Fueling the Athlete with Diabetes
Whether an athlete is a weekend warrior or an elite marathoner there are some fundamental nutrition constructs that have been shown to improve athletic performance. In general, the following statements are true for all athletes, including athletes with diabetes:
- Exercise intensity and endurance directly related to hydration status and the availability of carbohydrate in the forms of muscle glycogen, liver glycogen and blood glucose.
- Athletes need more dietary carbohydrate, dietary protein and total calories than their sedentary counterparts.
Adding type 1 diabetes or type 2 diabetes using insulin to the mix alters fueling strategy a bit, and definitely creates challenges that athletes not using insulin don’t have to face. What follows is a brief review of pre, during and post exercise fueling strategies that should help an athlete with diabetes perform to the best of his or her capabilities.
Fluid/Hydration
How the body cools itself during activity…
- Blood carries heat from core to below skin
- Evaporating sweat cools blood under skin
How dehydration works…
- Blood volume decreases making more difficult to move heat from core to just below skin
- Decreased blood volume = decreased sweat rate in order to preserve body fluid leading to vicious circle of overheating
- For every 1% body weight loss heart rate increases by 5-8 beats per minute and core temp increases 0.4-0.5 degrees Fahrenheit
The good news…
- Proper hydration allows an athlete to last 33% longer compared to an athlete who doesn’t drink during a workout
Hydrating before exercise
- At least 4 hours before exercise drink 5-7 ml/kg of body weight
- Two hours before exercise drink 3-5 ml/kg of body weight
- For a 180 pound athlete this would be 14-19 oz four hours before and 8-14 oz two hours before exercise
Hydrating during exercise
My inclination is to knock Gatorade because it has become such a dominant company. However, when it comes to hydration during exercise there probably isn’t a better option than good old original Gatorade.
- If the event or practice will last an hour or more a beverage containing 6-8% carbohydrate is recommended to help maintain blood glucose during the activity. Original Gatorade is a 6% carbohydrate solution.
- Including sodium in a rehydration beverage is helpful because sodium draws fluids into the body and helps to stimulate the thirst drive encouraging fluid consumption.
It would be great to make a blanket recommendation that all athletes should drink “x” amount of fluid during exercise, but there are entirely too many variables that influence sweat rate and hydration needs (i.e. - body size, temperature and relative humidity, degree of heat acclimation, etc.). The American College of Sports Medicine recommends monitoring body weight changes during normal training conditions in order to come up with a customized fluid replacement strategy.
To put hydration during exercise into a bit more concrete terms it is recommended that marathoners drink from 0.4-0.8 liters (13-27 oz) of fluid each hour while training or competing.
Hydrating after exercise
- Drinking at least 16-24 oz of fluid for every pound of body weight lost during exercise should help the athlete to rehydrate properly after training or competing.
- Consuming a rehydration beverage containing sodium and/or salty foods at meals and snacks will assist with replacing fluid lost with exercise.
Carbohydrate
Depending upon the activity and training duration, recommended carbohydrate intake for athletes ranges from 6 to 10 grams of carbohydrate per Kg of body. Going back to our 180# athlete, he should try to consume 490-818 grams of carbohydrate per day. Even at the lower end of this scale this amount of carbohydrate may sound like blasphemy to someone with diabetes and to people who advise them.
The trick here is to provide enough dietary carbohydrate to restore glycogen after hard training without sacrificing blood glucose control. An interesting study done with athletes with type 1 diabetes looked at exercise performance on a 50% carbohydrate diet vs a 59% carbohydrate diet consumed for three weeks at a time. While on the higher carb diet the athletes experienced increased insulin requirements, decreased muscle glycogen, deterioration of glycemic control and reduced exercise performance.
The bottom line for the athlete with diabetes? Teach the to consume a diet that is about 50% carbohydrate and encourage close blood glucose monitoring.
Carbohydrate intake before exercise
Eating before exercise has been shown to improve athletic performance. The meal prior to competition should be low in fat and provide enough carbohydrate and calories to prevent hunger. Of course the athlete with diabetes will want to make sure that blood glucose is not too high or too low going into competition.
