Effect of Lifestyle Interventions on Coronary Heart Disease Risk in Patients with Diabetes

Weight Management and Energy Balance

Obesity is an independent risk factor for hypertension, dyslipidemia, and CVD, increasing the risk of cardiovascular events and mortality in patients with type 2 diabetes. Distribution of body fat also plays a role in cardiometabolic risk; individuals with central adiposity, as evidenced by increased waist measurement or “apple” body shape, have higher risk. Elevated waist circumference is defined as greater than 100 cm (40 inches) for North American men and greater than 88 cm (35 inches) for North American women. The proposed Diabetes Federation cut points for other geographical areas and countries are somewhat lower. Most individuals with type 2 diabetes are overweight or obese and/or have an elevated waist circumference. Therefore weight reduction is commonly indicated for patients with type 2 diabetes.

Increased waist measurement is a surrogate marker for visceral adiposity, which is fat tissue within the peritoneal cavity surrounding the intra-abdominal organs. Visceral adiposity is metabolically active, secreting a number of cytokine-like factors, referred to as adipokines. Adipokines promote inflammation and a prothrombotic state and are associated with development of atherogenic dyslipidemia (hypertriglyceridemia, low high-density lipoprotein [HDL] cholesterol [HDL-C] level, and an elevated subfraction of small, dense low-density lipoprotein [LDL] cholesterol [LDL-C] level), insulin resistance, dysglycemia and elevated blood pressure. Inflammation, as measured by serum level of high-sensitivity C-reactive protein, is also associated with type 2 diabetes and CVD. Modest weight reduction of 5% total body weight in individuals with type 2 diabetes is associated with decreased visceral adiposity and improvement in serum lipid concentrations, insulin action, and fasting blood glucose, as well as reductions in blood pressure, serum markers of inflammation, and the need for diabetes medication(s). In some patients, substantial weight loss can lead to clinical resolution of type 2 diabetes (see also Chapters 2 , 9 , and 10 ).

Weight loss occurs when energy intake is lower than energy expenditure. An energy deficit of 500 to 1000 kcal/day (3500 to 7000 kcal/wk) usually results in a weight loss of 1 to 2 lb/wk. Rate of weight loss can vary, however, depending on genetic factors, age, fidgeting, amount of lean body mass, and habitual physical activity. Older individuals tend to lose weight more slowly than younger persons because metabolic rate declines by approximately 2% each decade. A higher lean body mass is associated with greater energy expenditure and therefore a higher rate of weight loss. Most overweight or obese adults will lose weight if they comply with a diet of 1000 to 1200 kcal/day for women or 1200 to 1600 kcal/day for men. An alternative approach to determining prescribed calorie content is based on current total body weight and is divided into five weight categories ( Table 12-1 ).

Investigators have attempted to define the dietary macronutrient composition that is optimal for weight reduction, improvement in cardiometabolic risk factors, and long-term weight maintenance in overweight and obese individuals, as well as patients with type 2 diabetes (see also Chapter 5 ). Overall, it appears that lower-carbohydrate diets (< 40% of total calories) may result in greater short-term weight loss, improvement in hypertriglyceridemia, and possibly improvement in insulin resistance and glycosylated hemoglobin, but degree of weight loss and improvement in cardiometabolic risk factors is similar to that seen with low-fat or high-protein diets at 1 to 2 years. Of note, however, is that many participants have difficulty maintaining the macronutrient composition of their assigned diet after 6 to 12 months, so the true impact of differing macronutrient composition dietary intake in the long term is not known. It is likely that the optimal macronutrient composition varies for different individuals with regard to long-term compliance. Therefore, dietary guidance should be individualized to the patient’s lifestyle, preferences, and culture. According to the American Diabetes Association (ADA) 2013 Position Statement, the mix of carbohydrate, protein, and fat may be adjusted to meet the metabolic goals and individual preferences of the person with diabetes.

