Behavior and biology: the prevention of type 2 diabetes

Type 2 diabetes mellitus (DM), characterized by insulin resistance and a beta-cell secretory defect, appears to result from a number of gene and environmental interactions. There are marked differences in the phenotypic expression of type 2 DM with individuals exhibiting varying levels of insulin resistance and impairments in insulin secretion. Study results indicate that a number of healthy lifestyle behaviors, such as increased physical activity and reduced intake of dietary fat, are associated with decreased development of type 2 DM. This article explores the genetic and environmental factors associated with the development of type 2 DM along with the role of lifestyle modifications in the prevention of this disease.     

Physical activity and diabetes mellitus

Diabetes mellitus (DM), a metabolic syndrome consisting of two main groups, type 1 and 2, is characterized by aboslute or relative insulin deficiency or insulin resistance. Individuals with DM take part in physical activity for health promotion, disease management, and or recreational or competitive sports. Several studies confirm the beneficial role of physical activity in favorably altering the prognosis of DM. Exercise as a therapeutic strategy has potential risks, too. Hence, sports medicine physicians caring for athletes with diabetes have several important responsibilities. Diabetic education; pre-participatory evaluation for vascular, neurological, retinal or joint disease; diabetic status and control; promotion of blood glucose self-monitoring; and individualized dietary, medication, and physical activity plans are essential to achieve safe and enjoyable outcomes in individuals with diabetes who are embarking on physical activity. The authors have stated that they do have a significant financial interest or other relationship with a product manufacturer or provider of services discussed in this article. The authors do not discuss the use of off-label products, which includes unlabeled, unapproved, or investigative products or devices.     

Diet and exercise among adults with type 2 diabetes: findings from the third national health and nutrition examination survey (NHANES III)

OBJECTIVE: To describe diet and exercise practices from a nationally representative sample of U.S. adults with type 2 diabetes. METHODS: We analyzed data from 1,480 adults older than 17 years with a self-reported diagnosis of type 2 diabetes in the Third National Health and Nutrition Examination Survey (NHANES III). Fruit and vegetable consumption was obtained from a food frequency questionnaire; the percentages of total calories from fat and saturated fat were obtained from a 24-h food recall. Physical activity was based on self report during the month before the survey. RESULTS: Of individuals with type 2 diabetes, 31% reported no regular physical activity and another 38% reported less than recommended levels of physical activity. Sixty-two percent of respondents ate fewer than five servings of fruits and vegetables per day. Almost two thirds of the respondents consumed >30% of their daily calories from fat and >10% of total calories from saturated fat. Mexican Americans and individuals over the age of 65 years ate a higher number of fruits and vegetables and a lower percentage of total calories from fat. Lower income and increasing age were associated with physical inactivity. Thirty-six percent of the sample were overweight and another 46% were obese. CONCLUSIONS: The majority of individuals with type 2 diabetes were overweight, did not engage in recommended levels of physical activity, and did not follow dietary guidelines for fat and fruit and vegetable consumption. Additional measures are needed to encourage regular physical activity and improve dietary habits in this population.     

Lifestyle modifications and surgical options in the treatment of patients with obesity and type 2 diabetes mellitus

This article reviews recent developments in the behavioral and surgical treatment of obesity and type 2 diabetes mellitus (T2DM). Randomized controlled trials of comprehensive lifestyle-modification programs, which include dietary interventions, physical activity, and behavioral therapy, have shown weight losses of 7% to 10% of initial body weight within 4 to 6 months after treatment. These programs also reduce the likelihood of developing T2DM by 58% for individuals with impaired glucose tolerance. Long-term maintenance of these improvements requires continued implementation of the program diet, physical activity, and self-regulatory behaviors. This can be successfully facilitated by continued patient-provider contact, which is frequently delivered by phone, mail, email, or online. However, these benefits may have less impact on those with extreme obesity or more significant health problems. For these individuals, bariatric surgery may be a more appropriate treatment. Bariatric surgical procedures induce mean weight losses of 15% to 30% of initial body weight (depending on the procedure) within 2 years after surgery, as well as a 45% to 95% rate of diabetes remission. Familiarity with these developments can help physicians and patients to determine which combinations of behavioral, medical, and surgical interventions are appropriate for the treatment of obesity and T2DM.     

