Shelby Rush, M.D. FACSM, is a full-time faculty member at Natividad Family Medicine Residency Program in Salinas, CA, and is assistant clinical professor at the University of California, San Francisco Department of Family and Community Medicine. She coordinates the orthopedic and sports medicine curricula at Natividad Medical Center where she has a sports medicine clinic. Dr. Rush completed a fellowship in sports medicine at The Orthopedic Specialty Hospital in Salt Lake City, UT. She is board certified in Sports Medicine and Family Practice. Dr. Rush is a physician for the U.S. Ski & Snowboard Association and a team physician for Hartnell College and North Salinas High School. She also was a member of the medical team for skating events at teh 2002 Olympic Games.
In 1980, approximately 15% of Americans were obese; now, one in every three adults is obese. The incidence of childhood obesity is growing at an alarming rate too. Along with obesity come many adverse health affects. People with obesity have increased the incidence of glucose intolerance, diabetes, hypertension, elevated blood cholesterol and triglycerides, polycystic ovary syndrome, and heart disease. Along with these adverse health conditions go increasing health-care costs. According to the American Diabetes Association, diabetes health care cost the United States $132 billion in 2002. Annual per capita health-care expenses average $4,000 for people with diabetes but without cardiovascular disease, and $10,000 for those patients with cardiovascular effects.
One result of obesity is insulin resistance (Table 1). A few individuals have been identified as having inherited problems with insulin receptors, glucose transport, or intercellular signals, but most people with insulin resistance have acquired the problem. Lifestyle problems that lead to insulin resistance are inactivity, overeating, aging, certain medications, eating high-sugar foods, and eating foods with a lot of fat. As a result of decreased muscle use of the excess energy and persistent high-energy intake, specifically in the form of simple sugars, the body makes excess insulin. This insulin saturates the insulin binding sites in muscles and adipose (fat cells) tissue, leading to storage of the excess energy. With time, the cells of the pancreas that manufacture insulin become burned out, and they do not make as much insulin. This means the body does not have its normal marker of the energy intake and cannot use energy as efficiently. The muscle cells cannot absorb as much sugar, and the liver tries to make more sugars from proteins and to store more energy as fats. During this stage, excessive sugar intake is lost in the urine, and people become used to having the sugar "high" in the brain. This sensation is important to remember when counseling people with noninsulin-dependant diabetes or insulin resistance during exercise or weight loss. Because the brain can adapt to blood glucose levels of 300 mg/dL or higher, normal amounts of 100 to 120 mg/dL or the resultant decrease in circulating sugars associated with exercise may make people feel like they are going to pass out or that their blood glucose level is dangerously low. The immediate response is to drink a soda or eat a candy bar to get their sugar "normal." Have clients monitor their blood glucose and reassure them that what they are feeling is normal as long as their blood sugar is higher than 70 mg/dL.
In the 1980s, the associated risk factors of insulin resistance and diabetes were grouped together and termed Syndrome X. Today, the classification of metabolic abnormalities associated with obesity and the resultant adverse health affects have been renamed the metabolic syndrome. As listed in Table 2, the diagnostic criteria for the metabolic syndrome are three or more of the risk factors and do not have to include diabetes or impaired glucose tolerance. However, the morbidity and mortality is greater for people who do have elevated blood sugars, regardless of other risk factors. Recently published articles reviewing pharmacologic intervention in the various risk factors of the metabolic syndrome show that control of blood glucose results in a greater reduction of morbidity and mortality than control of any of the other factors. To date, no studies to my knowledge have compared impaired glucose tolerance morbidity and mortality to the risks associated with tobacco use, but it would be interesting from a public health perspective. Given the prevalence of fast food chains and the high volume of unhealthy foods accessible to the public, if the risks of isolated insulin resistance equal those of smoking, are the food manufacturers and fast food restaurants then responsible for the associated health-care costs? Most states have won large awards from the tobacco manufacturers to offset the public health-care costs related to tobacco.
Although the epidemic is growing, the good news is that lifestyle changes and dietary and exercise intervention can reverse the metabolic syndrome. Even short-term weight loss improves insulin sensitivity. Weight loss also lowers low-density lipoprotein cholesterol. Exercise and increased activity increase high-density lipoprotein cholesterol and lower the very low-density lipoprotein cholesterol. Weight loss and exercise both lower circulating trigylceride levels. Together, these effects lower cardiac risk factors. Increased activity also can help to lower blood pressure.