The ADA, the Obesity Society, and the American Society for Nutrition recommend a 500- to 1000-kcal/day deficit through a diet that meets guidelines for reducing risk of comorbidities with obesity. Specifically, these organizations recommend that the dietary macronutrient content and nutritional quality be based on guidelines from the ADA, the American Heart Association (AHA), and the National Cholesterol Education Program—Adult Treatment Panel ( Box 12-1 ). These are evidence-based dietary interventions that have been shown to improve selected cardiovascular risk factors, including hypertension and LDL-cholesterol level, and therefore are appropriate for patients with type 2 diabetes. According to the 2013 ADA Position Statement, individuals who have prediabetes or diabetes should receive individualized medical nutritional therapy (MNT) as needed to achieve treatment goals, preferably provided by a registered dietitian familiar with the components of diabetes MNT. The ADA statement recognizes that for weight loss, low-carbohydrate, low-fat, calorie-restricted, or Mediterranean diets may be effective in the short term (up to 2 years). However, for patients on low-carbohydrate diets, it is recommended to monitor lipid profiles, renal function, and protein intake (for those with nephropathy) and adjust hypoglycemic pharmacotherapy as needed.

Box 12-1

Data from the ADA, the AHA, and the National Cholesterol Education Program Expert Panel.

Dietary Guidelines Associated with Cardiovascular Risk Reduction

Eat a variety of fruits, vegetables, whole grains, legumes, and low-fat or nonfat dairy products.

Choose lean meats and poultry without skin, and prepare them without added saturated and trans fat.

Consume two or more servings of fish per week (with the exception of commercially fried fish fillets).

Limit saturated fat to less than 7% of total calories.

Minimize intake of trans fat by greatly limiting foods containing partially hydrogenated vegetable oil.

Limit dietary cholesterol intake to less than 200 mg/day.

Consume 20 to 30 g of fiber daily.

Greatly limit foods and beverages with added sugars.

Choose and prepare foods with little or no salt. Limit sodium intake to 2300 mg/day or less, according to ADA guidelines (or less than 1500 mg/day per AHA guidelines).

Limit alcohol intake to ≤ two drinks per day for men and ≤ one drink per day for women.

Prepackaged meal replacements in the form of liquid shakes, bars, and entrees are a useful tool to simplify a prescribed diet and minimize errors with portion control and high-caloric-density food choices. Meal replacement diets can enhance weight loss, improve cardiovascular risk factors, and have shown durable weight loss for periods of 4 to 5 years. A meal replacement weight loss diet typically consists of replacing two food meals and two snacks with four approximately 110- to 200-kcal shakes or bars, plus one food meal consisting of lean protein, low-starch vegetables, a fruit serving, and a starch serving. Total daily caloric intake often ranges from 900 to 1300 kcal/day. For weight maintenance, individuals typically have two food meals and replace a third meal and one to two snacks per day with a shakes and/or bars. In a study of 119 patients with type 2 diabetes, use of prepackaged meal replacements, compared with calorie-equivalent usual-care diet, resulted in greater weight loss (− 3.0 ± 5.4 kg versus − 1.0 ± 3.8 kg), improved glycemic control with lower hemoglobin A1c (HbA1c) levels, improved quality of life, and better compliance with dietary recommendations after 1 year. Another study found that the use of liquid meal replacements for 12 weeks in patients with type 2 diabetes resulted in significantly greater weight losses and reductions in fasting blood sugar compared with a conventional diet with the same calorie goal.

With the prescription of a meal replacement diet, care must be taken to lower or discontinue medications that can lead to significant hypoglycemia, such as sulfonylureas, insulin secretagogues, and insulin. Required medication adjustments are based on the patient’s current glycemic control, the prescribed dietary carbohydrate content, and the anticipated rate of weight loss based on calorie deficit. Patients should monitor blood glucose on a scheduled basis, and assessment for further medication adjustments should be completed daily to weekly for the first 3 to 4 weeks on the diet and then at intervals of 2 to 4 weeks during weight loss.