Pediatric obesity & type 2 diabetes

This article focuses on (a) identifying obesity and other risk factors for developing type 2 diabetes, (b) differentiating between pediatric type 1 diabetes and type 2 diabetes, and (c) treating pediatric type 2 diabetes. Obesity has significant implications on a child's health, including an increased risk for insulin resistance and progression to type 2 diabetes. Type 2 diabetes in children, characterized by insulin resistance and relative pancreatic b-cell failure due to the increased demand for insulin production, has now reached epidemic proportions. Longitudinal research on pediatric type 2 diabetes, however, is lacking because this epidemic is relatively new. Treatment of type 2 diabetes in children is focused on lifestyle modification with weight management/increased physical activity, and pharmacological management through oral medication or insulin therapy. Because children with type 2 diabetes are at risk for developing diabetes-related complications earlier in life, they need to be closely monitored for comorbidities.     

Look AHEAD (Action for Health in Diabetes): design and methods for a clinical trial of weight loss for the prevention of cardiovascular disease in type 2 diabetes

Overweight and obesity are major contributors to both type 2 diabetes and cardiovascular disease (CVD). Moreover, individuals with type 2 diabetes who are overweight or obese are at particularly high risk for CVD morbidity and mortality. Although short-term weight loss has been shown to ameliorate obesity-related metabolic abnormalities and CVD risk factors, the long-term consequences of intentional weight loss in overweight or obese individuals with type 2 diabetes have not been adequately examined. The primary objective of the Look AHEAD clinical trial is to assess the long-term effects (up to 11.5 years) of an intensive weight loss program delivered over 4 years in overweight and obese individuals with type 2 diabetes. Approximately 5000 male and female participants who have type 2 diabetes, are 45-74 years of age, and have a body mass index >or=25 kg/m(2) will be randomized to one of the two groups. The intensive lifestyle intervention is designed to achieve and maintain weight loss through decreased caloric intake and increased physical activity. This program is compared to a control condition given diabetes support and education. The primary study outcome is time to incidence of a major CVD event. The study is designed to provide a 0.90 probability of detecting an 18% difference in major CVD event rates between the two groups. Other outcomes include components of CVD risk, cost and cost-effectiveness, diabetes control and complications, hospitalizations, intervention processes, and quality of life.     

Physical activity and diabetes: opportunities for prevention through policy

Over the past decade, the prevalence of type 2 diabetes mellitus has reached epidemic levels in the United States and other developed countries. With a concomitant rise in obesity levels in the United States and advances in the treatment of diabetes and its complications, the prevalence of diabetes is expected to continue to rise through the year 2050. Despite strong evidence that regular physical activity can prevent or delay the onset of diabetes, too many Americans are not meeting the recommended levels of regular physical activity. Although most physical activity interventions to date have been focused on characteristics of the individual, more-recent studies have considered how changing characteristics of the social and physical environment in which people live may ultimately have a greater impact on increasing population levels of physical activity. Policy interventions are a way to make sustainable changes in the physical environment of a community and thus provide support for other intrapersonal and interpersonal behavioral change interventions. Policy changes also can affect the social norms that shape behavior. The purposes of this perspective article are: (1) to describe the rationale for population approaches to primary prevention of type 2 diabetes, (2) to discuss how policy interventions can increase physical activity levels within populations, and (3) to provide recommendations for the role of physical therapists in interventions that can increase the level of physical activity in communities. Public health approaches to curb the diabetes epidemic are urgently needed. Policy interventions to increase population levels of physical activity show promise for diabetes prevention. Physical therapists are uniquely suited to influence primary prevention efforts for diabetes.     

An obligation for primary care physicians to prescribe physical activity to sedentary patients to reduce the risk of chronic health conditions

Physical inactivity increases the risk of many chronic disorders. Numerous studies have convincingly demonstrated that undertaking and maintaining moderate levels of physical activity (eg, brisk walking 3 hours a week) greatly reduces the incidence of developing many chronic health conditions, most notably type 2 diabetes mellitus, obesity, cardiovascular disease, and many types of cancers. However, the underlying mechanistic details of how physical activity confers such protective effects are not well understood and consequently constitute an active area of research. Although changing an individual's ingrained behavior is commonly perceived to be difficult, encouraging evidence suggests that intensive and repeated counseling by health care professionals can cause patients to become more physically active. Therefore, counseling patients to undertake physical activity to prevent chronic health conditions becomes a primary prevention modality. This article summarizes the vast epidemiologic and biochemical evidence supporting the many beneficial health implications of undertaking moderate physical activity and provides a rationale for incorporating physical activity counseling as part of routine practice in the primary care setting.     

