Nutrition

Exercise and Diabetes

Benefits from exercise include weight control; improved blood pressure, cholesterol, and blood glucose; and a sense of well being that can also improve your stress management and sleeping habits. The American Diabetes Association recommends gradually increasing the duration and frequency of exercise to 30-45 minutes of moderate aerobic activity a day, 3-5 days a week, when possible.

Exercise over extended periods of time requires carbohydrate intake as a source of fuel (blood glucose). Part of this requirement is met by stored glucose in the muscle (glycogen). Depletion of muscle glycogen over a period of 60-90 minutes of aerobic exercise can lead to fatigue. Lower intensity exercise over a longer period of time requires available blood glucose as an additional source of fuel. Hypoglycemia may occur after about 90 minutes (or sooner) of exercise when both muscle and liver glycogen stores are depleted and up to 24-36 hours later.

It is important before beginning lengthy exercise to plan for it , if you are taking insulin, you will need less of it and/or you can compensate with extra carbohydrate intake. Too much carbohydrate or food intake can lead to weight gain. Insulin or carbohydrate adjustments prior to, during, or after exercise can depend on many factors: intensity, duration, usual insulin regimen, and blood glucose patterns. Monitoring your blood glucose for these patterns can identify what type and how much carbohydrate you need.

The time of day that you exercise can make a difference . In the morning upon waking, when cortisol levels are high and insulin levels are low, you are less likely to experience low blood glucose when exercising. A balance of hormones is thus important for exercise. If there is too little insulin, blood glucose levels and ketone production can rise. During exercise, epinephrine increases fatty acid mobilization and muscle glycogen breakdown, and glucagon causes the liver to produce glucose. Balance is the key, it is more important to be consistent in your exercise program rather than to only exercise in the morning.

If you have type 1 diabetes , it is recommended to not exercise if your blood glucose is over 250 and ketones are present and to use caution if blood glucose is over 300 and no ketones are present.

If you have type 2 diabetes , and your blood glucose is over 150, you may not need carbohydrate for moderate intensity and duration.

Generally, for 30 minutes of intense exercise, 15-30 g of carbohydrate (fruit, yogurt; ½-1 sandwich; peanut butter with crackers, etc) may be needed pre exercise ; however, experienced athletes may choose less or more depending upon the duration, their usual regimen of insulin, and blood glucose patterns. For up to 60 minutes of exercise, cool water is recommended. But for 60-90 minutes, water and carbohydrate will be needed (diluted fruit juice or some sports drinks may be used). It usually takes the body about 24 hours after exercise to replenish lost fluid. It has been suggested to drink 16 oz of water an hour prior to exercise, 8 oz 15 minutes before, and 4-6 oz every 15-20 minutes during exercise. Drink water before, during, and after exercise.

Insulin and carbohydrate recommendations for cycling (for insulin pump):

-If cycling for less than 1 hour, consider reducing the basal rate by 25-50% about 1½ hours before the exercise. If cycling in the am, less carbohydrate supplementation may be needed due to higher insulin resistance in the am.

-If cycling for 1-4 hours, reduce pre meal or bolus insulin by 30-50% at meals before and after the cycling, depending upon any basal rate reductions and food intake.

-A general rule is to consume about 15-30 g of carbohydrate for every ½ to 1 hour of cycling, depending upon the intensity. For longer duration of cycling, consider additional carbohydrate intake afterwards.

-For longer duration, consider reducing basal rates 30-60 minutes prior to cycling and even continuing several hours or overnight to avoid hypoglycemia. A bedtime snack may be needed. Basal rates can be reduced by 50% for 12-24 hours depending upon intensity, duration, and type of exercise.

Other considerations are temperature and altitude . Heat, cold, and higher altitudes all may cause hypoglycemia. Monitor your blood glucose.

The expression used by scuba divers, “Plan your dive and dive your plan”, can also be applied to exercising with diabetes: “Plan your exercise and exercise your plan”. When monitoring your blood glucose, know what you will do with the results.

It is our intention that this information will enable you to make better decisions when exercising regarding identifying blood glucose patterns and making any needed adjustments in food intake or insulin administration.

References:

Colberg, Sheri. (2001). The Diabetic Athlete. Illinois : Human Kinetics.

American Diabetes Association. (2006). Clinical Practice Recommendations. Diabetes Care , 29, Supplement 1.

With additional contributions by:

Rick Philbin, MED, ATC, CSCS

National Board Member: Diabetes, Exercise & Sports Association

National Presenter: “Children with Diabetes”

Northeast Regional Manager, Animas Corporation

Katie Conschafter, MS, RD, LDN, CDE

Clinical Manager, Virginia, Animas Corporation

Copyright 2006 Eastern Virginia Medical School/The Strelitz Diabetes Institutes. All Rights Reserved.