Recently, the Look AHEAD (Action for Health in Diabetes) study examined whether cardiovascular morbidity and mortality in persons with type 2 diabetes were reduced through an intensive lifestyle intervention aimed at achieving and maintaining at least a 10% loss of body weight over 4 years. This large randomized controlled trial of 5145 participants included moderate-intensity exercise with a goal of 200 min/wk, a healthy diet that included portion-controlled foods, and behavior modification, versus a usual-care control group (diabetes support and education). The primary outcome was a composite of death from cardiovascular causes, or hospitalization for angina pectoris for up to 13.5 years. One-year results showed an average 8.6% weight loss, significant reduction of glycosylated hemoglobin, and reduction in several cardiovascular risk factors in the intervention group. Other important health benefits included improvement in obstructive sleep apnea, reduction in diabetes medications, maintenance of physical mobility, and improvement in quality of life. However, despite these numerous health improvements, the intensive lifestyle intervention did not reduce the rate of cardiovascular events and the trial was halted early.

Exercise and Physical Activity in the Prevention and Treatment of Type 2 Diabetes Mellitus

There is a pathophysiologic cascade by which physical inactivity predisposes to a cluster of cardiometabolic diseases, including type 2 diabetes mellitus. With an increasingly inactive lifestyle, skeletal muscle downregulates its capacity to convert nutritional substrates to adenosine triphosphate. Inactive skeletal muscle’s impaired ability to oxidize glucose and fatty acids is presumably mediated by several mechanisms, including decreased mitochondrial concentration and oxidative enzymes; a reduced ability to remove glucose from blood because of fewer capillaries and diminished glucose transporter; and an attenuated capacity to hydrolyze blood triglycerides to free fatty acids, secondary to decreased lipoprotein lipase activity. Collectively, these metabolic perturbations reduce the somatic capacity to burn fuel, resulting in hyperinsulinemia, insulin resistance, and hypertriglyceridemia, and ultimately increased cardiovascular risk. On the other hand, regular moderate-to-vigorous leisure-time physical activity, structured aerobic exercise, or both, can often reverse these adverse sequelae. A significant increase in physical activity and daily energy expenditure also improves insulin action in obesity, with or without a concomitant reduction in body weight and fat stores. This is an important (and often overlooked) salutary effect, suggesting that physical activity is as efficacious in preventing insulin resistance as losing body weight.

Several recent randomized controlled trials in patients with type 2 diabetes have investigated the effects of moderate-to-vigorous aerobic exercise and resistance training on cardiorespiratory fitness, modifiable cardiovascular risk factors, and arterial stiffness, with specific reference to changes in body weight and fat stores. Compared with the control group and/or counseling alone, supervised exercise produced significant improvements in cardiorespiratory fitness, upper and lower body strength, HbA1c, systolic and diastolic blood pressure, total serum cholesterol, HDL-C and LDL-C, body mass index (BMI), waist circumference, insulin resistance, inflammation (high-sensitivity C-reactive protein), leptin, and CHD risk scores, independent of body weight losses. Structured exercise durations exceeding 150 min/wk were associated with greater HbA1c declines than those of 150 min/wk or less (0.89% and 0.36% reductions, respectively). On the other hand, large-artery elasticity, assessed by measuring pulse wave velocity, did not improve. A systematic review and meta-analysis of the relevant literature from 1970 to 2009 revealed that combined aerobic exercise and resistance training, as well as aerobic exercise alone, were related to statistically significant declines in HbA1c, triglyceride levels, waist circumference, and systolic blood pressure among individuals with type 2 diabetes. In contrast, the meta-analysis found little support for the benefits of resistance training alone on cardiovascular risk factors, including changes in HbA1c or resting systolic blood pressure, in patients with diabetes. Others, however, have reported that resistance training alone is associated with reductions in HbA1c as compared with a control group of patients with type 2 diabetes.

Compared with overweight and obese individuals, those with a normal weight at the time of diabetes diagnosis have higher mortality rates, even after adjustment for potential confounding variables. Because these data extend the “obesity paradox” to patients with diabetes, other potential modulators of survival, including body composition, fat distribution, regular physical activity, and cardiorespiratory fitness, beyond the measurement of BMI, may help the medical community clarify the relationships among obesity, morbidity, and mortality in adults with diabetes.