Clinical implications of the insulin resistance syndrome

Insulin resistance syndrome (IRS), also termed syndrome X, is a distinctive constellation of risk factors for the development of type 2 diabetes mellitus and cardiovascular disease. The syndrome's hallmarks are glucose intolerance, hyperinsulinemia, a characteristic dyslipidemia (high triglycerides; low high-density lipoprotein cholesterol, and small, dense low-density lipoprotein cholesterol), obesity, upper-body fat distribution, hypertension, and increased prothrombotic and antifibrinolytic factors. Insulin resistance, caused by a complex of genetic and environmental influences, is now recognized not just as a mechanism contributing to hyperglycemia in type 2 diabetes, but also as an early metabolic abnormality that precedes the development of overt diabetes. The clinical definition of insulin resistance is the impaired ability of insulin (either endogenous or exogenous) to lower blood glucose. In some insulin-resistant individuals, insulin secretion will begin to deteriorate under chronic stress (glucose toxicity) and overt diabetes will result. If not, individuals will remain hyperinsulinemic, with perhaps some degree of glucose intolerance, together with other hallmarks of the IRS. The statistical correlation between hypertension and impaired glucose tolerance is clear, although the mechanism is not yet fully understood. Epidemiologic evidence of insulin resistance as an independent risk factor for atherosclerosis and coronary heart disease (CHD) completed the evolving concept of IRS as the common soil for the development of both diabetes and CHD. No single laboratory test exists for diagnosis of IRS. Rather, IRS remains a clinically evident syndrome that can be suspected on the basis of physical and laboratory findings. This identifies individual patients whom the clinician should screen for associated comorbid conditions, aggressively control cardiovascular risk factors, and tailor drug therapy for optimal benefit. This article provides practical guidelines to achieve these goals and specific strategies to ameliorate cardiovascular and metabolic risk in the IRS.     

Body Mass Index as a Guide for Diagnosing Prediabetes and Diabetes

The incidence of overweight and obese people has threatened the national healthcare system and the health of individuals who are at an increased risk of type 2 diabetes. An estimated one third of diabetes is undiagnosed in asymptomatic patients. This article describes how screening for prediabetes and diabetes can reduce both physical and financial costs and improve health care outcomes by early detection. A hemoglobin Alc (HbgAlc) can be cost effective through a single blood draw detailing the patient's average serum glucose over the previous 3 months. Electronic health records have the capacity to calculate body mass index, which could prompt HbgAlc screening.     

Behavioral science research in diabetes: lifestyle changes related to obesity, eating behavior, and physical activity

Lifestyle factors related to obesity, eating behavior, and physical activity play a major role in the prevention and treatment of type 2 diabetes. In recent years, there has been progress in the development of behavioral strategies to modify these lifestyle behaviors. Further research, however, is clearly needed, because the rates of obesity in our country are escalating, and changing behavior for the long term has proven to be very difficult. This review article, which grew out of a National Institute of Diabetes and Digestive and Kidney Diseases conference on behavioral science research in diabetes, identifies four key topics related to obesity and physical activity that should be given high priority in future research efforts: 1) environmental factors related to obesity, eating, and physical activity; 2) adoption and maintenance of healthful eating, physical activity, and weight; 3) etiology of eating and physical activity; and 4) multiple behavior changes. This review article discusses the significance of each of these four topics, briefly reviews prior research in each area, identifies barriers to progress, and makes specific research recommendations.     

