Nutrition and Exercise for Patients with Diabetes Mellitus

December 2013, Vol 1, No 2 - Inside Cardiometabolic: Diabetes
Todd Paulsen, PharmD, CDE, BCPS

There is confusion within the general population about which is the healthiest and most effective dietary regimen. Many “fad” diets—such as low-fat or high-protein—are promoted to cause abnormally large weight reductions, but the reality is that weight frequently returns without the proper amount of exercise. The concern is compounded for patients with diabetes, because some dietary changes may actually be detrimental. In addition, there are considerations depending upon the patient’s weight, age, comorbidities, and type of diabetes. This section will summarize the current dietary recommendations balanced with exercise for patients with diabetes mellitus.

Visceral Fat and Diabetes

The accumulation of abdominal (visceral) fat is highly associated with the development of type 2 diabetes mellitus. Additional consequences of this centralized obesity pattern include hyperlipidemia, hypertension, cardiovascular disease, depression, osteoarthritis, and some types of cancer. The primary source of the problem is continuous insulin resistance.1,2

In normal human physiology, insulin resistance is a protective mechanism that preserves glucose for the brain during periods of starvation. In extended periods without food intake, the liver produces glucose. Insulin is not required for glucose to enter the brain. Peripheral tissues, such as fat or muscle, do require insulin for glucose uptake. During starvation, free fatty acids (FFAs) are released from visceral fat and provide energy for these tissues. The excess FFAs also cause insulin resistance and, in turn, peripheral tissues may not uptake glucose and preserve it for the brain.

In today’s modern lifestyle, humans are often storing excessive visceral fat. This leads to a constant release of FFAs into the bloodstream, causing continuous insulin resistance. To overcome this resistance, pancreatic beta-cells release excessive amounts of insulin. Ultimately, in susceptible individuals, the beta-cells “burn out” and die, leading to blood accumulation of glucose and symptoms of diabetes mellitus.

Lifestyle Modifications for Patients with Diabetes

To temper insulin resistance, lifestyle modifications that reduce excessive abdominal fat can have pronounced effects on the blood glucose levels of patients with diabetes mellitus, and may delay the onset of full-blown diabetes in individuals with prediabetes. The least invasive mechanism is to promote a healthy balance of reduced caloric intake in conjunction with moderate exercise.1-3

The American Diabetes Association (ADA) recom­mends individualized therapeutic lifestyle changes in patients with diabetes depending upon their needs. Those who are overweight can benefit from as little as a 5% to 10% reduction in body weight to reduce insulin resistance. If possible, this should be paired with an exercise program that achieves at least 150 minutes per week of moderate activity, including aerobic exercise, flexibility activities, and resistance training. No single dietary program is emphasized, so a reduction plan may include either low-carbohydrate, low-fat calorie-restricted, or Mediterranean-style diets for short-term weight loss for up to 2 years.1,3

Behavior modification with physical exercise and dietary changes together are important to maintain weight loss. Encouraging additional fiber is also recommended. Dietary fiber is minimally absorbed and provides a sense of “fullness.” The ADA endorses the US Department of Agriculture dietary recommendation of 14 g of fiber per 1000 calories. It is also recommended that individuals who are at risk for type 2 diabetes limit their intake of sugar-sweetened beverages.1

Carbohydrate monitoring is essential to regulating after-meal blood glucose levels and reaching glycemic goals. This can be achieved through carbohydrate counting, making proper dietary choices, or using carbohydrate exchange programs. This process may be confusing for the patient with diabetes and his or her family. For complex regimens, referral to a registered dietitian or nutritionist who is familiar with the components of medical nutritional therapy for patients with diabetes mellitus may be appropriate.