Numerous investigations and systematic reviews have examined the relationships among habitual physical activity, cardiorespiratory fitness, diabetes, BMI, and mortality. The risk for all-cause and/or cardiovascular mortality is lower among overweight and obese individuals with good aerobic fitness than in individuals with normal BMI and low fitness. ^, This finding has also been reported in a study of African American and Caucasian veterans with diabetes, in whom the obesity paradox was observed along with an independent association between poor exercise capacity and mortality within BMI categories. Others have reported that higher levels of cardiorespiratory fitness are associated with a substantial reduction in health risk for a given level of visceral and subcutaneous fat, and that increased physical activity and/or cardiorespiratory fitness is inversely associated with all-cause and cardiovascular mortality in persons with diabetes. ^, Collectively, these data and other recent reports ^, strongly support the role of structured exercise, regular moderate-to-vigorous physical activity, or both, in interventions designed to prevent and treat type 2 diabetes, regardless of the patient’s BMI.

Cardioprotective Effects of Regular Exercise

Two meta-analyses ^, have now shown that regular exercise participation can decrease the overall risk of cardiovascular events by up to 50%, presumably from multiple mechanisms, including antiatherosclerotic, anti-ischemic, antiarrhythmic, antithrombotic, and psychological effects ( Fig. 12-2 ). As noted earlier, aerobic exercise, with and without resistance training, has favorable effects on the diabetic patient’s cardiovascular risk factor profile, as well as on coagulability, fibrinolysis, and coronary endothelial function. Because more than 40% of the risk reduction associated with exercise training cannot be explained by changes in conventional risk factors, a cardioprotective “vascular conditioning” effect, including enhanced nitric oxide vasodilator function, improved vascular reactivity, altered vascular structure, or combinations thereof, has been proposed. Decreased vulnerability to threatening arrhythmias and increased resistance to ventricular fibrillation have also been postulated to reflect exercise-related adaptations in autonomic control. As a result of endurance training, sympathetic drive at rest is reduced and vagal tone and heart rate variability are increased. Moreover, ischemic preconditioning before coronary occlusion, at least in animal models, can reduce subsequent infarct size and/or the potential for malignant ventricular arrhythmias. ^,

Physical Activity, Exercise Programming, and Prescription

In many patients with type 2 diabetes, adequate glycemic control can often be achieved by dietary changes, regular physical activity, structured exercise, and weight reduction. The exercise program should generally follow contemporary guidelines for the treatment of excessive body weight and fat stores, and other risk factors associated with this common metabolic condition (i.e., dyslipidemia, hypertension, inflammatory markers, fibrinolytic factors, waist circumference). Overall, individuals with type 2 diabetes have an increased risk of morbidity and mortality from CVD as compared with their age- and gender-matched counterparts without this comorbidity. Accordingly, a physical examination and a careful preliminary cardiovascular assessment, including peak or symptom-limited exercise testing, with estimated or directly measured peak oxygen consumption ( o ₂ peak), should be considered before beginning a vigorous (≥ 60% o ₂ reserve) exercise training program, where

With this formula,
o ₂ is generally expressed in mL O ₂ /kg/min or in metabolic equivalents (METs), where 1 MET = 3.5 mL O ₂ /kg/min. Both the AHA and the American College of Sports Medicine (ACSM) guidelines for exercise testing and prescription recommend that peak or symptom-limited exercise testing be considered before initiation of vigorous exercise training in individuals with known or suspected CVD, including patients with diabetes mellitus.

Type of Exercise

Aerobic (or endurance) exercise has been the most frequently studied mode of physical conditioning, and the resultant increases in cardiorespiratory fitness in patients with type 2 diabetes have been consistently associated with improvements in modifiable cardiovascular risk factors, independent of weight loss. The most effective exercises for the endurance phase use large muscle groups, are maintained continuously, and are rhythmic in nature, such as walking, jogging, elliptical training, stationary or outdoor cycling, swimming, rowing, stair climbing, and combined arm-leg ergometry. Other exercise modalities commonly used in structured exercise training programs for patients with type 2 diabetes include calisthenics, particularly those involving sustained total-body movement, recreational activities (e.g., golf, doubles tennis, pickleball), and resistance training. The last is a particularly important option, because traditional aerobic-conditioning regimens often fail to accommodate participants who require improved muscle strength or endurance to perform occupational or leisure-time activities. Moreover, studies have now shown that muscular strength is inversely associated with all-cause mortality, independent of cardiorespiratory fitness levels.