Dietary counseling is very important with the metabolic syndrome. People need more than just the Zone or Atkins diet. They need to learn healthy food choices and proper caloric intake for weight loss. They need to change their lifestyles so that they can maintain their ideal weight once it has been achieved. More importantly, they need to maintain healthy food choices and remain active to prevent insulin resistance, the metabolic syndrome, and the resultant health problems associated with obesity. Although the Atkins diet may initially help people with insulin resistance, the weight loss associated with any diet is a factor of energy intake versus energy expended. People need to learn how to measure and adjust their caloric intake. After a year, the Atkins diet does not offer any advantage over other forms of diet. Because the brain only can use sugar for energy, if the daily intake of simple or complex sugars is restricted, then the liver will convert proteins into sugar. Therefore, the best diet is one that clients can maintain for a long time. This means making it socially and ethnically appropriate for each individual client. Again, clients need to understand food calories and how to adjust their caloric intake for the rest of their lives.
Another dietary change that can help with the metabolic syndrome is lowering the fat content, especially saturated fats. Many people are misled into thinking that foods labeled as "low fat" or "fat free" in the supermarkets do not have any fat. Many manufacturers claim their foods have no fat when the foods contain free fatty acids, or the backbones of dietary fat. Simple instruction in how to read and interpret the ingredients will help clients ascertain what is really low in fat. Because of the increased cardiovascular risk associated with saturated fats, clients can learn to choose polyunsaturated foods and how to prepare foods in a healthier manner. Clients with hypertension, or high blood pressure, can often benefit from low-sodium, or low-salt, diets. Again, many clients are not aware of the high sodium content of prepared foods. Even packaged breakfast cereals and breads are high in salt. Simple education can result in dietary modification, with a resultant decrease in blood pressure.
Probably the biggest lifestyle adjustment for people with the metabolic syndrome is activity. Exercising muscle uses and stores sugars better. As the muscles take up more sugar, the pancreas needs to manufacture less insulin, thereby making the body's circulating insulin level lower. In turn, the negative effects of high blood insulin are reversed, making the body more sensitive to the insulin it makes. Whether clients are insulin resistant, meet the criteria for the metabolic syndrome, or have diabetes, they will benefit from the lowered circulating blood sugar associated with exercise. As mentioned previously, people with diabetes often feel faint when they start exercising. This is a result of the lowered blood glucose but usually is not dangerous. Make sure clients can check their blood sugar and are aware of their medications (Table 3). As with all health problems, clients need to discuss their exercise regimen with their doctor and make sure they can begin exercise safely.
When diet and exercise fail to control insulin resistance and the metabolic syndrome, a physician may start clients on medications. The current first-line agent used for people with impaired glucose tolerance is metformin. Metformin is an oral agent used in the treatment of type 2 diabetes mellitus. It acts primarily by decreasing the body's sugar production and by making tissues more sensitive to circulating insulin. It does not result in low blood sugar levels. As opposed to other oral agents for the treatment of diabetes, metformin does not result in weight gain and has a positive effect on trigylceride and low-density lipoprotein cholesterol levels, thereby decreasing cardiovascular risk. It can improve the elasticity of small blood vessels, reducing other risks associated with high blood sugars. Metformin is available in generic forms, meaning a lower cost to clients.
Recently, the thiazolidinediones (TZD) were introduced for the treatment of diabetes and the metabolic syndrome. These medicines reduce insulin resistance in all cells. They work at the nuclear level to ensure the proper cellular manufacture of insulin receptors, regardless of circulating sugar levels. Their mechanism of action helps to keep the blood sugar and insulin levels low. TZDs positively affect high-density lipoprotein cholesterol but do not impact cardiovascular risk levels based upon cholesterol ratios. The vessels are more pliable with TZDs, resulting in lower blood pressure, less renal disease, and lower risk of heart attack.
In summary, when working with obese clients, a routine measure of abdominal circumference can assist in referral for proper evaluation and treatment of the metabolic syndrome. Some clients might be resistant to starting pharmacologic intervention, but simple reassurance of the safety of the medications and reference to the benefits might prevent long-term effects of insulin resistance and high blood glucose. For all clients, reinforce dietary and lifestyle changes that can reduce their morbidity and mortality. Most importantly, identify lifestyle adjustments the client can incorporate for the long run.
American Diabetes Association. Standards of medical care for patients with diabetes mellitus. Diabetes Care 26 (suppl):S28-S32, 2003.
Mayerson, A.B., R.S. Hundal, S. Dufour, et al. The effects of rosiglitazone on insulin sensitivity, lipolysis, and hepatic and skeletal muscle triglyceride content in patients with type 2 diabetes. Diabetes
Mokdad, A.H., E.S. Ford, B.A. Bowman, et al. Prevalence of obesity, diabetes, and obesity-related health factors, 2001. Journal of the American Medical Association 289:76-79, 2003.