The arrival of summer brings to mind visions of people having fun in the sun and recreating on the beach, but hotter weather also creates greater risks related to dehydration and heat stress for people who are physically active outdoors. Aging by itself negatively affects the body’s ability to dissipate heat in both dry and humid environments (1), but having diabetes further increases the risk of developing heat stress during outdoor activities, especially when it’s hot and/or humid (2). Whole-body heat loss may be impaired due to abnormal skin circulation and decreased sweating (3), both of which can lead to increases in body temperature and heart rate.
People with type 1 diabetes (4) and type 2 diabetes (5) may have impaired regulation of body heat. In particular, athletes with type 1 diabetes may sweat less, especially when they are working out at more intense levels (4), and many adults with type 2 diabetes have a reduced ability to be active in the heat. The good news, though, is that these individuals with diabetes can still acclimate to doing aerobic or resistance training in hotter environments.
What do people need to do to acclimate? Adequate hydration is key to maintaining blood volume and blood flow, both of which affect body cooling during physical activities. Overheating in any environment occurs more easily when dehydrated (6). Dehydration leading to less sweating is more likely when glucose levels are elevated and can lead to chronic hyperglycemia (5). So, everyone needs to closely monitor and manage blood glucose during training or competition in the heat to avoid making any existing impairments in the ability to cool the body worse.
Plain water is usually effective for hydrating during activities lasting an hour or less. During longer workouts or events, water can also suffice for hydration, but sports drinks or other fluids may provide extra carbohydrate to keep blood glucose from dropping too much. In general, consuming about 1 liter of fluid per hour during activities in the heat is recommended (7)—but don’t take in too much or water intoxication can result. Hydrate after activities to restore fluids, replace electrolytes lost through sweat and breathing (8), and manage blood glucose.
Do the following to minimize the risk for exercise-related heat stress:
Avoid exercising during the hottest times of the day; choose morning or evening times
Stay out of direct sunlight during exercise whenever possible
Wear loose-fitting, light-colored exercise clothing
Take in extra fluid and electrolytes (e.g., salt) every day while acclimating
Don't wait until you're thirsty to drink fluids, and avoid alcohol since it’s dehydrating
Give yourself a couple of weeks to fully acclimatize to exercising in the heat
Try to stay cool until you start exercising, or exercise indoors
During hot-weather exercise, watch for signs and symptoms of heat-related illness
If unfit or new to exercise, be extra cautious when working out in the heat
References:
1. Notley SR, Poirier MP, Hardcastle SG, et al. Aging Impairs Whole-Body Heat Loss in Women under Both Dry and Humid Heat Stress. Med Sci Sports Exerc. 2017;49(11):2324-32.
2. Poirier MP, Notley SR, Boulay P, et al. Type 2 diabetes does not exacerbate body heat storage in older adults during brief, extreme passive heat exposure. Temperature. 2020;7(3):263-9.
3. Notley SR, Poirier MP, Sigal RJ, et al. Exercise Heat Stress in Patients with and without Type 2 Diabetes. JAMA. 2019;322(14):1409-11.
4. Carter MR, McGinn R, Barrera-Ramirez J, et al. Impairments in local heat loss in type 1 diabetes during exercise in the heat. Med Sci Sports Exerc. 2014;46(12):2224-33.
5. Kenny GP, Stapleton JM, Yardley JE, et al. Older adults with type 2 diabetes store more heat during exercise. Med Sci Sports Exerc. 2013;45(10):1906-14.
6. Colberg SR. Nutrition and Exercise Performance in Adults with Type 1 Diabetes. Can J Diabetes. 2020;44(8):750-8.
7. Yardley JE, Colberg SR. Update on Management of Type 1 Diabetes and Type 2 Diabetes in Athletes. Curr Sports Med Rep. 2017;16(1):38-44.
8. Evans GH, James LJ, Shirreffs SM, Maughan RJ. Optimizing the restoration and maintenance of fluid balance after exercise-induced dehydration. J Appl Physiol. 2017;122(4):945-51.