Because of the high prevalence of underlying ischemic heart disease, and the heightened risk for exertion-related cardiovascular events and orthopedic injuries, adoption of a moderate intensity (e.g., walking), rather than a vigorous physical activity program (e.g., jogging, running) may be more appropriate for diabetic patients, especially those who are middle-aged and older. Walking has several advantages over other forms of exercise during the initial phase of a physical conditioning program, including inherent neuromuscular limitations on the speed of walking (and therefore the rate of energy expenditure). Brisk walking programs can significantly increase aerobic capacity and reduce body weight and fat stores, particularly when the walking duration exceeds 30 minutes. Additional advantages of a walking program include accessibility, social companionship, lack of special equipment (other than a pair of well-fitted athletic shoes), an easily tolerable exercise intensity, and fewer musculoskeletal and orthopedic problems of the legs, knees, and feet than with jogging or running. Walking in water, with a backpack, or with a weighted vest are options for those who seek to progressively increase the exercise intensity and associated energy expenditure.

The Rule of 2 and 3 Miles per Hour (mph)

Because most diabetic patients, many of whom are overweight or obese, prefer to walk at moderate intensities, it is helpful to recognize that walking on level ground at 2 and 3 mph approximates 2 and 3 METs, respectively. For patients who prefer the slower walking pace (2 mph; 3.2 km/h), each 3.5% increase in treadmill grade adds approximately 1 MET to the gross energy cost. Therefore, patients who desire to walk at a 2-mph pace, but require a 4-MET workload for training, would be advised to add 7.0% grade to this speed. For patients who can negotiate the faster walking speed (3 mph; 4.8 km/h), each 2.5% increase in treadmill grade adds an additional 1 MET to the gross energy expenditure. Accordingly, a workload of 3 mph, 7.5% grade, would approximate an aerobic requirement of 6 METs. Use of this practical rule can be helpful to clinicians in prescribing treadmill exercise workloads for their diabetic patients, without the need for consulting tables, nomograms, or metabolic formulas or calculations.

Resistance Training

Although resistance exercise has generally been considered to be less effective in preventing and treating type 2 diabetes, some reviews suggest that it provides independent and additive benefits to an aerobic exercise program for virtually the entire cluster of associated cardiovascular risk factors. For example, numerous studies show that resistance training improves insulin sensitivity, significantly decreases HbA1c and blood pressure in diabetic and hypertensive adults, respectively, and reduces body fat stores and visceral adipose tissue in both men and women. In addition, the maintenance or enhancement of lean body mass from chronic resistance training is associated with a modest increase in basal metabolic rate, which over time may facilitate greater reductions in body weight than can be achieved with increased physical activity and/or structured exercise. Weight-training–induced attenuation of the hemodynamic response to lifting standardized loads has also been reported, which may decrease cardiac demands during daily activities such as carrying packages or lifting moderate to heavy objects. There are also intriguing data to suggest that strength training can increase endurance capacity without an accompanying increase in cardiorespiratory fitness.

Although the traditional weight-training prescription has involved performing each exercise three times (e.g., three sets of 10 to 15 repetitions per set), it appears that one set provides similar improvements in muscular strength and endurance, at least for the novice exerciser. Consequently, single-set programs performed at least two times a week are recommended rather than multiset programs, because they are highly effective, less time-consuming, and less likely to cause musculoskeletal injury or soreness. Such regimens should include 8 to 10 different exercises involving the trunk and upper and lower extremities at loads that permit 8 to 15 repetitions per set. At least 60 minutes of resistance training should be completed each week (e.g., two 30-minute sessions).