Carbohydrate during exercise
Endurance and stop and go (e.g. - soccer, basketball) athletes benefit from consuming carbohydrate during exercise. A general recommendation is to consume 30-60 grams of carbohydrate per hour of activity. Depending upon the event and the athlete’s preference this carbohydrate can come in the form of sports drinks, carbohydrate gels and “goos” or food. I am a proponent of athletes using sports drinks to rehydrate because they also provide a source of carbohydrate during exercise. Drinking 8 oz of Gatorade every 15 minutes during exercise provides 56 grams of carb per hour.
Carbohydrate after exercise
The purpose of consuming carbohydrate after exercise is to replenish glycogen as quickly as possible. Ideally, begin taking in carbohydrate within 30 minutes of completing practice or competition in the amount of 1.0-1.5 grams per Kg. Consuming this amount of carbohydrate should be repeated every two hours for up to six hours post exercise to help replete dissipated glycogen reserves.
Again, the challenge associated with the athlete using insulin is maintaining good glycemic control while repleting liver and muscle glycogen post exercise. As you approach this keep in mind that for 30-60 minutes post exercise, muscle tissue is able to take up glucose without assistance from insulin. Accordingly, during the 1st hour post exercise exogenous insulin may not be necessary to “cover” the carbs ingested. Finally, working on glycogen repletion immediately after exercise will help to reduce the risk of the post-exercise hypoglycemia that many athletes experience later in the day following a hard workout.
Protein
Dietary protein is needed by athletes for muscle repair and maintenance on a daily basis. Recommended protein intake for strength and endurance athletes ranges from 1.2-1.7 gm/Kg. Contrary to the practice of many strength athletes, the maximum daily utilization of dietary protein is 2.0-2.5 grams per Kg. Additionally, the maximum amount of dietary protein that can be utilized at any one time is about 20 grams.
Protein before exercise
With resistance exercise consuming 6 grams of protein plus 35 grams of carbohydrate immediately before training resulted in increased protein synthesis when compared to the same combination being consumed after exercise. A simple, practical application of this principle would be to have the athlete consume a 1 cup of low-fat fruit yogurt containing 40 grams of carb and 8 grams of protein prior to a strength workout.
Protein during exercise
Although it is known that certain amino acids are utilized for energy when the body’s carbohydrate stores get low, there is no literature that supports using supplemental sources of protein or amino acids during exercise.
Protein after exercise
A recovery snack containing both carbohydrate and protein post-exercise is an ideal anabolic mixture that will prevent muscle breakdown and stimulate repair. A very popular and effective recovery snack utilized by many athletes is chocolate milk. One cup of non-fat chocolate milk = 26 grams of carb and 11 grams of protein.
Fat
There is not a lot to say about fat and exercise other than healthy unsaturated fats (nuts, oils, avocados, etc.) are a great way to replace calories burned with exercise. Once the athlete’s carb and protein needs have been met, put dietary fat to work to boost calorie intake without the worry of blood glucose elevation that comes with increased carbohydrate consumption.
Fat before exercise
- Dietary fat delays gastric emptying and can make an athlete feel full and uncomfortable during practice or competition
- To allow ample time for digestion dietary fat should be consumed at least 4 hours before competition
Fat during exercise
- Unless we are talking about a super ultra endurance event like one of those 100 mile runs, fat really has no role during exercise
- Please see bullet number 1 under “fat before exercise”
Fat after exercise
- Once meeting initial post-exercise carb and protein needs has been initiated, consuming fat can commence!
References:
- American College of Sports Medicine. Exercise and fluid replacement position stand. Medicine & Science in Sports & Exercise, 39 (2) 377-390.
- American Dietetic Association, American College of Sports Medicine, Dietitians of Canada. Nutrition and athletic performance joint position statement. Journal of the American Dietetic Association, 109: 509-527, 2009.
- Colberg, S. Diabetic Athlete’s Handbook. Human Kinetics, Champaign, IL, 2009.
- McKewen, M W, et al. Glycaemic control, muscle glycogen and exercise performance in IDDM athletes on diets of varying carbohydrate content. International Journal of Sports Medicine, 20 (6): 349-353, 1999.
- Skolnik H & Chernus, A. Nutrient Timing for Peak Performance. Human Kinetics, Champaign, IL, 2010.