Continuing Education: Obesity and New-Onset Diabetes Mellitus

Article excerpt

The incidence of type 2 diabetes mellitus has, like that of obesity, increased significantly in the past decade and is reaching epidemic proportions in the developed world. Approximately 16 million people in the United States have type 2 diabetes, with 800,000 new cases diagnosed each year. This national figure is predicted to increase to 50 million in the next 30 years. Its incidence is steadily rising due to an aging population and to our limited success in controlling risk factors such as obesity and physical inactivity.

Obesity, in addition to being a major risk factor for the development of type 2 diabetes, makes the management of diabetes challenging and complex. Diabetes and obesity are linked to other metabolic aberrations, including hypertension, dyslipidemia, hyperglycemia, and hyperinsulinemia. The coexistence of these metabolic abnormalities is strongly associated with increasing risk of cardiovascular disease. The purpose of this paper is to discuss the management of type 2 diabetes in the obese patient and the role of the pharmacy practitioner in such patients.

What is type 2 diabetes?

This extraordinarily common, complicated, multifactorial disease affects approximately 6% of the United States population. In type 2 diabetes, multiple genes and multiple environmental factors interact, resulting ultimately in development of the diabetic state. Research has demonstrated that type 2 diabetes is strongly genetically determined, but different genetic factors may play a role in different populations or families. Likewise, based on genetics, certain racial and ethnic groups are at very high risk for development of type 2 diabetes-- but only if environmental factors allow or promote its expression. Obesity, physical inactivity, and other lifestyle factors have been identified as important environmental risk factors in genetically susceptible individuals. Figure 1 highlights these complex gene/environment interactions.

Type 2 diabetes is characterized by defects in both insulin secretion and insulin action. A resistance to insulin action in many different tissues in the body, coupled with an inability of the pancreas to deliver insulin in a precisely regulated pattern and quantity to control glucose metabolism, ultimately leads to high blood glucose levels and clinically overt type 2 diabetes.

The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus developed the current guidelines for the diagnosis of type 2 diabetes, as shown in Table 1. There are three ways to diagnose type 2 diabetes, all requiring confirmatory testing on subsequent days: a random plasma glucose of > 200 mg/dl; a fasting plasma glucose (FPG) of > 126 mg/dl; or a 2-hour oral glucose tolerance test with plasma glucose > 200 mg/dl. An FPG < 110 mg/dl is considered normal, while an FPG of > 110 mg/dl and < 126 mg/dl is defined as impaired glucose tolerance or impaired fasting glucose.

Although not the topic of this discussion, Type 1 diabetes results from immune-mediated destruction of the pancreatic beta cells.

What is meant by 'overweight' and 'obese'?

The recently published National Institutes of Health (NIH) Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults defines overweight as a body mass index (BMI) of 25 to 29.9 kg/m^sup 2^. Obesity is defined as an excess of total body fat demonstrated by a BMI of > 30 kg/m^sup 2^.

Several methods have been employed to assess body weight. Waist circumference, waist-to-hip ratio, and measures of skinfold thickness have been used to describe fat distribution. Hydrodensitometry, bioimpedance, computerized tomography, and magnetic resonance imaging have also been used to measure body-fat composition and distribution but are not practical clinically. The BMI is a useful estimate of body fat, regardless of age, race, or gender and correlates well with morbidity and mortality. …