Lifestyle Physical Activity

Despite contemporary exercise guidelines and the much-heralded Surgeon General’s report, the traditional model for getting people to be more physically active (i.e., a regimented or structured exercise program) has been only marginally effective. Randomized clinical trials have now shown that a lifestyle approach to physical activity among previously sedentary adults has similar effects on cardiorespiratory fitness, body composition, and coronary risk factors as a structured exercise program. ^, These findings have important implications for public health, suggesting an alternative approach to sedentary people who, for one reason or another, are not ready to integrate a formal exercise commitment into their daily schedule. The skyrocketing prevalence of overweight and obesity and related sequelae (e.g., type 2 diabetes, metabolic syndrome) suggests the need for “real world” interventions designed to circumvent and attenuate barriers to achieving an adequate daily energy expenditure. Accordingly, physicians and allied health professionals should counsel patients to integrate multiple short bouts of physical activity into their lives. Nonexercise activity thermogenesis—the spontaneous physical activities of daily living (e.g., fidgeting while sitting, standing while reading, moving the lower extremities while working at the computer)—represents another source of energy expenditure for many people. Standing also elevates lipoprotein lipase, an enzyme that improves fat metabolism while reducing insulin resistance. ^, Thus, energy expenditure during nonexercise time may be as critical for preventative health as structured exercise time. Pedometers can be helpful in this regard, as can programs that use them (e.g., America on the Move) to enhance awareness of physical activity by progressively increasing daily step totals. According to one systematic review, pedometer users significantly increased their physical activity by an average of 2491 steps per day more than their control counterparts. The Activity Pyramid ( Fig. 12-3 ) has also been suggested as a model to combat America’s increasingly hypokinetic environment. This schematic presents a tiered set of weekly goals to promote improved cardiorespiratory fitness and health, building on a base that emphasizes the importance of accumulating at least 30 minutes of moderate-intensity activity on 5 or more days per week.

Intensity and Duration

There is some controversy regarding the most appropriate exercise intensity and duration that are needed to optimally physically condition patients with insulin resistance syndrome. Different risk factors associated with this condition may respond more favorably to different exercise dosages and intensities. For example, a randomized, controlled trial of previously inactive, overweight men and women with abnormal lipoprotein profiles compared the effectiveness of three different exercise regimens versus controls: high-amount, high-intensity exercise; low-amount, high-intensity exercise; and low-amount, moderate-intensity exercise. Although all exercise groups demonstrated improved responses on a variety of lipid and lipoprotein variables as compared with the control group, the most beneficial changes were noted in the high-amount, high-intensity exercise regimen. Because type 2 diabetes has been associated with increased body weight and fat stores, a sedentary lifestyle, and a low level of cardiorespiratory fitness, the initial exercise intensity should approximate at least 40% of the o ₂ or heart rate reserve or 55% of the maximal heart rate, at a rating of perceived exertion (6 to 20 category scale) of 11 (fairly light) or higher, for a minimum accumulated duration of 30 min/day. ^, Over time, in the absence of adverse signs and symptoms, the exercise intensity should be gradually increased, generally corresponding to a rating of perceived exertion up to 14 (somewhat hard to hard), to provide the stimulus to improve cardiorespiratory fitness and facilitate a progressive overload (i.e., attainment of goal energy expenditure).

The exercise intensity recommendation can be achieved with a combination of moderate and vigorous physical activity, which approximates 40% to 59% and 60% to 84% of o ₂ or heart rate reserve, respectively. The ACSM recommends that most adults engage in moderate-intensity exercise training for at least 30 min/day on at least 5 days of the week for a total of more than 150 min/wk, or vigorous exercise training for at least 20 min/day on at least 3 days of the week for a total of more than 75 min/wk, or a combination of moderate and vigorous-intensity exercise to achieve a total energy expenditure of more than 500 to 1000 MET/min/wk. When a combination is used, it has been suggested that the vigorous-intensity exercise time can be multiplied by 1.7 to allow this to be added to the moderate-intensity time. For example, in 1 week a diabetic patient could exercise on 3 days for 40 minutes at a moderate intensity and on another day for 20 minutes at a vigorous intensity, approximating 154 minutes of moderate-intensity activity (120 + [20 × 1.7]). Thus, this combination of moderate and vigorous exercise meets the minimum recommended weekly moderate-intensity exercise dosage (≥ 150 minutes). The 1.7 multiplication factor is derived from recommendations that 150 minutes of moderate-intensity exercise is equivalent to approximately 90 minutes of vigorous physical activity (a ratio of 1:1.7), and is compatible with a recent position statement from the ACSM and ADA.

