Primary Care Update
Brief Summaries for Clinical Practice
Exercise Can Improve Glycemic Control:
How to Get Patients Started
CDC/Amanda Mills
JOHN WHYTE, MD, MPH
Silver Spring, Md
CHRISTOPHER MOHR, PhD, RD
Louisville, Ky
T
he prevalence of diabetes is increasing in epidemic proportions. Nearly
26 million people in the United
States currently have diabetes.1 Of those,
the disease has been diagnosed in approximately 18.8 million—and about 7
million have undiagnosed disease. Moreover, more than 1.9 million new cases
occur annually. An additional 79 million
people have prediabetes (defined as either
impaired fasting glucose, indicated by a
glucose level of 100 to 126 mg/dL after
an overnight fast, or as impaired glucose
tolerance, indicated by a glucose level of
140 to 199 mg/dL after a 2-hour oral
glucose tolerance test). The overwhelming majority of persons with diabetes—
nearly 90%—have type 2 diabetes.
THE BURDEN OF DIABETES
The healthcare cost of diabetes is
significant; according to the Centers for
Disease Control and Prevention, approximately $116 billion is spent on direct
medical costs, and another $58 billion is
spent on other costs associated with the
disease, such as missed days of work and
a subsequent loss in productivity.
Diabetes is associated with significant morbidity and mortality. Adults
Dr Whyte is a former medical advisor at the US
Department of Health and Human Services in
Washington, DC, and director of the Secretary’s
Council on Private Sector Initiatives. He is currently the chief medical expert and vice president,
health and medical education, at Discovery
Channel in Silver Spring, Md. Dr Mohr is a nutritionist and exercise physiologist and is co-owner
of Mohr Results, Inc. He is also a consulting
sports nutritionist for the Cincinnati Bengals.
www.Consultant360.com with diabetes are 2 to 4 times more likely
to have heart disease or stroke. Diabetes
is now considered a cardiac risk factor
equivalent—the excess risk of fatal coronary heart disease for patients with diabetes is nearly equivalent to those without diabetes who have had a previous
coronary event.2
OBESITY AND TYPE 2 DIABETES
The dramatic increase in type 2 diabetes is partly due to the increased prevalence of obesity. Most patients with diabetes are overweight.3 Moreover, adults
with diabetes are more than 3 times
more likely to be morbidly obese (body
mass index of more than 40) than adults
without diabetes and more than 1.5
times more likely to be obese (body mass
index of 30.0 to 39.9).
Since obesity is a function of energy
intake and output, it is important that
patients maintain a healthy diet and be
physically active. Obesity is partly related
to physical inactivity. As a result, increasing activity or exercise may decrease the
rising incidence of type 2 diabetes.
Until recently, many medical professionals believed that patients with diabetes should not engage in exercise proJanuary 2013 n consultant
45
Primary Care Update
Exercise Can Improve Glycemic Control
Sample 5-Day Walking Regimen for
Patients With Diabetes
I
nitiate your walking program according to the following schedule (Table 1),
devoting 5 days each week to the regimen. During the initial 12-week period,
you will increase your walking time by 10
minutes every 4 weeks until you reach the goal
Table 1 – Sample
of 40 minutes per bout of exercise.
walking regimen
If necessary, the walking sessions can be
divided into shorter exercise bouts; any aerobic
WeeksWalking
exercise bout lasting 10 minutes or longer
duration (min)
counts toward your total. You should remain
1-420
erect, taking full strides and swinging your
arms comfortably.
5-830
Before beginning a walking session, you
should perform stretching exercises (Table 2).
9-1240
Warm up for 5 minutes by walking or marching in place. Rest and stretch before a brisk
walk. Stretch each side 3 to 4 times, holding for 20 to 30 seconds. Do not
“bounce”—these are static stretches. Be sure to breathe regularly throughout each
of the stretches.
Walking burns approximately the same number of calories as jogging; each
mile of walking or jogging burns approximately 100 calories. Therefore, there is
no need to push yourself to jog unless that is what you desire.
Cool down by walking slowly for approximately 5 minutes and stretching
using the same stretches described above.
