By Louise Lazear
Controlling the obesity epidemic is simple in theory, but as complex to manage as human behavior
Even as you read this, the world’s population is on the rise, increasing in both number and girth. According to the World Health Organization, obesity in industrialized and developing countries has increased 50 percent over the last seven to ten years. In the year 2000, an estimated 300 million people across the world suffered from obesity, up from about 220 million in 1995. According to the 1999 National Health and Nutrition Examination Survey of 1999, almost 61 percent of U.S. adults are overweight or obese, with rates of obesity doubling from 15 percent in 1980 to 27 percent in 1999. And obesity in children has increased by more than one percent per year over the last ten years, with estimates of $99 billion in future health care costs looming for our country alone.
Obesity is the second leading cause of preventable death in the U.S. The inherent risks associated with being overweight or obese are well documented and include hypertension, dyslipidemia, coronary heart disease, stroke, and endometrial, breast, prostate and colon cancers. Obesity has been identified as the major culprit in the increased incidence of type 2 (non-insulin dependent) diabetes in adults and especially children, where this type of diabetes has reached epidemic proportions. And one cannot overlook psychological disorders and the impact of social stigmatization and discrimination associated with this disease.
Most scientists and clinicians agree that obesity is caused by a fusion of environmental and genetic factors. The social and cultural aspects of modern life, human behavior, metabolism, physiology and genetics have all been implicated in the development of obesity. But its sharp increase has alarmed public health officials and scientists worldwide, and professionals from a wide range of disciplines are searching for its cause as well as treatment and prevention. “One thing that is clear to many people is that the rapid increase in obesity is part of a larger picture,” said Marquisa LaVelle, Ph.D., a biological anthropologist and organizer of a symposium on worldwide obesity held at the American Association for the Advancement of Science meeting held in Boston earlier this year. “This rapid change cannot be explained by a lack of personal willpower or changes in the human gene pool because it is happening so fast and has become so widespread,” she stated. According to LaVelle, the epidemic is associated with a transition to industrialized lifestyles, and is part of a trend in increased height and weight and earlier puberty in children. “In the U.S., the increase in stature has leveled-off over the last twenty years, but increases in body weight and decreases in muscle mass are ongoing. From an anthropological point of view, this indicates not only changes in worldwide food supply and the commercialization of food, but sedentary living.”
While LaVelle and her colleagues focus on social and cultural clues for the epidemic, others are unraveling the genetic and hormonal links to obesity. To date, no specific gene has been identified as the sole cause for weight gain and obesity. However, researchers in Dallas recently discovered that mutations in the AGPAT2 gene cause congenital generalized lipodystrophy (CGL), a disorder characterized by partial or complete lack of body fat at birth. Children diagnosed with CGL often develop severe diabetes and other complications including high blood lipids and fat accumulation in the liver. While extremely rare and affecting only one in 12.5 million people, mapping the genetic mechanism behind CGL may ultimately lead to a further understanding of obesity and related diseases. Elsewhere, researchers in Boston identified a protein that enables the body to overcome resistance to leptin, the hormone that signals the brain that the body is satiated after food consumption. Because obese individuals have high levels of leptin and can also exhibit leptin resistance, scientists hope that further study of the protein may eventually lead to drug therapies for treatment and prevention of obesity.
While this research offers promise in unlocking the key to obesity, clinicians on the front line point to nutrition and lack of physical activity as prime contributory factors to disease development. “It seems clear that the over-abundance of very tempting, high-calorie, cheap, well-prepared food and the over-abundance of very cheap gasoline is responsible for the epidemic in our country, “said Francis A. Neelon, M.D., endocrinologist and staff physician at the Rice Diet Program at Duke University Medical Center. “Are there genetic links? Of course, genes are what causes one to eat this way. But I am not aware of any genetic links that we can sort out at the moment. Eventually, we will. Leptin resistance is a very interesting hypothesis. It may play a role, but it is just one part of a very complicated series of control mechanisms relating to eating behavior. It comes down to the fact that we do have these ‘pushes’ to eat, and we have a country with an economy that is driven by satisfying those desires,” Neelon added.
Currently, there are no diagnostic or predictive biomarkers for overweight or obesity. According to Neelon, obesity is most often diagnosed statistically and clinically, where even small weight gains in combination with other associated diseases could be classified as morbid obesity. “The best statistical method (to define obesity) is the body mass index (BMI) which has been very well validated. There are some exceptions to the rule, but they are few and far between. There are other subtle ways to determine obesity, for example percentage of body fat which can be measured by underwater weight, and other complicated methods that are expensive and don’t add a lot to the diagnosis,” he said.
“The best diagnostic is the scale and history of weight gain,” echoed Walter Willett, M.D., Dr.P.H., chairman of the department of nutrition at the Harvard University School of Public Health and author of Eat, Drink, and Be Healthy.
“Physicians and patients need to address weight gain early before actual overweight or obesity occurs. We need to pay attention to even six to eight pound weight gains during mid-life, as this indicates an energy imbalance that will only get worse. Pharmaceutical interventions now available will play only a modest role. Regular exercise and attention to excessive calories will be most important. Most physicians will probably appropriately refer patients to weight control programs, but they themselves can also provide essential information and motivation.” Some of Willett’s ideas run counter to the adopted standard of proper nutrition, including the food pyramid. “We collectively made a serious mistake by heavily promoting low-fat, high-carbohydrate diets as a solution to weight problems. The public was led to believe that only fat calories would lead to weight gain, but the evidence is clear that excessive calories from starch, sugar, or fat will all make us fat.”
