Is Obesity A Disease or A Behavior Abnormality? Did the AMA Get It Right?

In June 2013, the American Medical Association (AMA) House of Delegates voted to recognize obesity as a disease state requiring treatment and prevention efforts. A number of other medical societies had sponsored a resolution to support this idea, including the American Association of Clinical Endocrinologists, the Endocrine Society, the American College of Cardiology, the American College of Surgeons, and the American Heart Association. The National Institutes of Health had declared obesity a disease in 1998 and the American Obesity Society did so in 2008. Because the AMA is thought of as the most influential medical association in the country, their statement is expected to have a significant influence on health care policy, through effects on insurers, industry, and lawmakers. The stated purpose for this decision is to improve research into the causes of obesity, leading to improvement in methods to prevent and treat it, ultimately improving patient health and outcomes. This decision would be expected to improve insurance coverage and reimbursement to providers for treating individuals with obesity. In addition, this change in public policy by the AMA supports the concept that obesity is a serious disease that requires treatment and also removes the stigma currently associated with obesity (i.e., it is not just a poor lifestyle choice).

The AMA decision is controversial, since the AMA’s own Council on Science and Public Health in 2012 said that there was not sufficient data to support calling obesity a disease. In this article I will discuss some of the issues associated with this controversy, as well as what we know regarding the etiology of obesity. I will then return to the discussion of whether designating obesity as a disease is an appropriate decision.

Obesity as a Leading Heath Problem

According to the American Heart Association, obesity is found in almost one-third of U.S. adults and 17% of U.S. children ages 2 to 19. Worldwide it was estimated in 2010 that there are approximately 500 million obese people and another 1.4 billion who are overweight. The number of obese individuals is estimated to rise to 700 million by 2015.¹ Obesity is estimated to cause approximately 112,000 to 365,000 deaths per year. Its prevalence has increased since the 1970s in the U.S. (data from NHANES II and III) and in Europe.² This increase has occurred across every age group, sex, race, and smoking status.³

Advertisement showing young woman with package of Loring’s Fat-Ten-U food tablets and package of Loring’s Corpula, a fat-producting food. Circa 1895

Obesity is recognized as a significant public health hazard, as it increases the risks for multiple diseases, such as type II diabetes, cardiovascular disease, hyperlipidemia, hypertension, stroke, breast and colon cancer, and degenerative arthritis.⁴ The cost of treating obesity related conditions are estimated to range from 147 to 210 billion dollars per year. It decreases quality of life, functional capacity, and increases morbidity and mortality. Treatment has been shown to reduce morbidity and mortality.⁵ Therefore, preventing or treating obesity would be very beneficial on both an individual and societal basis.

One of the controversies regarding whether to define obesity as a disease is the fact that there is not agreement as to the definition of obesity. Obesity can be defined as an excess of body fat that leads to increased morbidity and mortality. From an epidemiological standpoint, it may be defined as a BMI of greater than or equal to 30 kg of body weight per meter squared.² This is a simple and easy to use calculation, as the data are readily available. The BMI is considered a marker for adiposity and is widely used to predict and evaluate disease risk. It is not an ideal measure, as it does not account for variations in body composition. Other methods to measure body fat and composition include waist circumference, skin fold thickness, waist to hip ratio, waist to height ratio, bioelectrical impedance, and dual energy X-ray absorptiometry. These metrics or techniques are not consistently available in all settings. In 2012 the AMA Council argued that the lack of a universally agreed upon metric limits the ability to define obesity as a disease and therefore, calling it a disease would not improve health outcomes.

Can Obesity Ever Be ‘Healthy?’

It is known that some people with a BMI in the obese range are putatively ‘healthy,’ and some with a normal BMI have an excess of visceral body fat and are not healthy. There is also the “obesity paradox.” It appears that some people with a BMI in the obese or overweight range have better short- and long-term health outcomes than those with a normal BMI. Research suggests that the “obesity paradox” may have been due, in part, to the level of physical fitness of the individual. Those persons with a higher fitness level have the more favorable prognosis.⁶ A more recently study⁷ provides evidence that the “obesity paradox” is not true. This meta-analysis investigated the association of BMI, metabolic status, and cardiovascular events and total mortality. The result of this study was that obese individuals, regardless of their metabolic status (healthy or unhealthy) were at increased risk for adverse health outcomes, when compared to individuals of normal weight. This risk was seen only in the studies with more than 10 years of follow-up.

