Exercise and Type 2 Diabetes Medicine & Science in Sports & Exercise Volume 32(7) July 2000 pp 1345-1360
Diabetes • Type 1 • Insulin dependent diabetes mellitus (IDDM) • Juvenile • Type 2 • Non- Insulin dependent diabetes mellitus (NIDDM • Adult onset (less so recently) • Gestational (temporary) • Secondary (pancreatitis, etc.)
Fasting plasma glucose greater than 126. Symptoms such as polyuria, polydipsia, and unexplained weight loss with plasma glucose over 200. 2-hour plasma glucose greater than 200 during an oral glucose tolerance test Criteria
What is HbA1C? • Glucose sticks to the hemoglobin to make a 'glycosylated hemoglobin', called hemoglobin A1C or HbA1C. The more glucose in the blood, the more hemoglobin A1C or HbA1C will be present in the blood. • Red cells live for 8 -12 weeks before they are replaced. By measuring the HbA1C it can tell you how high your blood glucose has been on average over the last 8-12 weeks. A normal non-diabetic HbA1C is 3.5-5.5% (this varies between hospitals). In diabetes 4-6% is acceptable. • The HbA1C test is currently one of the best ways to check diabetes is under control; it is the blood test that gets sent to the laboratory, and it is done on the spot in some hospital clinics. Remember, the HbA1C is not the same as the glucose level.
Glucose Uptake • Normal glucose uptake • Insulin • GLUT-1 and GLUT-4 • Effective transport • Glucose uptake in diabetes • Insulin (Type I) • GLUT-1 and GLUT-4 (Type II) • Defective transport
Factors • Genetic influence • not well understood • Environmental • age • obesity • fat distribution • ethnicity • family history • low socioeconomic status • physical inactivity • diet • number of children born
Pathophysiology • Insulin resistance (or action) • GLUT-4 proteins • Insulin receptor substrate • Insulin secretion (or deficiency) • Causes: • genetics • chronic hyperglycemia • high fatty acid levels
Pathophysiology • Insulin resistance • Defective insulin receptors • Defective GLUT-4 • Insulin deficiency
Hyperglycemia • Damage to capillaries • Increase clot formation • Nerve damage • Associated with other diseases
Treatment • Goal: achieve optimal glucose and fatty-acid levels • Exercise • improves insulin sensitivity • improves lipid levels and hypertension • Medication
Acute Effects of Exercise • Blood glucose levels? • Decrease • Increase if the exercise is at a high intensity level • Causes? • Increase in muscle glucose uptake • Decrease in hepatic glucose production
Acute Effects of Exercise • Insulin resistance • Some, but not all studies, show an increase in insulin sensitivity. • How long? • 12-24 hours • Recommendations • Regular activity performed at low-to-moderate intensity is recommended
Chronic Effects • Type 2 diabetics: low functional capacity • Regular exercise causes typical physiological changes including those that help prevent CVD
Hypertension • 60% of people with type 2 diabetes
Metabolic Control • Aerobic exercise improves glucose tolerance and HBAC1 levels • Less effects in older patients • Effects show in as little as 7 days • Frequency of exercise is key • Inverse relationship between physical activity and mortality from type 2 diabetes • Exercise may help improve glucose disposal
Lipids and Lipoproteins • Exercise may improves lipid profile of type 2 diabetics, slow down atherosclerosis, and related mortality • Triglycerides • Total cholesterol • HDL:TC ratio • Some studies show no effect • Weight loss may be more important than exercise for improving lipid levels.
