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Arya Sharma

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Is Obesity a disease?

Last year, the American Medical Association officially acknowledged obesity as a "disease." Not everyone agrees. There is no doubt that excess weight can cause a wide range of health problems, including heart disease and cancer – not unlike smoking. But, while we may consider smoking an addiction, we would hardly consider it a disease. So why should obesity qualify?

There are at least three reasons why obesity is different.

The first is related to the complexity of energy balance. While simplistic notions of balancing "calories in and calories out" work well in physics, with obesity we are dealing with physiology (which I like to describe as "biology messing with physics"). Our bodies do a remarkable job of sensing changes in caloric intake or expenditure and show a wide variation in how they respond to such changes.

Overfeeding studies at the Mayo Clinic showed an almost four-fold difference in the amount of weight gained by healthy volunteers who were all fed an extra 1000 calories per day for eight weeks. Similarly, numerous studies have shown that individuals following exactly the same diet or exercise program will vary widely in their weight-loss response.

No amount of binge eating will turn Jack Sprat into a sumo wrestler. Meantime, his wife may well find herself stuck with her own excess weight, no matter how hard she tries to lose it.

Which brings me to the second point: Once established, obesity becomes a chronic problem. This has to do with the fact that our bodies will always defend the highest weight that we have achieved. We refer to this as the "set-point." No matter how you got to 200 pounds, once there, it becomes the weight that your physiology will defend (and it will do so most effectively).

We not only have increasingly better insight into exactly how this set-point readjusts to ever-increasing body weight (through a process of inflammation and micro-scarring in the hypothalamus, the brain centre that regulates energy balance) but we also understand many of the hormonal and metabolic changes that occur as our bodies effectively defend their increasing fat mass.

Rather than viewing fat tissue as a simple storage depot for excess calories, we now look at body fat as a complex organ that interacts closely with other organs to maximize and sustain fat stores (perhaps in preparation for the next famine, even if it never comes).

This complicated physiology, and not simply a lack of motivation or willpower, is the real cause of yo-yo dieting. Indeed, the few people who do succeed in losing weight and keeping it off, will have to continue fighting their obesity every day (whether through caloric restriction or considerable amounts of exercise). For the rest of their lives, they will continue to be at risk of regaining weight should they ever abandon or even slightly reduce their efforts.

Thus, once established, obesity itself creates a vicious cycle that "locks in" a higher body weight. This altered physiology explains why telling someone with obesity to simply eat less and move more to treat their obesity is about as effective as telling someone with depression to simply cheer up.

The third reason that warrants considering obesity a disease is about access to treatments in our health care system. While we spend billions of dollars each year treating the consequences of obesity, we spend almost nothing on preventing and treating obesity itself. Whether we consider access to behavioural, medical or surgical programs for obesity, these are virtually non-existent in our health care system. Compare this to the wide range of specialized services routinely offered to patients with diabetes, heart disease or any other chronic condition (funny enough, – even smoking).

Unfortunately, obesity continues to be viewed by governments, payers, healthcare professionals, media and the public as being largely caused by laziness and over-consumption, a stigmatizing oversimplification of a complex health problem.

In contrast, if governments, healthcare professionals, health benefits payers, media and more individuals viewed obesity as a disease, we can perhaps create a world where health professionals are trained and remunerated for providing treatment services, where people with obesity can seek medical assistance with confidence, and where funders see the provision of obesity prevention and treatment resources and related research as a priority.

Arya M. Sharma is Professor and Chair in Obesity Research and Management at the University of Alberta. In 2005, he spearheaded the launch of the Canadian Obesity Network. He is also Past-President of the Canadian Association of Bariatric Physicians and Surgeons. Dr. Sharma maintains a widely-read blog on obesity prevention and management. You can follow him on Twitter @DrSharma