Management of type 2 diabetes in youth: an update

Although type 1 diabetes historically has been more common in patients eight to 19 years of age, type 2 diabetes is emerging as an important disease in this group. Type 2 diabetes accounts for 8 to 45 percent of new childhood diabetes. This article is an update from the National Diabetes Education Program on the management of type 2 diabetes in youth. High-risk youths older than 10 years have a body mass index greater than the 85th percentile for age and sex plus two additional risk factors (i.e., family history, high-risk ethnicity, acanthosis nigricans, polycystic ovary syndrome, hypertension, or dyslipidemia). Reducing overweight and impaired glucose tolerance with increased physical activity and healthier eating habits may help prevent or delay the development of type 2 diabetes in high-risk youths. The American Academy of Pediatrics does not recommend population-based screening of high-risk youths; however, physicians should closely monitor these patients because early diagnosis may be beneficial. The American Diabetes Association recommends screening high-risk youths every two years with a fasting plasma glucose test. Patients diagnosed with diabetes should receive self-management education, behavior interventions to promote healthy eating and physical activity, appropriate therapy for hyperglycemia (usually metformin and insulin), and treatment of comorbidities.     

Cardiovascular disease in spinal cord injury: an overview of prevalence, risk, evaluation, and management

Cardiovascular disease is a growing concern for the spinal cord-injured (SCI) population. For long-term SCI, morbidity and mortality from cardiovascular causes now exceeds that caused by renal and pulmonary conditions, the primary causes of mortality in previous decades. Although risk estimates commonly used for ambulatory individuals have not been established from follow-up studies in SCI, nearly all risk factors tend to be more prevalent in SCI subjects compared with ambulatory subjects. These risks include a greater prevalence of obesity, lipid disorders, metabolic syndrome, and diabetes. Daily energy expenditure is significantly lower in SCI individuals, not only because of a lack of motor function, but also because of a lack of accessibility and fewer opportunities to engage in physical activity. Autonomic dysfunction caused by SCI is also associated with several conditions that contribute to heightened cardiovascular risk, including abnormalities in blood pressure, heart rate variability, arrhythmias, and a blunted cardiovascular response to exercise that can limit the capacity to perform physical activity. Thus, screening, recognition, and treatment of cardiovascular disease should be an essential component of managing individuals with SCI, and judicious treatment of risk factors can play an important role in minimizing the incidence of cardiovascular disease in these individuals. This article reviews the cardiovascular consequences of chronic SCI, including the prevalence of cardiovascular disease and risk factors unique to these individuals, and provides a synopsis of management of cardiovascular disease in this population.     

Lifestyle counseling for type 2 diabetes risk reduction in Dutch primary care: results of the APHRODITE study after 0.5 and 1.5 years

OBJECTIVE To study the overall effect of the Active Prevention in High-Risk Individuals of Diabetes Type 2 in and Around Eindhoven (APHRODITE) lifestyle intervention on type 2 diabetes risk reduction in Dutch primary care after 0.5 and 1.5 years and to evaluate the variability between general practices. RESEARCH DESIGN AND METHODS Individuals at high risk for type 2 diabetes (Finnish Diabetes Risk Score ≥13) were randomly assigned into an intervention group (n = 479) or a usual-care group (n = 446). Comparisons were made between study groups and between general practices regarding changes in clinical and lifestyle measures over 1.5 years. Participant, general practitioner, and nurse practitioner characteristics were compared between individuals who lost weight or maintained a stable weight and individuals who gained weight. RESULTS Both groups showed modest changes in glucose values, weight measures, physical activity, energy intake, and fiber intake. Differences between groups were significant only for total physical activity, saturated fat intake, and fiber intake. Differences between general practices were significant for BMI and 2-h glucose but not for energy intake and physical activity. In the intervention group, the nurse practitioners' mean years of work experience was significantly longer in individuals who were successful at losing weight or maintaining a stable weight compared with unsuccessful individuals. Furthermore, successful individuals more often had a partner. CONCLUSIONS Risk factors for type 2 diabetes could be significantly reduced by lifestyle counseling in Dutch primary care. The small differences in changes over time between the two study groups suggest that additional intervention effects are modest. In particular, the level of experience of the nurse practitioner and the availability of partner support seem to facilitate intervention success.     

