Exercise is a cost-effective, nonpharmacologic way to improve glucose control, reduce weight and cardiovascular risk, and prevent diabetes complications
Exercise is a cost-effective, nonpharmacologic way to improve glucose control, reduce weight and cardiovascular risk, and prevent diabetes complications.1,2 Yet many patients with diabetes do not exercise on a regular basis.1,2
Patients may not know how to best implement exercise as a lifestyle change. Often, physical activity advice alone is viewed as a physical activity intervention.3 But advice is not an intervention. This review of the literature examined the HbA1C-lowering capacity of various forms of exercise and exercise programs.
Review of the Literature
This search for evidence used the Cumulative Index to Nursing and Allied Health Literature, PubMed and ancestry searches. It yielded several meta-analyses about the effects of exercise on diabetes.
In a meta-analysis of controlled clinical trials, Boulé et al4 found 14 studies to evaluate the effects of exercise interventions in adult patients with type 2 diabetes (T2DM). Using 12 aerobic training studies and two resistance training studies lasting more than 8 weeks, the weighted mean of HbA1C was 7.65% in exercise groups versus 8.31% in the control groups. The aerobic training studies included exercises such as cycling, jogging, walking, rowing, swimming and skiing. The resistance training studies used weight training of two to three sets with 10 to 20 repetitions. The researchers found no statistically significant difference in post-intervention body mass between exercise and control groups (83.02 kg vs. 82.48 kg).4
In another systematic review, Thomas et al5 analyzed the independent effect of exercise on patients with T2DM. In 14 randomized controlled trials with 377 participants, researchers compared exercise against no exercise in patients with T2DM. The exercise intervention showed statistically and clinically significant improvement in glycemic control (0.6% decrease in HbA1C); no significant difference in BMI between groups; reduced visceral adipose tissue with exercise at -45.5 cm2; no reported adverse effects or diabetes complications in the exercise group; increased insulin response at 131 AUC; decreased plasma triglycerides at -0.25 mmol/L; and no significant difference in quality of life, plasma cholesterol or blood pressure between groups.5
Orrow and colleagues6 performed a systematic review and meta-analysis of 16 trials to determine whether primary care-based trials of physical activity promotion showed effects in sedentary adults or if exercise referral interventions are more effective. In 13 primary care-based trials, researchers found small to medium positive effects of physical activity promotion at 12 months. Three trials of exercise referral showed small, nonsignificant effects on self-reported physical activity at 12 months.6
In a meta-analysis and systematic review of 47 randomized controlled trials of structured exercise regimens versus physical activity advice alone, Umpierre et al3 found that HbA1c decreased by 0.67% with structured exercise, by 0.89% with more than 150 minutes per week of structured exercise, and by 0.58% with advice about physical activity and diet only.
In a systematic review and meta-analysis of 12 randomized controlled trials, Yang and associates7 investigated the efficacy and safety of resistance training versus aerobic exercise and found a greater reduction of glycosylated hemoglobin with aerobic exercise than with resistance training at a difference of 0.18%. With sensitivity analysis, the difference was not statistically significant. Yang et al7 also showed a statistically significant difference in aerobic training versus resistance training in body mass index at 0.22 peak oxygen consumption at -1.84 mL/kg/min and maximum heart rate at 3.44 beats per minute. Relative risk for adverse events of exercise in resistance versus aerobic groups was 1.17, and relative risk for serious adverse events was 0.89.
Casey et al8 conducted a qualitative study about physical activity facilitators and barriers after the completion of a supervised exercise program. Three focus groups with a total of 16 participants led by a moderator discussed current exercise engagement, reasons for continuing or discontinuing regular exercise, and ways to incorporate exercise on a daily basis. Casey et al8 reported that motivation was the most important factor during and after an exercise program. Participants appreciated monitoring, encouragement and accountability. The researchers found that patients needed better transition post-program. They described the most optimal exercise program as flexible and close geographically, and they found walking to be their most frequent form of exercise.
Synthesis of Results
Results from these studies show beneficial effects of exercise on type 2 diabetes but not a significant reduction in BMI.4,5 The most important factor is adherence to at least one type of exercise routine.7
Referrals to exercise programs produce beneficial results, but results may not be long-standing. In primary care settings, physical activity advice is commonly used as a means for physical activity intervention. Although structured exercise training produces greater reduction in HbA1C, physical activity advice could be used if given with dietary advice as well. Physical activity and dietary advice may produce reduced HbA1C, but patients prefer structure and ongoing monitoring and support. Together these increase motivation to provide a lasting lifestyle change.
Implications for Practice
Exercise is beneficial to patients with diabetes even without obvious outward physical changes. This is a noteworthy fact to discuss when counseling patients with T2DM.4,5 Patients may give up on an exercise routine if the number on the scale does not budge or the pant size does not change. They should not.
To achieve A1C reduction, consider all factors, including barriers to exercise,8 along with ways to ensure long-term adherence. The best exercise intervention is aerobic activity.4 It can be performed with or without resistance.
The key is for the patient to consistently perform the exercise for at least 150 minutes per week.3 Exercise should be recorded and reviewed at each visit, just as blood sugar logs are reviewed to provide ongoing monitoring.8
Working with your patient to build an exercise program that incorporates knowledge gained from the review of evidence can set a foundation for improved long-term outcomes in diabetes.
1. American Diabetes Association. Standards of medical care in diabetes. Diabetes Care. 2014;37(1):S14-S80.
2. Colberg SR, et al. 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.
3. Umpierre D, et al. Physical activity advice only or structured exercise training and association with HbA1c levels in type 2 diabetes: a systematic review and meta-analysis. JAMA. 2011;305(17):1790-1799.
4. Boulé NG, et al. Effects of exercise on glycemic control and body mass in Type 2 Diabetes Mellitus. JAMA. 2001;286(10):1218-1227.
5. Thomas D, et al. Exercise for type 2 diabetes mellitus. Cochrane Datab System Rev. 1996;CD002968.
6. Orrow G, et al. Effectiveness of physical activity promotion based in primary care: systematic review and meta-analysis of randomised controlled trials. BMJ. 2012;344(e1389). http://dx.doi.org/10.1136/bmj.e1389.
7. Yang Z, et al. Resistance exercise versus aerobic exercise for type 2 diabetes: a systematic review and meta-analysis. Sports Med. 2013;44(4):487-499.
8. Casey D, et al. Understanding physical activity facilitators and barriers during and following a supervised exercise programme in Type 2 diabetes: a qualitative study. Diabetic Medicine. 2009; 27(1).79-84.