Patients with diabetes who select low-carbo­hydrate diets should be aware of the concerns associated with these diets and their impact on diabetes. These concerns include monitoring lipid profiles, renal function, and protein intake (particularly in those with nephropathy). Hypoglycemic therapy also may need to be adjusted. It is noted that the recommended daily allowance for digestible carbohydrates is 130 g daily; the long-term metabolic effects of daily intake lower than this is unknown.1

To reduce potential atherogenic lipid profiles—such as elevated low-density lipoprotein cholesterol—saturated fat intake should be reduced to <7% of the total daily calories consumed, along with a minimal intake of trans fat. Supplementation with antioxidants, such as vitamins C and E, are not recommended, because a long-term benefit has not been established. Alcohol may be consumed in moderation, with a daily maximum of a 1-drink equivalent in women or 2 in men. Large quantities of alcohol can inhibit glucose production and may lead to hypoglycemia.1

Insulin Regimens and the Patient with Type 1 Diabetes

In contrast to most patients with type 2 diabetes mellitus, type 1 diabetes often presents with weight loss because of the absolute lack of insulin. In addition, type 1 diabetes frequently presents during adolescence, so normal growth and proper nutrition are important considerations. Dietary and lifestyle modifications require even greater caution, as the patient with type 1 diabetes produces no insulin at all and often requires more complex insulin regimens.

Most patients with type 1 diabetes will be using insulin regimens that include basal and mealtime (prandial) injections 3 or more times daily, or they may be using continuous subcutaneous insulin infusion. This requires education on how to match prandial insulin doses with carbohydrates, premeal blood glucose levels, and anticipated physical activity. An understanding of carbohydrate quantities associated with each food item is essential and could impact the amount of insulin that is injected with a given meal.

A patient who is receiving a complex dosing regimen of insulin will learn how much glucose reduction occurs with the injection of 1 unit of insulin, taking the premeal blood glucose and the amount of carbohydrates they will be ingesting into consideration. Patients should know their insulin-to-carbohydrate ratio for meal dosing, as well as the amount of insulin needed as a correctional dose in relation to the premeal blood glucose.

In a hypothetical case, let’s assume that a patient’s insulin-to-carbohydrate ratio is 1 unit of insulin for each 15 g of carbohydrates with the meal. The patient is targeting a glucose level of <130 mg/dL before meals. For this case, we will calculate a 30-mg/dL reduction for each unit of insulin. For example, before lunch, the glucose level is 161 mg/dL and the meal contains 60 g of carbohydrates. The recommended dose would be 1 unit of correctional dose insulin plus 4 units to control the 60 g of carbohydrates consumed. Thus, 5 units of mealtime insulin will be given. Note that each patient’s requirements and goals are different, and initial therapy often requires estimates.

Special Concerns Related to Elderly Patients with Diabetes

It is important to understand that complex dietary and lifestyle changes may not be appropriate in elderly patients with diabetes. This is particularly true in the long-term care setting, where fall risk secondary to hypoglycemia can be an issue. It is also essential to remember that malnutrition can occur in this setting and, therefore, calorie restriction could be harmful. Balanced diets that provide appropriately portioned sizes are mostly recommended. The “diabetic diet” is no longer recognized as an appropriate physician order.4


Pharmacists must understand the complexity of the various lifestyle and dietary regimens and their impact on the patient with diabetes. General knowledge of basic concepts is important. Some pharmacists in clinical settings may be involved with the modification of lifestyle habits to fit an individual patient’s needs. Referring a patient with diabetes to a registered dietitian or nutritionist is also an option for those patients with greater glycemic control needs.


  1. American Diabetes Association. Standards of medical care in diabetes—2013. Diabetes Care. 2013;36(suppl 1):S11-S66.
  2. Handelsman Y, Mechanick JI, Blonde L, et al. American Association of Clinical Endocrinologists Medical Guidelines for Clinical Practice for developing a diabetes mellitus comprehensive care plan. Endocr Pract. 2011;17(suppl 2):1-53.
  3. Inzucchi SE, Bergenstal RM, Buse JB, et al. Management of hyperglycemia in type 2 diabetes: a patient-centered approach: position statement of the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD). Diabetes Care. 2012;35(6):1364-1379.
  4. American Medical Directors Association. Diabetes Management in the Long-Term Care Setting. Columbia, MD: American Medical Directors Association; 2008; revised 2010.
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Last modified: February 12, 2014
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