Increased daily walking improves lipid oxidation without changes in mitochondrial function in type 2 diabetes

OBJECTIVE—To determine whether increased daily physical activity improves mitochondrial function and/or lipid oxidation in type 2 diabetes.RESEARCH DESIGN AND METHODS—Volunteers with (n = 10) and without (n = 10) type 2 diabetes were matched for habitual physical activity, age, sex, and weight. Basal and maximal mitochondrial activity, physical activity, and resting substrate oxidation were measured at baseline and after 2 and 8 weeks of increased physical activity.RESULTS—Baseline physical activity (6,450 ± 851 vs. 7,638 ± 741 steps/day), basal ATP use (12 ± 1 vs. 12 ± 1 μmol · ml⁻¹ · min⁻¹), phosphocreatine recovery from exercise (31 ± 5 vs. 29 ± 3 s), and basal lipid oxidation (0.57 ± 0.07 vs. 0.65 ± 0.06 mg · kg body wt⁻¹ · min⁻¹) were similar in people with and without type 2 diabetes. There was a significant increase in physical activity after 8 weeks (12,322 ± 1,979 vs. 9,187 ± 1,159 steps/day, respectively). Following increased physical activity, there were no changes in basal ATP use or phosphocreatine recovery after exercise in either group. Basal lipid oxidation increased after 8 weeks of increased physical activity in people with type 2 diabetes (0.79 ± 0.08 mg · kg⁻¹ · min⁻¹) but not people without (0.68 ± 0.13 mg · kg body wt⁻¹ · min⁻¹).CONCLUSIONS—Resting and maximal ATP turnover are not impaired in people with well-controlled type 2 diabetes compared with control subjects matched for physical activity as well as age and weight. Increased unsupervised daily physical activity is sustainable and improves lipid oxidation independent of change in mitochondrial activity in people with type 2 diabetes.The potential role of the mitochondria in the development of insulin resistance and type 2 diabetes has recently attracted much interest. Muscle biopsies taken from people with type 2 diabetes demonstrate smaller mitochondria and lower activities of oxidative enzymes compared with those of lean individuals without diabetes (1). Insulin-resistant people with a family history of diabetes have reduced basal mitochondrial activity in skeletal muscle compared with insulin-sensitive individuals (2). These observations, in combination with others (3–6), raise the possibility that mitochondrial defects could underlie type 2 diabetes. Defects in oxidative function could possibly help explain the impaired fatty acid oxidation (7) and elevated intramyocellular lipid (IMCL) (8) characteristic of impaired insulin action and type 2 diabetes. The elevated intramuscular lipid may affect insulin signaling in skeletal muscle (5), exacerbating insulin resistance.However, other studies have not observed abnormalities in basal mitochondrial activity in skeletal muscle of people with type 2 diabetes (9). Recent biopsy work has also shown that differences in oxidative enzymes between people with and without type 2 diabetes disappear when corrected for mitochondrial density (10). These data raise the possibility that type 2 diabetes is associated with normal mitochondrial function but that the mitochondrial capacity is reduced. This is an important differentiation, as it holds implications for the therapeutic approach to type 2 diabetes.People with type 2 diabetes are more sedentary than those without diabetes (11). It is clear that reversing this sedentary lifestyle with physical activity and/or exercise can produce significant improvements in long-term glucose control (12). These benefits could be mediated, at least in part, by changes in mitochondrial function (13). In people with type 2 diabetes, moderate-intensity exercise combined with moderate weight loss produced a significant improvement in insulin sensitivity and mitochondrial density (14). However, such moderate intensity exercise programs are difficult to implement and usually require close supervision. In contrast, unsupervised walking has been shown to produce significant improvements in long-term glucose control and is a sustainable behavior over long periods of time (2 years) (15). Little is known about how low-intensity physical activity interventions such as walking influence muscle metabolism in people with type 2 diabetes.This study was designed to 1) determine whether there are differences in basal and stimulated mitochondrial activity in people with type 2 diabetes compared with physical activity–matched control subjects and 2) establish whether an increase in daily physical activity is associated with changes in mitochondrial ATP turnover and changes in lipid oxidation.     

Correlates of physical activity in a sample of older adults with type 2 diabetes.

OBJECTIVE: Physical activity is integral to the management of type 2 diabetes. Unfortunately, the majority of adults with type 2 diabetes do not regularly engage in physical activity. The purpose of this study was to assess physical activity behavior and its correlates (i.e., physical activity knowledge, barriers, and performance and outcome expectations) in older adults with type 2 diabetes. RESEARCH DESIGN AND METHODS: A subgroup of 260 adults with type 2 diabetes was identified from a larger stratified random sample of adults aged > or = 55 years. Participants completed an interviewer-administered survey designed from focus group findings and social learning theory. RESULTS: The majority of the respondents (54.6%) reported 0 min of weekly physical activity. This was especially true of older female respondents. Performance expectation scores were lower among respondents who were in the oldest age-group, namely, white women. Physical activity knowledge varied by age-group, and barriers to physical activity were prevalent in all groups. The following are significant correlates of reported weekly physical activity: younger age, more education, fewer motivational barriers, and greater perceived health and performance expectations. CONCLUSIONS: Given the importance of physical activity to diabetes management, the low prevalence of physical activity found in this and other studies should raise concerns among clinicians. Future research to identify predictors of physical activity is needed to guide clinicians in the promotion of physical activity.     