Frequency

The frequency of exercise is an important consideration when structured exercise and/or increased lifestyle physical activity are used to treat the abnormalities associated with type 2 diabetes, especially insulin sensitivity and glucose use. Although even twice-weekly exercise sessions may favorably influence glycemic control, patients with type 2 diabetes should exercise at least 3 days each week with no more than 2 consecutive days without training, because increases in insulin sensitivity decline markedly by 48 hours after exercise. Nevertheless, more frequent exercise (i.e., at least 5 days/wk) may serve to maximize both the acute glucose-lowering effect and the effect on cardiovascular risk reduction.

A summary of exercise prescription and physical activity guidelines for patients with type 2 diabetes mellitus is shown in Table 12-2 , with specific reference to the type of exercise, major goals and objectives, and the recommended intensity, frequency, and duration. It should be emphasized, however, that if these recommended levels of exercise are deemed by the patient to be unrealistic or excessive, the patient should be encouraged to achieve more moderate exercise dosages or intensities, because the primary beneficiaries are individuals with and without CVD who are in the least fit, least active subgroup (bottom 20%). ^,

Table 12-2

Exercise Recommendations for Patients with Type 2 Diabetes Mellitus

Type of Exercise *	Major Goals and Objectives	Intensity, Frequency, Duration
Aerobic (large muscle activities)—for example, walking, jogging, stationary or outdoor cycling, swimming	Increase o 2 peak; ADLs	40%-84% o 2 R † or HRR; 55%-89% HR max; RPE 11-16 (6-20 scale)
	Improve glycemic control and coronary risk factors	No more than 2 consecutive days without exercising; four to five sessions per week (or more) may be needed to reduce body weight and fat stores
	Decrease rate-pressure product during submaximal exercise	≥ 150 min/wk or ≥ 90 min/wk for moderate-intensity or vigorous-intensity exercise, respectively; ≥ 20 min per session
	Induce other cardioprotective benefits (e.g., enhanced nitric oxide vasodilator function, improved vascular reactivity, altered vascular structure, increased resistance to ventricular tachycardia and fibrillation)	For moderate-intensity activity (≤ 59% o 2 R or HRR and/or ≤ 69% HR max and/or RPE ≤ 13), multiple shorter periods of exercise (10- to 15-min exercise bouts) accumulated throughout the day may elicit similar (or even greater) reductions in body weight and fat stores than a single bout of the same duration
		Complement structured exercise with an increase in daily lifestyle activities (walking breaks at work, gardening, household activities); move more, sit less
Resistance training (multijoint exercises, large muscle groups, progressive)	Increase muscle strength and endurance	8-10 different exercises that work major muscle groups; weight loads gradually increased over time
	Increase ability to perform leisure and occupational activities and ADLs	≥ 2 times/wk
	Decrease the rate-pressure product at any given resistance (e.g., during lifting or carrying objects)	Moderate to vigorous intensity; one to four sets of 8-10 reps at a weight that cannot be lifted more than 8-10 times, ‡ or 12-15 reps at a weight that cannot be lifted more than 12-15 times (for patients with known CHD), with 1- to 2-min rest periods between sets
	Assist in the maintenance of basal metabolic rate by maintaining or increasing lean body mass over time
Flexibility and stretching (upper and lower body ROM activities)	Improve balance and agility	Static stretches: hold for 10-30 sec
	Decrease risk of musculoskeletal and orthopedic injury	2-3 days/wk

ADLs = Activities of daily living; HR max = maximal heart rate; HRR = heart rate reserve; ROM = range of motion; RPE = rating of perceived exertion (6-20 scale);
o ₂ R =
o ₂ reserve.

* Aerobic exercise should be preceded by a warm-up (approximately 10 minutes) and followed by a cool-down (5-10 minutes) at a reduced exercise intensity (e.g., slow walking). Stretching (5-10 minutes) may be incorporated before or after the endurance exercise phase.

† o ₂ reserve formula = ( o ₂ peak − o ₂ rest) × 40%-84% intensity + o ₂ rest, where o ₂ values are expressed in METs.

‡ Approximates 70%-84% of one repetition maximum.