Weight Loss • Moderate weight loss (10-15% of 4.5-9.1 kg) has positive effect • Nutrition and exercise are most effective • Exercise mobilizes upper body fat • Loss of visceral fat may improve metabolic control • Exercise levels needed for weight loss are difficult in type 2 diabetics
Physical Activity • As physical activity decreases in societies, type 2 diabetes increases • Groups of people with type 2 diabetes are typically less active and/or have higher glucose and insulin levels • Physical fitness may provided some protection against type 2 diabetes • Physical activity plays a major role in treating type 2 diabetes
Physical Activity • Frequency: • 3 non-consecutive days up to 5 days a week • Acute effects of exercise on glucose levels last up t 72 hours • Daily exercise will maximize weight loss • Intensity: • Low to moderate (40-70% VO2max) • Enhance adherence, injury, and foot trauma • Autonomic neuropathy affects HR response during exercise • RPE
Physical Activity • Duration • Initially 10-15 minutes per session • Minimum of 30 minutes per session • Three 10 minutes sessions per day • Optimal would be 60 minutes • Mode • Control of intensity, easily maintained, low skill, personal interests, safe, and maximize caloric expenditure • May need to be non-weight baring • Resistance training?
Physical Activity • Progression • Age, functional capacity, medical status, personal preferences, goals, etc. • Frequency and duration before intensity • Limitations • Drop out rate is high with type 2 diabetics • Low number of type I muscle fibers and low capillary density • Lower anaerobic threshold
Complications • Glucose uptake increases during exercise from 2-3 mg/kg/min with moderate exercise to 5-6 mg/kg/min with high intensity exercise. • Hypoglycemia is less likely with Type 2 patients. • Insulin injections • 1 hour before exercise in non-exercising muscle • Self blood glucose monitoring is recommended
Long-term Complications • Macro- and microvascular complications can be made worse through exercise. • Physical exam before starting an exercise program
Complications • The risk of cardiovascular disease is 50% and 150% greater in men and women, respectively, with type 2. • If autonomic neuropathy is present…? • Low-level daily activities and perhaps non-weight bearing. • If peripheral neuropathy? • Non-weight baring • If nephrophathy… • Avoid blood pressure > 180 mm Hg • If retinopathy… • Limit BP increases to 20-30 mm Hg and avoid head down activities, jarring activities and activities where the arms are over the head.
Maintenance of Exercise • Transtheoretical model • Contemplation stage: deals with benefits of exercise • Action stage: deals with exercise options • Ease of Access • Ease of Performance • Maintenance stage: deals with a proper exercise program • Self-efficacy theory
Conclusions • Physical activity affords significant acute and chronic benefits for those with type 2 diabetes. • The benefits of chronic physical activity are more numerous than those of acute physical activity, emphasizing the need for regular participation by those with type 2 diabetes and those at risk for this form of diabetes. • Unfortunately, physical activity is underutilized in the management of type 2 diabetes. • This may be due to lack of understanding and/or motivation on the part of the person with diabetes and lack of clear recommendations, encouragement, and follow-up by health care professionals.
Conclusions • Several factors including muscle fiber composition, low capillary density, obesity, and older age require that physical activity be initiated at lower intensity/duration and be increased gradually to reduce risks and contribute to maintenance of physical activity by those with type 2 diabetes. • Attention to the patient's stage of readiness and factors that will encourage adoption and maintenance of regular physical activity are extremely important for successful use of physical activity as a therapeutic intervention. • Health care professionals must address physical activity more seriously in this patient population because most people with type 2 diabetes have the potential to derive benefits from regular, moderate levels of physical activity.