Diet and exercise in the prevention of diabetes

The worldwide epidemic of obesity is being mirrored in worldwide epidemics of metabolic syndrome and of type 2 diabetes. The theme of the 2002 Future Forum conference is that these conditions are a certainty, given that the changing worldwide environment requires less physical activity for daily living and assures an abundant, energy-dense food supply at all times. This paper focuses on the roles of physical activity and weight reduction in reducing the risk for development of type 2 diabetes and the metabolic syndrome. The mechanisms by which obesity and detraining lead to insulin resistance and type 2 diabetes are discussed and, conversely, the mechanisms by which insulin resistance might be reversed by physical activity are addressed. Finally, the evidence from recent randomised clinical trials is reviewed. The Finnish Diabetes Prevention Study and the Diabetes Prevention Program in the USA both demonstrate that lifestyle change can significantly reduce the risk of development of type 2 diabetes in individuals with impaired glucose tolerance. Furthermore, these studies demonstrate that modest weight change and achievable physical activity goals can translate into significant risk reduction. Societies cannot afford to ignore the evidence of health benefit associated with physical activity and healthy weight in favour of medicating when morbidities develop. For a successful public health approach to chronic disease prevention, we cannot rely completely on pharmaceuticals, but must implement environmental changes to encourage healthy lifestyles.     

Self‐management practices of Chinese Americans with type 2 diabetes

The purpose of this study was to examine the level of diabetes self‐management and its association with demographic and diabetes‐related characteristics in Chinese Americans with type 2 diabetes. A questionnaire that measured diabetes self‐management and diabetes‐related characteristics was administered to a sample of 211 Chinese Americans with type 2 diabetes living in America. The results indicated that the participants were likely to take medications but less likely to carry out diet, physical activity, self‐monitoring of blood glucose, and foot care behaviors. Associations between diabetes self‐management and demographic and diabetes‐related characteristics were observed. For example, individuals who had less education and were employed were less likely to engage in diabetes self‐management than those with higher education and who were retired, while individuals who had a longer duration of diabetes and used insulin as a treatment more frequently carried out self‐monitoring than those who had a shorter duration of diabetes and used oral hypoglycemic agents. These findings indicate that the self‐management practices among the participants are suboptimal. Research on developing culturally and linguistically appropriate interventions to promote diabetes self‐management for Chinese Americans is warranted.     

Burden of disability in type 2 diabetes mellitus and the moderating effects of physical activity

The growing diabetic epidemic has created a substantial burden, not only on the people with diabetes but also on society at large. This mini-review discussed the limitations and patterns of disability in type 2 diabetes mellitus and put forward a case for the moderating effects of physical activity (PA) in the management of diabetes. The limitations and impairments associated with diabetes include vascular, neurological, cardiac, and renal impairments. Moreover, individuals participate less in their daily lives and in their instrumental activities of daily living, which negatively impacts the quality of life of individuals with diabetes. This often leads to a loss of quality of life due to disabilities, resulting in an increased rate of disability-adjusted life years among people with type 2 diabetes mellitus. Moreover, there are psychosocial sequelae of diabetes mellitus. This necessitates looking for moderating factors that may reduce the burden of the disease. PA has been shown to be one of the factors that can mitigate these burdens. PA does this in several ways, including through the benefits it confers, such as a reduction of hemoglobin A1c, a reduction of excess fat in the liver and pancreas, and the reduction of cardiovascular risk factors, all of which favorably affect glycemic parameters. Specifically, PA regulates or moderates diabetes disability through two mechanisms: The regulation of glucolipid metabolism disorders and the optimization of body mass index and systemic conditions. Therefore, efforts should be directed at PA uptake through identified strategies. This will not only prevent diabetes or diabetes complications but will reduce its burden.