Spotlight on exercise

Two recent studies analyzed the effects of exercise on glycemic control in patients with type 2 diabetes or impaired glucose tolerance.

In the first study, published by JAMA Internal Medicine on July 1, 105 overweight or obese older patients (mean age, 61) with impaired glucose tolerance or type 2 diabetes had aerobic exercise training for 12 to 16 weeks. On average, the patients lost weight and improved their body composition, aerobic fitness, fasting plasma glucose and two-hour oral glucose tolerance test (OGTT) levels. However, patients with OGTT levels of 236 mg/dL or higher at the start of the study showed less improvement in their OGTT by the end. Patients who started with a hemoglobin A1c (HbA1c) above 6.2% also saw less improvement in their HbA1c and aerobic fitness from the exercise, leading the study authors to conclude that patients with chronic hyperglycemia may not respond as well to exercise, so using exercise to treat poorly controlled diabetes may have limited chances of success.

The other study, published by Diabetes Care on June 11, included 10 inactive adults, age 60 or over, with fasting blood glucose concentrations between 105 and 125 mg/dL, who were studied for multiple 48-hour periods. They spent the first day being inactive as a control period and then the next day walked for 45 minutes at either 10:30 a.m. or 4:30 p.m. or took a 15-minute walk half an hour after each meal. The morning walk and the post-meal walking both improved 24-hour glucose control, but the post-meal walks were most effective at lowering the glucose concentration measured three hours after dinner. The researchers concluded that the timing of exercise may be as important as volume and intensity and speculated that shorter bouts may be better tolerated by older patients, who could even incorporate this exercise into common daily activities, such as dog walking.