Dietary Management

The basal insulin requirement is high during the early morning hours; is relatively stable during the daytime hours; declines in the middle of the night, when hormones achieve their nadir; then rises again. Considering that basal insulin constitutes 50% of the total daily requirement, as detailed in Figure 4, the hourly basal rates for an insulin infusion would be 50% less than the basal dose when insulin declines between midnight and 4 AM, 50% more in the early morning hours between 4 AM and 10 AM, and the same (ie, 50% of the total daily insulin requirement) during the day (from 10 AM to midnight).
Fig. 4

To achieve the proper balance of diet among the 4 variables that influence the control of diabetes, it is important to appreciate that caloric requirements vary with age (Figure 5) and patient type (Table 3). Whereas dietary protein is the major determinant of basal insulin levels, CHO is the major determinant of blood glucose levels, and peak postprandial response is directly related to the CHO content of a meal. Postprandial hyperglycemia is a recognized risk factor for coronary heart disease in persons without diabetes6; it has also been linked to neonatal hypoglycemia, macrosomia, and the need for cesarean delivery among women with gestational diabetes.7 Therefore, it is critically important for patients with diabetes to learn how to estimate the amount of CHO consumed at each meal and determine meal-related insulin requirements accurately to prevent postprandial hyperglycemia (Figure 6). Total CHO intake should be limited to 25% of the meal plan.8 The diabetes exchange system for meal planning was recently revised to permit a more accurate estimate of CHO consumption. This simplifies meal planning and enables more precise estimation of premeal insulin doses. For insulin to be matched with food, the CHO content of the food must be assessed in grams.9 Values are obtained from food lists (CHO counters) and product nutrition labels.

Figure 5. Caloric requirements by age.
Patient Type Calories x Weight (kg body weight for maintenance)*
Boys (puberty) 70 kcal/kg
Girls (puberty) 60 kcal/kg
Men 28-35 kcal/kg
Women 20-25 kcal/kg
Pregnant women 30 kcal/kg

*For persons who are not overweight. Values at the upper end of the range indicate the level for active persons.

Table 3. Daily caloric requirements by patient type

Figure 6. Formula for calculating meal-related insulin dose.

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