Exercising Toward Diabetes Control
More than 14 million Americans have type 2 diabetes,
a condition characterized by poor control of blood sugar, or
glucose (the body's principal source of energy). Type 2 diabetes
usually appears after age 40. However, more people are developing
the condition at an early age, and its overall incidence is rising.
A major culprit is excess weight due to inactivity and a poor
diet. Being overweight may impair the body's response to insulin,
the hormone that regulates glucose metabolism. Excess weight
also taxes the heart, which is adversely affected by diabetes.
Thus, exercise and a healthy diet are the first
treatments recommended for type 2 diabetes. Regular exercise
can decrease blood glucose levels and increase the body's sensitivity
to insulin. Exercise also protects the heart by reducing blood
pressure and triglyceride levels (a type of blood fat, or lipid).
Improved blood glucose levels can delay or reduce the need for
glucose-control medications and prevent diabetes-related complications,
such as heart and kidney disease, diabetic retinopathy (damage
to the light-sensitive portion of the eye), and diabetic peripheral
neuropathy (degeneration of nerves serving the legs and arms).
Yet few people with diabetes meet the U.S. Surgeon
General's minimum exercise recommendations for all adults: some
combination of activities such as walking, jogging, swimming,
and active chores (such as mowing the lawn or vacuuming) for
at least 30 minutes almost every day. In fact, one recent survey
of diabetes patients found that the majority of respondents did
not exercise at all. Exercise is beneficial for virtually everyone
with diabetes. However, special precautions are necessary, especially
for people who require certain glucose-control medications and
those with peripheral neuropathy.
Exercise increases vulnerability to two major diabetes-related
problems: hypoglycemia (a precipitous drop in blood glucose)
and foot sores. Hypoglycemia is initially characterized by sweating,
hunger, dizziness, anxiety, a rapid heart rate, and tremor. Without
proper attention, the sufferer may lose consciousness and go
into shock. Foot sores that are not properly treated can rapidly
worsen, sometimes within a matter of hours, and lead to infection.
Severe cases may require amputation.
Hypoglycemia is more common in patients who require
insulin or sulfonylurea medications such as glimepiride (Amaryl),
glipizide (Glucotrol), and glyburide (DiaBeta, Micronase). Those
on newer diabetes medicationssuch as metformin (Glucophage),
rosiglitazone (Avandia), or pioglitazone (Actos)are less
susceptible to the problem. The risk of foot sores is greater
in people with peripheral neuropathy, which decreases sensitivity
to foot pain. Poor circulation to the extremities, which impairs
healing, often compounds the problem.
Other exercise-induced complications include dehydration
and ketoacidosis (the buildup of waste products from fat metabolism),
and possibly retinal detachment. Dehydration may develop during
prolonged workouts because of excessively high glucose levels
(hyperglycemia) when diabetes is poorly controlled. A serious
condition, ketoacidosis is primarily a concern for people with
type 1 diabetes, which usually develops in youth and always requires
insulin. Some experts caution that retinal detachment may be
a risk when those with advanced retinopathy perform activities
that require bursts of strength. However, the data are unclear.
A Safe Routine
With proper planning, most diabetes patients can
exercise as much as they wish. "Become familiar with how
your blood glucose responds to various forms of exercise by assessing
your blood glucose before and after exercise, and every half
hour during workouts, and work with your health care team to
adjust your medical and exercise regimens accordingly," advises
Dr. Joel Braunstein, a Johns Hopkins cardiology fellow with a
special interest in diabetes.
Some standard practices prior to exercising will
help your routine go smoothly. One to two hours before working
out, have a meal and about a pint of water. Just before exercising,
check your blood glucose. If it is below 100 mg/dL, have a snack
containing 15 to 30 g of carbohydrates. If it is more than 250
mg/dL (for type 2 diabetes) or 200 mg/dL (for type 1 diabetes),
postpone exercising until the level declines. It's also important
to drink 8 to 16 oz of water every 30 minutes during your workout
and to replenish spent glucose with a post-exercise snack. Prolonged
workouts may require more frequent monitoring and brief breaks
for snacks and water. If you experience hypoglycemic symptoms
during your routine, rest and have a snack or some juice.
People with advanced diabetic neuropathy should
choose low-impact activities like swimming and cycling rather
than high-impact ones like jogging. Everyone with diabetes, and
especially those with peripheral neuropathy, should also inspect
the feet for signs of irritation before and after exercise. For
strength training, people with diabetic retinopathy should use
light weights and multiple repetitions as a precaution. People
with uncontrolled diabetes should not exercise until their blood
glucose levels stabilize and they meet the goals they establish
with their doctors.
From The Johns
Hopkins Medical Letter: Health After 50, August 2000.