Exercise and Time of Day in Type 2 Diabetes

Overview

The overall purpose of the study is to test the effect of Noom on exercise and diet advice in adults with type 2 diabetes. The overarching hypothesis is that the use of Noom may promote better dietary adherence during an exercise program, thereby promoting greater weight loss and cardiometabolic health compared to lifestyle advice only. In particular, the investigators anticipate that changes in metabolic and vascular insulin sensitivity will correlate with glycemic control and blood pressure changes.

Type 2 diabetes (T2D) is associated with a 3-fold cardiovascular disease (CVD) mortality risk compared with healthy controls, and it is estimated that 30 million adults in the United States have the disease. In recent years the American Diabetes Association (ADA) and American College of Sports Medicine (ACSM) recommend moderate intensity (40-60% heart rate max, HRmax) aerobic exercise 3-5d/wk for the management of T2D. The statement also recognized that higher exercise intensity (\>60% HRmax) predicts better blood glucose control than exercise volume. Cardiovascular health (e.g. fitness, blood pressure, etc.) also appears to respond in an exercise dose dependent manner. Despite these suggestions, many people exercising compensate by eating calories back from exercise, thereby negating weight loss. Moreover, compliance and adherence to exercise and diet medical counsel is disappointingly low. Recent work has begun to target the best time of day to exercise in effort to improve weight loss and related health. This has evolved in part since circadian biology reveals people tend to become glucose intolerant, and develop insulin resistance and endothelial dysfunction in the evening compared with morning. As a result, it would be reasonable to hypothesize that exercise in the afternoon may be best at combating natural declines in health as well as optimizing training adaptations. However, not all studies agree that afternoon is the best time to exercise. In fact, some have demonstrated that 12 wks of aerobic plus resistance exercise improved glycemic control whether performed in the morning or afternoon in adults with T2D. Moreover, consistent morning exercise has been suggested to improve exercise adherence through possible enjoyment as well as lead to greater weight loss. Taken together, additional work is warranted to understand time of day in which exercise is performed given circadian influence may contribute to variations in favorable metabolic as well as vascular adaptation for CVD prevention/treatment. Excitingly, we have preliminary data showing that afternoon exercise induces greater weight loss, reductions in food intake as well as perceptions of appetite and increased insulin sensitivity when compared to morning exercisers. Thus, the overall purpose of this proposal is to determine whether exercise time of day differentially enhances likelihood of weight loss via appetite regulation as well as glycemic control. Our overarching hypothesis is that afternoon exercise will enhance the effectiveness of exercise to induce weight loss, improve appetite and improve glycemic regulation compared to exercise in the morning. Taken together, findings from this study will inform public health recommendations to contemporary behavioral strategies to treat T2D. The study will also provide much needed experimental evidence to time of day in which exercise is performed influences public health risk.