Table 2 – Stretching exercises
Stretching exercise
Description
Calf stretchPress your back heel to ground, keeping
the leg straight. Bend the front knee,
keeping both knees pointing forward.
Repeat with your back leg slightly bent.
Do this for both legs.
Hamstring stretchPlace one foot forward and straighten
the leg. Raise the toe of this foot so that
you are resting on the heel. Bend the
back knee and place both hands right
above the knee. Set your body back so that
the stretch is felt in the straightened leg.
Switch legs and repeat.
Quadriceps stretchPull your ankle to the buttocks with
the hand on the same side of your leg
(ie, the right hand pulls the right foot
and the left hand pulls the left foot).
Keep your body upright and the
knee pointing straight to the ground.
Keep the hips facing forward.
46
consultant n January 2013 grams, in view of the increased risk of
hypoglycemia that is associated with exercise, especially in persons with type 1
diabetes. When patients with diabetes
have inadequate insulin, there is an excessive release of counter-regulatory insulin hormones. Physical activity may increase already high levels of glucose and
ketone bodies and thereby precipitate
ketoacidosis. However, although there is
a risk of hypoglycemia, the benefits of
physical activity exceed that risk.
BENEFITS OF EXERCISE
In people with type 2 diabetes, exercise can improve peripheral insulin sensitivity as well as enhance insulin binding. Exercise also decreases abdominal
fat, reduces free fatty acids, and increases
insulin-sensitive skeletal muscle, which
may result in improved glycemic control.
Of note, it has been shown that these
improvements disappear a few days after
exercise is discontinued. Therefore, it is
imperative that patients realize that exercise is an activity they must incorporate
into their lives.
It has been demonstrated that patients with type 2 diabetes who did not
exercise were more likely to die during a
12-year period than their more active,
physically fit counterparts.4 Exercise is
associated with improved control of
blood pressure and of glycosylated hemoglobin (HbA1c) and cholesterol levels.
Clearly, people with diabetes can benefit
from exercise.
GUIDELINES FOR EXERCISE
Most patients with diabetes can exercise safely. However, it is important for
patients to undergo detailed medical
screening before beginning any exercise
regimen. The American Diabetes Association along with the American College
of Sports Medicine recently published a
joint position statement on exercise and
diabetes, including guidelines about preexercise evaluation.5
For patients who wish to participate
in low-intensity physical activity, such as
walking, health care providers should use
clinical judgment in deciding whether to
recommend pre-exercise testing. For exercise more vigorous than brisk walking
www.Consultant360.com
Primary Care Update
Exercise Can Improve Glycemic Control
or exceeding the demands of everyday
living, sedentary and older patients with
diabetes will likely benefit from being assessed for conditions that might be associated with risk of cardiovascular disease
(CVD), contraindicate certain activities,
or predispose to injuries, including severe
peripheral neuropathy, severe autonomic
neuropathy, and preproliferative or proliferative retinopathy. Before undertaking
new higher-intensity physical activity,
they are advised to undergo a detailed
medical evaluation and screening for
blood glucose control, physical limitations, medications, and macrovascular
and microvascular complications.
In general, the American Diabetes
Association recognizes that most persons
with type 1 and type 2 diabetes can and
should participate in regular physical
activity.
It is important for patients to work
closely with their physicians when starting any exercise regimen; exercise may
necessitate a reduction in insulin requirements for those with type 1 diabetes, because exercise has an insulin-like effect.
Therefore, exercise-induced hypoglycemia can occur in patients with diabetes
who take exogenous insulin. Subsequently, patients should monitor their blood
glucose level more closely when initiating
an exercise program, as the level will be
affected by the duration and intensity of
activity.
Aerobic exercise. Although all
types of exercise should be discussed with
patients with diabetes, keep in mind that
most research has focused on aerobic exercise. Numerous studies have documented the benefit of such exercise for
this population. Gregg and colleagues6
demonstrated that patients with diabetes
who walked at least 2 h/wk, compared
with inactive individuals, had a 30%
lower all-cause mortality rate and a 34%
lower CVD mortality rate. The lowest
mortality rates were for persons who
walked 3 to 4 h/wk and for those whose
walking regimen involved moderate increases in their heart and breathing rates.
