Research Profile

Treatment for gestational diabetes begins with medical nutrition therapy, physical activity (PA), and, depending on pre-gestational weight class, weight management (i.e., lifestyle behavioral counseling). However, there is currently limited information to support the promotion of PA in clinical encounters. Our research program attempts to fill in this gap through the development of a specific PA prescription to support behavioral counseling for PA in the clinical setting, at the level of detail currently available to guide medical nutrition therapy (e.g., numeric targets for grams of carbohydrate per meal to guide meal planning). Our specific PA prescription for individuals with pregnancy hyperglycemia is to walk or ‘step’, ideally every day, for at least 30 minutes, at a cadence of at least 100 steps per minute. The element missing from our prescription is the best time of day for PA. Current recommendations do not address the optimal timing of PA, though there are several purported benefits to leveraging the time of day PA is performed. To the best of our knowledge, this will be the first randomized crossover trial to examine the effects of the timing of PA on the 24-hour glucose cycle in pregnant individuals at high risk for adverse pregnancy outcomes and the development diabetes later in life. Given the barriers to PA faced by this population, that timing is specifically considered for other treatments recommended for the condition (e.g., meal planning, insulin), and emerging evidence suggesting that afternoon/evening PA may positively affect glucose across the 24-hr cycle, increased scientific understanding of how one might potentially leverage the timing of PA to maximize health benefits is of interest.

Hyperglycemia in pregnancy increases the risk of maternal high blood pressure, cesarean delivery, delivering a large for gestational age infant, low blood sugar in the neonate, and abnormal glucose metabolism during childhood in the offspring. Elevated pregnancy glucose also increases the risk of maternal diabetes in the years following delivery. Physical activity (PA) reduces pregnancy glucose levels and the need for insulin in those with gestational diabetes, thereby reducing the risk of adverse perinatal outcomes and mitigating the risk of diabetes later in life. Unfortunately, most pregnant individuals in the United States do not meet PA recommendations, including those with pregnancies affected by gestational diabetes (GDM) or gestational glucose intolerance (GGI), who stand to benefit the most from PA in late pregnancy. There are several purported benefits to leveraging the time of day that PA is performed. Behaviorally, performing PA at the same time each day, particularly in the morning, seems to help with adherence. PA timing may impact metabolism by effecting appetite, eating behaviors, and sleep, as well as physiological processes beyond PA-related increases in energy expenditure, including greater fat oxidation and various circadian influences. Emerging evidence (primarily among men) also suggests that PA performed later in the day may be more efficacious than early PA for improving 24-hour glucose levels. This trial’s findings will allow the research team to further customize their specific PA prescription for GDM or GGI, and lead to a future randomized controlled trial of our refined PA prescription in an effort to support clinical behavioral counseling and ultimately increase PA in this population.

Animal evidence suggests that maternal exercise improves later life metabolic health in the offspring. The offspring of individuals with gestational glucose intolerance (GGI) or gestational diabetes mellitus (GDM) have an increased risk for obesity and diabetes, thus PA may be particularly beneficial for these pregnancies. Although maternal PA is indicated as treatment for GDM, PA levels tend to be sub-optimal and decline with the progression of pregnancy (although improvements in diet are typically observed). Attempts to increase PA levels in pregnant individuals with GGI or GDM run into a common barrier: time, when can the patient find time or negotiate for time for PA, given their busy schedule. Due to the busy lives and competing interests to PA faced by this population, increased scientific understanding of how one might potentially leverage the timing of their PA is of great interest. Medical nutrition and insulin therapy for GDM are already individualized in regards to timing. With increased scientific understanding, the timing of PA may be similarly leveraged (or rightfully ignored) by future behavioral interventions that aim to increase PA levels in this population.

We now have the technology needed to obtain reliable, timestamped measurements of glucose and physical activity (PA)/sleep across the 24-hour cycle for sufficiently sized samples of research participants. The future of diabetes research will leverage these exciting new technologies to better understand how lifestyle behaviors and their timing may influence health outcomes in people with or at risk for diabetes, as well as how lifestyle behaviors and their timing may be leveraged to maximize the efficacy of pharmacological therapies for people with diabetes.