Tuesday, June 17, 2008

The Other Side of the Obesity as Disease Debate

Obviously the debate about classifying obesity a disease is not a new idea, for years various researchers, special interest groups and organizations have debated the merits of defining obesity as a disease, with each round of reasoning and review of the evidence leading to the determination that obesity is not a disease unto itself, leaving it to remain categorically a health issue - a risk marker and a condition one is better to address than to ignore, but not a disease in need of specific medical intervention per se, but a condition with treatment options at the discretion of those within the medical community treating obese patients.

This distinction is important - while medical interventions are available, they are not the sole option for those who are obese; nor are all individuals with a BMI of 30 or greater automatically deemed to have a chronic disease in need of treatment by licensed healthcare professionals. If someone is obese, they are clearly able to seek medical treatment if they desire that option, just as they can opt instead to join Weight Watchers, read and follow the South Beach Diet on their own, or, gasp!, do nothing if their obesity is not causing them other health problems.

In order to fully understand the implications of the current position foisted in the Obesity Society white paper, it's important to look at the arguments as they've developed over the years. One exceptionally well written paper was published in October 2001 in the International Journal of Obesity - Is Obesity a Disease?

In that paper, the authors take time to review and discuss the "characteristics of obesity to determine if they fit the common and recurring elements of definitions of disease." They utilize a sample of definitions of disease taken from "authoritative English language dictionaries" to determine a common understanding of what defines "disease" and from there, examine if obesity fits the definition.

They tell us, "we identified the following common and recurring components:

(a) a condition of the body, its parts, organs, or systems, or an alteration thereof;
(b) resulting from infection, parasites, nutritional, dietary, environmental, genetic, or other causes;
(c) having a characteristic, identifiable, marked, group of symptoms or signs;
(d) deviation 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)

Then ask, "[h]ow well does obesity fit the definition of disease?"

Using the above criteria for disease, they evaluate whether defining obesity as a disease can be accomplished within the definition of disease.

There should be little disagreement that obesity satisfies conditions (a) and (b) above. That is, (a) an excess accumulation of fat can certainly be thought of as a condition of the body, and as for (b), the list of potential causes is so extensive that the causes of obesity must surely be found there.

Condition (c) poses a problem. Indeed, obesity can be diagnosed visually from physical proportions, or with the help of height and weight measurements. In cases of doubt, body composition methodologies offer numerous methods to measure body fat to the required degree of precision. However, there are no signs that inevitably characterize the condition other than the excess adiposity, which is the definition of obesity. The causes of obesity are numerous and diverse, ranging from and including combinations of environmental, behavioral and genetic aspects of energy intake, partitioning and expenditure. Its common accompaniments¾impaired glucose tolerance, dyslipidemia, hypertension¾are not inevitably present. Thus, condition (c) is met, but only in a circular or tautological sense: the only characteristic (pathonomic), identifiable sign of obesity is also the characteristic which defines obesity, ie fatness.

Condition (d) is even more problematic. The deviations specified range from simple deviation from normality, to impairment, interruption or cessation of vital functions. Moreover, what is meant by deviation from normality is not clear¾it can imply undesirable variation or simple statistical rarity.

Evidence for impaired physical and social functioning in severe obesity (eg BMI>40) clearly exists. In these cases, excess fat is usually accompanied by various signs of impairment and it can be argued that severe or extreme obesity would usually meet condition (d) for most definitions of disease, including those which specify impairment of function.

However, impairment is not inevitable or even usual in most persons who meet the present BMI or percentage fat criteria for obesity. In contrast to severe obesity, mild obesity only 'threatens' eventual impairment inasmuch as a risk factor, by definition, confers a greater probability of some future adverse event. Yet its association with these events is, at our present state of understanding, probabilistic. We cannot foretell who will develop an obesity-related health problem. In fact, some persons who meet the criteria for obesity will live long lives free of any of the morbidities known to be influenced by obesity. We are therefore placed in the conceptually awkward position of declaring a disease which, for some of its victims, entails no affliction.

Many obese persons are competent, functioning members of society. Nor do these persons necessarily subjectively consider themselves impaired, except perhaps insofar as they feel themselves victims of social discrimination. They might fail to meet some arbitrary standard of physical fitness (eg climbing stairs, running) but such a standard would also exceed the capability of many non-obese but sedentary individuals. While physical fitness is desirable, its absence has not generally been considered an impairment. It would be possible to set an arbitrary standard of fitness which many obese and non-obese people would fail to meet, and to consider this as evidence of impairment; however the present criteria for obesity do not do so.

A further conceptual problem arises when obesity occurs in a disease such as Cushing's Syndrome. Obesity is one of the components or signs of that syndrome. Is the obesity which is a sign of Cushing's disease, itself a separate disease?

In sum, to call obesity defined solely on the basis of a BMI or percentage body fat in excess of some threshold a disease leads immediately to the following problems:

  • the only sign or symptom may be the excess fat which is also the only defining feature of the condition¾there are no other inevitable clinical or subclinical signs;

  • many obese persons suffer no impairment as a consequence of their obesity;

  • it ignores the probabilistic nature of the relation between obesity and consequent adverse events which is accurately conveyed by the term risk factor;

  • it poses conceptual problems, eg is the obesity which is a sign of a disease, itself a disease?

They continue on, at great length about the various ethical issues involved - from the creation and fostering of a victim 'mentality' of the obese, to the issue of responsibilities that range from patient behaviors to obligation to provide medical treatment, from the problems of vested interests leading the cause to declare obesity a disease to determining who pays for treatments.

They come full circle and conclude, "None of the foregoing is meant to argue that obesity is not a public health problem of the first magnitude. However, it would be a mistake to attempt to label it a disease in the traditional sense in order to emphasize its importance if it does not meet reasonable criteria for such diseases. Conceptual clarity is a cardinal virtue in science and philosophy and it should not be sacrificed to expediency.

Finally, it seems neither logically necessary nor tactically essential to have obesity labeled a disease in order for it to be taken seriously. Public health measures and preventive medicine often receive generous funding (eg annual physical examinations, immunization programs, smoking cessation campaigns, promotion of exercise and active lifestyles). Whether and how our institutions and organizations pay for obesity treatment should ultimately depend on what health outcomes we value, how much we value them, and the cost of achieving them, not on whether obesity is labeled a disease."


  1. The 'war on obesity' already seems more like a war on fat people.

  2. Interesting. Using those rules a "runny nose" is just as much a disease as is obesity.

    Obesity is a symptom, not a disease.

    But if you want to go there, we must include super models and the overly thin as diseased too. This would include more than a few world class athletes as well.

  3. This is a complex topic, really. I mean, I think unless obesity is seen as medical and not behavioral, we're getting nowhere on a solution to it. But on the other hand if it's seen as medical, that implies some helplessness I think, since in today's society, disease is seen as something which falls on people out of the sky for no reason.

    Scurvy is a disease? It's caused and cured merely by eating?

    I'm not sure about the issue of 'fat storage' as a disease being complicated by the fact that the only visible 'sign' of the 'disease' is obvious excess stored fat. Maybe the real issue there is that the disease isn't the stored fat, the disease is the hormonal regulation system/function. Which is something you'd only see at a chemical or molecular level. The stored fat is the symptom of that chemical process.