Therefore, at a minimum, physicians
should emphasize aerobic exercises, such
as walking, when counseling patients
with diabetes.
www.Consultant360.com One simple suggestion for patients
is that they should use a pedometer,
which is an inexpensive tool that has
been shown to be effective. Patients are
recommended to walk 10,000 steps daily,
which translates to approximately 5
miles. This number is based on studies
that show 10,000 steps daily improves
cardiovascular fitness. On average, most
people take less than 5000 steps daily;
therefore, 10,000 steps will represent a
significant increase in activity.
Recommending that patients walk
10,000 steps daily provides them with a
simple goal—if, near the end of the day,
they have not walked 10,000 steps, they
should walk, go up and down the stairs,
or march or jog in place until they reach
the goal. Pedometers are also beneficial
because they provide patients instant
feedback on a daily basis that allows
them to continually revise their program.
Researchers estimate that 1 death
per year may be preventable for every 61
people who could be persuaded to walk
at least 2 h/wk, which is around 25
min/d, 5 d/wk. Moreover, the Diabetes
Prevention Program has suggested that
overweight persons who exercise for 30
min/d, 5 d/wk and make moderate dietary changes cut their risk of diabetes to
half of that for overweight individuals
with high blood glucose.7 These findings
are on par with the current physical activity recommendations from the US
Surgeon General for general health.
Exercise counseling is best when it
is specific. A walking program can help
condition patients by gradually increasing the frequency, time, and the distance
they walk (Box).
In a meta-analysis of 12 aerobic
training studies and 2 resistance-training
studies, Boule and colleagues8 showed
that exercise training reduced glycosylated hemoglobin by an amount that
should decrease the risk of diabetic complications. Hu and colleagues9 examined
the relationship of total physical activity
and incidence of type 2 diabetes in
women as part of the Nurses’ Health
Study. The study subjects were surveyed
about their level of aerobic activity, and
data from women whose primary exercise was walking were compared with
data from those who engaged in more
vigorous activities such as jogging, bicycling, or swimming. At the end of the
study, aerobic exercise decreased the risk
of type 2 diabetes, and greater physical
activity was associated with a substantial
reduction in diabetes risk.
Strength training. Some data indicate that strength training may aid people with type 2 diabetes. Because some
patients who have poor endurance and
are overweight find it difficult to engage
in aerobic activity, strength training may
be helpful in improving their functional
capacity and their physical strength for
increasing aerobic activity. Holten and
colleagues10 studied 10 patients with type
2 diabetes and 7 healthy men to determine the effects of a 6-week strengthtraining program on diabetes. The researchers found that study participants
who performed strength training for 30
minutes three times per week demonstrated increased insulin action in skeletal
muscle.
Castaneda and colleagues11 studied
43 Hispanic patients with type 2 diabetes
during a 16-week resistance-training program. At the end of the study, patients
who completed the program, compared
with a nonexercising control group, demonstrated a significant reduction in
HbA1c as well as a decrease in fasting insulin levels and waist circumference.
The American College of Sports
Medicine recommends that persons with
type 2 diabetes should undergo resistance
training at least 2 d/wk as part of a wellrounded exercise program. A minimum
of 8 to 10 exercises involving the major
muscle groups should be performed,
with each exercise including a minimum
of one set of 10 to 15 repetitions maintained to near fatigue.12 The American
Diabetes Association recommends for
nearly all patients with diabetes a moderate weight training program that involves
light weights and many repetitions for
maintaining or enhancing upper-body
strength.13
Gestational diabetes. Exercise may
also be beneficial for patients with gestational diabetes. Aerobic exercise has been
shown to decrease the need for insulin in
patients with gestational diabetes. Some
January 2013 n consultant
47
Primary Care Update
Exercise Can Improve Glycemic Control
data suggest that resistance exercise can
improve insulin sensitivity, glucose disposal rate, and glycemic control.
Brankston and colleagues14 evaluated the
effects of circuit-type resistance training
on the need for insulin in 32 women
with gestational diabetes who were randomly assigned to either diet or diet plus
resistance exercise. The exercise program
consisted of 8 exercises performed in a
circuit, typically 2 to 3 sets of 15 repetitions performed 3 times per week. At the
end of the study, the amount of insulin
prescribed was significantly lower in the
diet-plus-exercise group, and their initiation of insulin therapy was longer.