This study, and the accompanying editorial,⁸ support the concept that obesity increases risks for adverse health outcomes, and should be considered a disease. AACE⁵ and others⁹ argue that the epidemiologic evidence supports the association of excess body fat with risks for other primary diseases, such as diabetes, hypertension, hyperlipidemia, and coronary artery disease. The lack of a universal metric should not preclude calling obesity a disease.

Is Obesity a Disease?

A related and more challenging controversy is whether obesity meets the definition of a disease. To discuss this, we need to agree on the definition of a disease, which is not as obvious as it would seem. Historically, it has long been recognized that people who are overweight or obese were at higher risk of sudden death; this dates back to Hippocrates over 2500 years ago. More recent historical comments, from 1600 through 1934, demonstrate that many observers thought that “corpulency” was a disease in some but not all cases, which could lead to increased morbidity and mortality in some cases.⁹

Corpulent Quotes 1600s–1934.

“Corpulency may be ranked amongst the diseases arriving from original imperfections in the functions of some of the organs, yet it must be admitted also, to be most intimately connected with our habits of life.”

-Thomas Sydenham, 1624–1689

“Corpulency, when in an extraordinary degree, may be reckoned a disease, as it in some measure obstructs the free exercise of the animal functions; and hath a tendency to shorten life, by paving the way to dangerous distempers.”

-Malcolm Flemyng, 1760

“The only disease to be mentioned in this chapter, I have, with other nosologists, named Polysarda; and in English it maybe named Corpulency, or, more strictly Obesity…This corpulency or obesity, is in very different degrees in different persons, and is oft en considerable without being considered as a disease. There is, however, a certain degree of it, which will be generally allowed to be a disease; as, for example, when it renders persons, from a difficult respiration, uneasy in themselves, and, from the inability of exercise, unfit for discharging the duties of life to others: and for that reason I have given such a disease a place here.”

-W. Cullen, 1808

“Fat is, of all the humors or substances forming part of the human body, the most diffused; a certain proportion of it is indicative of health, and denotes being in good condition – nay, is even conducive to beauty; but when in excess – amounting to what may be termed OBESITY – it is not only in itself a disease, but may be the cause of many fatal effects, particularly in acute disorders.”

-W. Wadd, 1810

“Corpulency, when it arrives at a certain height, becomes an absolute disease.”

-Robert Thomas, 1811

“That many persons never become corpulent, no matter what they may eat, is undoubtedly true. These remarks are not for them but for those whose habits of living have produced that degree of obesity which if it does not render life a burden, begets in him who is afflicted with it (for it is almost a disease) a state extremely uncomfortable, sometimes painful, and always mortifying.”

-E. Price, 1867

“Obesity in man is oft en an infirmity, and sometimes a grave disease.”

-Anonymous, 1886

“The accumulation of fat in the tissues, or obesity, is a pathological or diseased condition.”

-Wood, 1893

“Obesity is not itself a disease in all instances.”

-W.G. Campbell, FDA Chief, 1935

There is not one agreed upon definition of a disease. I have chosen several as representative examples. Kincaid⁹ states that disease is deviation from species-typical functioning; disease is deviation from the average. In the evolutionary function view, disease occurs when an organ is not performing the job that allowed it to evolve by natural selection.

A more widely held definition is that of Heshka and Allison;¹⁰ theirs is an extraction of four points common to definitions from multiple general language and medical dictionaries:

1. Disease is a condition of the body, its parts, organs, or systems or an alteration thereof.

2. It results from infection, parasites, nutritional, dietary, environmental, genetic, or other causes.

3. It has a characteristic, identifiable, marked group of signs or symptoms.

4. It deviates from normal structure or function (variously described as abnormal structure or function; incorrect function; impairment of normal state; interruption, disturbance, cessation, disorder, derangement of bodily or organ functions).

Definitions from the FDA in 1993, Downey and Conway (2001), and Rene (2004)⁹ share some but not all of these criteria. In 2007, the AMA stated that criteria 1, 2, and 4 were necessary for a condition to be called a disease. At that time, it stated that obesity did not meet the criteria to be considered a disease.⁹ Several of these authors, as well as the AMA Council in 2012, did not think obesity met the definition of a disease. Conversely, AACE, in a 2012 position statement, stated that obesity met these three conditions.⁵ The AACE position probably stems from differences of opinion in the definition of a disease, how to apply those definitions, and which facts regarding obesity fit which definition. As there is no universally accepted definition of a disease, it is possible that one cannot have a scientific, definitive answer regarding obesity. The American Obesity Society⁹ suggested that since there is no clear definition of a disease, it does not make sense to ask if obesity is a disease. They do support calling obesity a disease based on a utilitarian approach to public health.