Exercise and Prevention of Type 2 Diabetes • 6% decrease for every 500 kcals/week • Other evidence • Inactivity and sedentary lifestyle • Da Qing study (Pan, et al. 1997) • Controls 68% increase in Type 2 • Diet 44% • Diet plus exercise 46% • Exercise 41%
Kohl HW ; Gordon NF ; Villegas JA ; Blair SN Cardiorespiratory fitness, glycemic status, and mortality risk in men Diabetes Care 1992 Feb; 15(2): 184-92 • OBJECTIVE--To determine the association of baseline cardiorespiratory fitness to all-cause mortality across the range of blood glucose levels. • RESEARCH DESIGN AND METHODS--Data from a prospective study of 8715 men (average age 42 yr), followed for an average of 8.2 yr (range 1-15 yr), were analyzed. Cardiorespiratory fitness was assessed by maximal-exercise treadmill testing. Men with evidence of clinical vascular disease or who did not achieve 85% of their age-predicted maximum heart rate during exercise testing were excluded from analyses. • RESULTS--Age-adjusted death rates increased with higher levels, of fasting blood glucose. Regardless of glycemic status, fit men had lower age-adjusted all-cause death rates than their less fit counterparts. For men with fasting blood glucose greater than or equal to 7.8 mM or physician-diagnosed non-insulin-dependent diabetes mellitus (NIDDM), the age-adjusted death rates per 10,000 person-yr of follow-up in unfit and fit subjects were 82.5 and 45.9, respectively. The age-adjusted relative risk of death due to all causes was significantly elevated in the lower-fitness group within each of three glycemic status levels: fasting blood glucose less than 6.4 mM; relative risk (RR) = 1.93 (95% confidence interval [95% CI] 1.15-3.26); fasting blood glucose 6.4-7.8 mM; RR = 3.42 (95% CI 2.27-5.15); and fasting blood glucose greater than or equal to 7.8 mM or with NIDDM, RR = 1.80 (95% CI = 1.25-2.58). Multivariate analyses, controlling for risk factors of mortality (age, resting systolic blood pressure, serum cholesterol, body mass index, family history of heart disease, follow-up interval, and smoking habit) showed a higher risk of death due to all causes for unfit compared with fit men. Multivariate risks of death associated with low fitness, compared with higher fitness (RR), in the three glycemic status groups were: fasting blood glucose less than 6.4 mM, RR = 1.38 (95% CI 1.09-1.74); fasting blood glucose 6.4-7.8 mM, RR = 1.61 (95% CI 0.91-2.86); and fasting blood glucose greater than or equal to 7.8 mM or with NIDDM, RR = 1.92 (95% CI 0.75-4.90).
Pan, X.R. et al. Effects of diet and exercise in preventing NIDDM in people with impaired glucose tolerance. The Da Qing IGT and Diabetes Study. Diabetes Care 1997 Apr; 20(4): 537-44 • OBJECTIVE: Individuals with impaired glucose tolerance (IGT) have a high risk of developing NIDDM. The purpose of this study was to determine whether diet and exercise interventions in those with IGT may delay the development of NIDDM, i.e., reduce the incidence of NIDDM, and thereby reduce the overall incidence of diabetic complications, such as cardiovascular, renal, and retinal disease, and the excess mortality attributable to these complications. • RESEARCH DESIGN AND METHODS: In 1986, 110,660 men and women from 33 health care clinics in the city of Da Qing, China, were screened for IGT and NIDDM. Of these individuals, 577 were classified (using World Health Organization criteria) as having IGT. Subjects were randomized by clinic into a clinical trial, either to a control group or to one of three active treatment groups: diet only, exercise only, or diet plus exercise. Follow-up evaluation examinations were conducted at 2-year intervals over a 6-year period to identify subjects who developed NIDDM. Cox's proportional hazard analysis was used to determine if the incidence of NIDDM varied by treatment assignment. • RESULTS: The cumulative incidence of diabetes at 6 years was 67.7% (95% CI, 59.8-75.2) in the control group compared with 43.8% (95% CI, 35.5-52.3) in the diet group, 41.1% (95% CI, 33.4-49.4) in the exercise group, and 46.0% (95% CI, 37.3-54.7) in the diet-plus-exercise group (P < 0.05). When analyzed by clinic, each of the active intervention groups differed significantly from the control clinics (P < 0.05). The relative decrease in rate of development of diabetes in the active treatment groups was similar when subjects were stratified as lean or overweight (BMI < or > or = 25 kg/m2). In a proportional hazards analysis adjusted for differences in baseline BMI and fasting glucose, the diet, exercise, and diet-plus-exercise interventions were associated with 31% (P < 0.03), 46% (P < 0.0005), and 42% (P < 0.005) reductions in risk of developing diabetes, respectively. • CONCLUSIONS: Diet and/or exercise interventions led to a significant decrease in the incidence of diabetes over a 6-year period among those with IGT.