To help physicians address these issues with their patients, in 1998 the National Heart, Lung and Blood Institute (NHLBI) published guidelines that address assessment of and treatment for obesity. Assessment includes determination of BMI, waist circumference, and the presence of associated diseases. BMI, which is defined as weight in kilograms divided by the square of height in meters, has a high correlation with total body fat content. According to the NHLBI guidelines, adults with a BMI greater than or equal to 25 are considered at risk for premature death and disability. Those with a BMI of 25 to 29.9 are classified as overweight, and those at 30 or above are considered obese. While health risks increase with higher BMI, it has been found that weight loss in both obese and overweight patients can reduce risk factors for diabetes and cardiovascular disease with associated reductions in blood pressure, serum triglycerides, and blood glucose.
Waist circumference and more recently waist-to-hip ratios (WHR) are also used as independent predictors of risk factors and diseases associated with obesity with some exceptions. Risks associated with waist circumference measurements differ by sex: men are considered at risk with measurements greater than 40 inches, while the cut-off for women is at 35 inches. The waist-to-hip ratio reflects where the weight is carried: according to the CDC, extra abdominal fat carries more risk than fat carried in the hips and thighs. Interestingly, researchers reported at the annual American Academy of Neurology meeting that WHR may be a better predictor of stroke than BMI, and may be even more relevant in predicting stroke in persons classified as normal and overweight, versus those considered to be obese.
Neelon and his associates at the Rice Diet Program use BMI as well as conventional laboratory studies to assess patients and monitor therapeutic progress. A typical work-up for weight loss includes a thorough history and physical, with a focus on hormonal disorders, CVD, sleep apnea or snoring, and arthritic or pulmonary conditions. Routine laboratory evaluations include blood count, blood chemistries, lipid status, thyroid function and glucose metabolism. Patients are then placed on an 800 to 1,000 calorie per day diet that restricts fat, sodium, and protein. Diets are altered as weight is lost, and protein levels are eventually increased with vegetables and occasionally meat. While recognizing the value of pharmaceutical intervention, Neelon favors a different approach. “This program has a very intense medical focus, and our goal is to remove as many medications from people’s lives as we can.”
Pharmacotherapy for treatment of obesity remains a viable option for some patients. However, the withdrawal from the market of dexfenfluramine and fenfluramine due to a reported association with valvular heart disease has led to increased scrutiny of these drugs. In March 2002, Public Citizen filed a petition with the FDA to remove the obesity drug Meridia (sibutramine) manufactured by Abbott Laboratories from the market, claiming issues of safety and efficacy. In a statement issued by Abbott, the company stands behind the original FDA approval granted in 1997, and reiterates its position that along with diet and exercise, Meridia can contribute to weight loss and the consequent health benefits. According to a spokesperson, Abbott has additional therapeutic drugs for obesity in the development pipeline.
Typically reserved for patients who have failed at other measures, gastric bypass surgery may also be an option in the fight against morbid obesity. “Absolute requirements are at least 100 pounds over ideal body weight, or a BMI of 35 with a significant co-morbidity, such as severe diabetes, or a BMI of 40 without some co-morbidity. However, most patients at this point have associated disease related to their weight, whether joint problems or some other disability,” said Kenneth G. MacDonald, Jr., M.D., bariatric surgeon and professor at the Brody School of Medicine at East Carolina University. According to MacDonald, gastric bypass surgery, which was first performed in the 1970s, has increased in popularity as a treatment for morbid obesity. MacDonald and his colleagues perform a procedure called the Roux-en-Y gastric bypass, where approximately 20 cc of the proximal stomach is stapled together, forming a pouch. The remaining stomach tissue is also stapled, and pouch and stomach are surgically separated. The small intestine is severed and the distal portion is attached to the pouch. The proximal end is reattached to stomach, so that secretions from the stomach and pancreas can empty into the small intestine and mix with food. The procedure can be performed laparoscopically, and patients are typically released from the hospital two or three days post surgery. After several days, patients are placed on a simple low-fat diet that stresses solid food limited to three meals per day. Post-surgical approaches to patient management can vary. At ECU, patients are followed by their surgeon and are seen frequently during the year following surgery, and then once or twice a year at which time they are evaluated for albumin levels, B-12 deficiency and anemia. “Patients generally reach levels of 70 to 75 percent excess weight lost between one or two years after surgery. In a long-term follow-up of our patients, the mean excess weight lost is 50 percent at ten years and on into sixteen and seventeen years post bypass,” said MacDonald. Reasons for weight gain over the course of a patient’s life depend on both lifestyle and physiology. “The gut adapts, and is remarkably efficient at absorbing calories. In addition, a small amount of dilation can occur in the anastomosis, allowing the patient to eat more food over time,” MacDonald added.
Despite advancements in both pharmaceutical and surgical approaches to obesity and weight management, many believe that real solutions will require heightened public awareness and difficult, expensive changes in public policy. “I think that the issue of obesity is so embedded in our culture that only a very multifaceted approach will be effective, and everyone will need to play a role,” said Willett. “School nutrition and physical activity programs need enhancement almost everywhere, and the physical environment of cities and towns need to be improved to promote safe walking and biking. Worksites need incentive programs to promote good diet and regular activity, and parents will need to play a more active role in limiting TV and setting an example,” he added. Perhaps we can begin the process at the individual level in hopes that others will follow. Skip dessert, take the stairs and go for a walk instead of catching The Sopranos. Before you know it, the world will seem a lot lighter place to be, and those jeans that seemed to have shrunk while hanging in the closet may actually fit again.
Louise Lazear is a freelance writer in Charlotte, N.C.