CONCLUSION
In addition to a healthy diet, patients with diabetes need to adopt a
healthy exercise regimen. Walking is a
simple activity that does not require any
special equipment or training, and it has
been shown to reduce morbidity and
mortality. Strength training is also an important component of a well-rounded
exercise program and has independently
been shown to produce benefits in those
with diabetes, such as reduced HbA1c
levels, increased insulin sensitivity, and
improved fasting blood glucose levels.
Regular physical activity is crucial for
maintaining optimal health and vitality,
especially in patients with diabetes. It is
therefore imperative to discuss the benefits of exercise with patients who have
diabetes.
n
REFERENCES:
1. C
enters for Disease Control and Prevention. CDC
National Center for Chronic Disease Prevention
and Health Promotion. 2011 National Diabetes
Fact Sheet. September 21, 2012. http://www.cdc.
gov/diabetes/pubs/factsheet11.htm. Accessed
June 18, 2012.
2. C
ho E, Rimm EB, Stampfer MJ, Willett WC,
Hu FB. The impact of diabetes mellitus and prior
myocardial infarction on mortality from all causes
and from coronary heart disease in men.
J Am Coll Cardiol. 2002;40(5):954-960.
3. K
aufman FR. Diabesity: The Obesity-Diabetes
Epidemic That Threatens America—And What We
Must Do to Stop It. New York: Bantam Books;
2005.
4. W
ei M, Gibbons LW, Kampert JB, Nichaman MZ,
Blair SN. Low cardiorespiratory fitness and physical inactivity as predictors of mortality in men with
type 2 diabetes. Ann Intern Med. 2000;132(8):
605-611.
5. C
olberg SR, Sigal RJ, Fernhall B, Regensteiner JG,
Blissmer BJ, Rubin RR, Chasan-Taber L, Albright
AL, Braun B; American College of Sports Medicine;
American Diabetes Association. Exercise and type
2 diabetes: the American College of Sports Medicine
and the American Diabetes Association: joint
position statement. Diabetes Care. 2010;33(12):
e147-e167.
6. G
regg EW, Gerzoff RB, Caspersen CJ, Williamson
DF, Narayan KM. Relationship of walking to mortality among US adults with diabetes. Arch Intern
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7. H
affner S, Temprosa M, Crandall J, et al. Intensive
lifestyle intervention or metformin on inflammation
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glucose tolerance. Diabetes. 2005;54(5):
1566-1572.
8. B
oule NG, Haddad E, Kenny GP, Wells GA,
Sigal RJ. Effects of exercise on glycemic control
and body mass in type 2 diabetes mellitus:
a meta-analysis of controlled clinical trials. JAMA.
2001;286(10):1218-1227.
9. H
u FB, Sigal RJ, Rich-Edwards JW, et al. Walking
compared with vigorous physical activity and risk
of type 2 diabetes in women: a prospective study.
JAMA. 1999;282(15):1433-1439.
10. H
olten MK, Zacho M, Gaster M, Juel C,
Wojtaszewski JF, Dela F. Strength training increases
insulin-mediated glucose uptake, GLUT4 content,
and insulin signaling in skeletal muscle in patients
with type 2 diabetes. Diabetes. 2004;53(2):
294-305.
11. Castaneda C, Layne JE, Munoz-Orians L, et al.
A randomized controlled trial of resistance exercise training to improve glycemic control in older
adults with type 2 diabetes. Diabetes Care.
2002;25(12):2335-2341.
12. Albright A, Franz M, Hornsby G, et al. American
College of Sports Medicine position stand. Exercise and type 2 diabetes. Med Sci Sports Exerc.
2000;32(7):1345-1360.
13. A
merican Diabetes Association. Standards of
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2012;35(Suppl 1):S11-S63.
14. Brankston GN, Mitchell BF, Ryan EA, Okun NB.
Resistance exercise decreases the need for insulin in overweight women with gestational diabetes
mellitus. Am J Obstet Gynecol. 2004;190(1):
188-193.
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