients with diabetes mellitus (DM) are classified as non-insulin dependent diabetes mellitus (NIDDM). This group retains significant endogenous insulin secretory capacity. Although oral hypoglycemic agents or insulin may be necessary for the glycemic control of NIDDM in some patients, diet and exercise could be an essential part of treatment.^1–5) However, there have been few reports from Korea on the effects of diet and exercise as therapy for the control of DM.

In this paper, the effect of strict diet and exercise therapy on glycemic control studied in 147 NIDDM patients is reported. An effort was made to find other possible factors related to glycemic control.

The short-term success group totaled 112 cases (76%). This included 78 cases (53%) who belonged to the success group and 34 cases (23%) who belonged to the induction group (Table 2). The long-term success rate in obese NIDDM patients was slightly greater than that of non-obese NIDDM patients, but not significantly so (Table 2, 3). Our program did not result in significant weight reduction in any groups (Table 4).

In both types of NIDDM, the duration of DM in the short-term and long-term success groups was significantly shorter than that in the short-term and long-term failure groups (Table 5). Previous history of having taken oral hypoglycemic agents and complications in the short-term and the long-term success groups was significantly more numerous than those in the short-term and the long-term failure groups (Table 6, 7).

There were no significant differences in initial FBS and HbA_1c levels among the different groups (Table 8, 9). There was no significant difference between the basal or the peak C-peptide levels of the short-term success and those of the short-term failure groups of both types of NIDDM (Table 10). However, the peak C-peptide levels of the long-term success groups were significantly higher than those of the long-term failure groups (p<.05) (Table 11).

Insulin resistance and, to a lesser extent, the reduced secretion of insulin are known to be the central pathogenic mechanisms of NIDDM.^8–13) These patients seldom develop ketosis, even in the absence of insulin therapy and are not dependent on exogenous insulin for immediate survival. In view of this, the addition of a program of regular exercise to dietary restriction and weight reduction could be an integral part of the treatment of NIDDM.¹⁴⁾

A strict caloric restriction could result in weight reduction, improved insulin secretion, improved insulin binding to receptor, decreased insulin resistance, and/or improved glucagon secretion. The dietary regimens employed consisted of 800–2,300Kcal/day for from 4 weeks to 6 months.^15–18) In addition to the attention given total caloric intake, a great deal of attention was given to the individual components comprising the diabetic diet. Previous attempts to restrict total CHO intake are no longer deemed advisable. Most authorities now advocate liberalization of CHO intake from 50 to 55% of the total calories.¹⁹⁾ Also, dietary fiber can reduce glycemic excursions and diminish insulin secretion. This is thought to be due to delayed gastric emptying and overall slowing of the rate of CHO digestion and absorption. In our studies, all subjects were given dietary regimens which included 50% CHO.

Exercise is commonly recommended in the treatment of NIDDM as a means of increasing energy expenditure and insulin sensitivity. Body fat loss, a sense of well-being, increases in aerobic capacity, increases in HDL-cholesterol level and adipocyte lipolysis, and decreases in blood pressure in hypertensive patients, psychologic stress and plasma triglyceride are also benefits which can be reaped from exercise.²⁰⁾ The general guidelines for aerobic conditioning are to exercise 3–5 days per week for 15–60 min per exercise session at a work intensity corresponding to 50–85% maximal oxygen consumption, or 60–90% of maximal heart rate reserve.^21,22) The specific kind, amount and duration of exercise should be selected according to physical condition of the individual.²³⁾ Patients with advanced complications were excluded from our study because of the possibility that microangiopathic complications might be aggravated.²⁴⁾ The amount of exercise in our regimen was greater than those in others.^25,26) Glycemic control was achieved in about 70% of patients. The glycemic control by exercise might be the result of the increase of glycogen repletion in the muscles. The improvement of the peripheral sensitivity to insulin might be due to increased non-oxidative glucose disposal in muscle tissue.^14,26–29) The results of glycemic control in non-obese NIDDM on long-term follow-up study can partially be explained by the lesser energy expenditure during exercise than in obese NIDDM.

In this study, the induction group achieved glycemic control with oral gliquidone for about 5 days (induction therapy). Several studies have revealed that a short-term program of insulin therapy improved blood sugar level or glucose homeostasis, insulin secretion, post-receptor defect and basal hepatic glucose production.^30–33) These results indicate that the restoration to normal of or improvement of hyperglycemia itself may induce the improvement in the post-receptor defect.

Several factors might be related to the glycemic control. In our study, the glycemic control was significantly related to the previous history of oral hypoglycemic agents, the duration of DM or the extent of diabetic complications, but not to the initial body weight, or FBS or HbA_1c levels. Turkington et al.³⁴⁾ reported that patients previously treated with oral hypoglycemic agents or insulin responded poorly to the dietary therapy, as our patients did. Nagulesparan et al.³⁵⁾ and Garvey et al.³³⁾ reported that the longer the duration of DM, which is commonly associated with advanced diabetic complications, the poorer the response to therapy. In our study, the patient with a shorter duration of disease (5 years or less) and lesser diabetic complications were better controlled than those with a longer duration of disease and more complications.

It was suggested that patients with a higher capacity of insulin secretion responded better to diet and exercise therapy.^34,36,37) In our study, the peak C-peptide levels were significantly higher in the long-term success group than in the long-term failure group.

In this study, weight loss in the success groups was slightly, but not significantly, greater than that in the failure groups. The addition of a program of strict weight reduction by dietary restriction and exercise may be needed to establish the proper guidelines for diabetic control. Such a program will bring an added benefit from the educational standpoint, in the form of better compliance and better glycemic control.