The epidemic of obesity and its associated complications are challenging the world’s health care system and might slow or even reverse the life expectancy gains of the last 50 years. Understanding its multiple causes would help in the development of effective preventions and treatments. Obesity is a complex condition with many causes. In general, obesity results from an imbalance between energy consumption (dietary intake) relative to energy expenditure (energy used in metabolic and physical activity). People gain weight because energy intake exceeds expenditure, i.e., positive energy balance. There are multiple potential contributing factors to this imbalance including genetic, environmental, behavioral, physiologic, psychological, social, and economic.³

Twin and adoption studies show that variations in BMI have a significant genetic component, and it has been estimated that these genetic effects contribute as much as 70% of the variation in obesity. These effects may contribute to obesity via effects on energy intake, expenditure, and abnormal regulation of satiety signals.¹ Rare, simple genetic defects such as leptin deficiency or MC4R abnormalities have clearly been shown to cause obesity. More common gene variations seem to have a small effect size on weight, and no single widespread gene has been found that can explain obesity. It is likely that multiple genes are involved in the heritability and susceptibility for obesity.^{1, 11, 12}

Why is Obesity More Prevalent?

Environmental influences are another major contributor to obesity.^3,11,12,13 The so-called “obesogenic” environment with its reduced food costs, the especially plentiful high calorie dense foods, larger ser ving portions, reduced physical activity, and the influential food industry, are likely contributors. U.S. government food policies in the 1970s are also thought to be a contributor to obesity. Other environmental contributors include endocrine disrupters (industrially produced chemicals such as plastics) that can disturb endocrine function. The most widely studied of these is bisphenol A. Sleep deprivation, medications, social networks, stress, and changes in bacteria in the GI tract (microbiome) are thought to be contributing factors. It has been suggested that obesity is a biologic adaptation to this obesogenic environment,¹⁴ or that it is a chronic relapsing neurochemical disease.¹⁵ Epigenetics has been proposed as a possible link between the complex interplay of both genetic and environmental factors in regulation of energy intake, expenditure, and energy balance. ¹⁶

There are multiple contributing factors for obesity, as well as many unanswered questions. If the environment promotes obesity, why is everyone not obese? Why do some people eat more than others? It is known that simply trying to increase calorie expenditure as a method of weight reduction does not consistently work. Studies have shown that losing fat mass can have adverse effects on appetite control and even reduce energy expenditures, making further weight loss even more difficult.¹⁴ The contrarian food writer, G. Taubes,¹⁷ as well as Hebert,⁶ think that the energy balance hypothesis is incorrect, and that this has adversely influenced research and policy decisions on prevention, treatment, and public health. Both suggest further research into the causes of obesity.

What Good or Bad Effects Might Come From Calling Obesity a Disease?

So is it a good idea to label obesity a disease? Overall, I think yes it is despite the many controversies associated with the disease designation. These include the controversy regarding the lack of a universal definition for obesity, and whether it fits the scientific definition of a disease. There are also concerns that the definition of obesity as a disease will shift the emphasis towards treatment with surgery/medications, and away from prevention efforts via lifestyle changes, including behavior modification, diet, and exercise. There are concerns that obese people will be labeled as having a disease, even if they are not sick. This could have effects on obese individuals’ efforts to manage their weight and make lifestyle changes.

The position of the AMA, AACE, Obesity Society, and other medical organizations is that obesity and its related diseases have a significant adverse effect on public health. This designation will focus society on the importance of preventing and treating it. A designation of obesity as a disease that results from a complex interplay of behavioral, environmental, and genetic factors should shift the stigma and discrimination from considering it as simply a lifestyle issue of poor eating habits and sedentary lifestyle.

In our society, labeling it as a disease would be expected to improve attitudes and financial support for obesity treatment. This would include more resources for health promotion, research into the behavioral, environmental, and genetic causes, as well as prevention and treatment (medical and surgical). This would improve insurance coverage and reimbursement for screening, health promotion, prevention, and treatment.

Obviously obesity is a complex topic. Despite extensive research, the causes for this disease are not well understood and good treatment options remain elusive. As Dr. George Bray, a distinguished obesity researcher, once said, “Obesity isn’t rocket science, it’s much more complicated.”¹³

Biography

Howard Rosen, MD, MSMA member since 1990 and Missouri Medicine Editorial Board Member for Endocrinolgoy, practices in North Kansas city and specializes in Endocrinology, Diabetes & Metabolism.

Contact: secretary@nkcendo.com