I applaud the author's instincts: when you're not sure whether something really is an X, and hence deserves Y, the right thing to do is unpack the definition of X and ask what about it implies Y in the first place. In logic, definitions may have hard edges, but in real life the edges are fuzzy. Is a sham marriage really a marriage? It depends on why you want to know. The answer changes depending on whether you want to seduce the wife, settle a tax dispute, or research domestic social patterns.

The author stops short of really applying this approach. He rightly unpacks the definition of disease and observes that obesity only partially satisfies it. But he then discards the definition as useless and regresses all the way to first principles! You don't want to do that. That definition embeds some wisdom; there's got to be a reason we have it, after all. The next step is to ask which bits of the definition are relevant to the question at hand and see how well obesity satisfies those bits. The question he should be asking is not merely "What is a disease?" but rather "What is it about disease that warrants sympathy or treatment?"

The framing of deontology and consequentialism is particularly poor, and I find it unfair to the deontologist. (It is certainly quite silly to say the deontologist is trying to distinguish good from bad people. It's just a way of thinking about ethics, man, not a religion.) I would say that deontology says intentions matter and some actions are inherently bad, while consequentialism says results matter and some conditions are inherently bad. It is unfair to the deontologist to paint him as ignoring consequences; inasmuch as they can be known, they count as intentions. And it is unfair to the consequentialist to paint him as ignoring character; inasmuch as effects on character can be controlled, they count as results. Allow the two philosophies to account for all the known facts, and you'll find they give you very similar answers.

So, what's the difference between a disease and a character flaw? Why does the one warrant sympathy and the other warrant reproach? Why should the one be treated and the other conquered?

Asked that way, the answer is obvious. Diseases are unpleasant and involuntary -- simple misfortune. Treatment and sympathy are how you alleviate the misery, and there's no more to the story. But character flaws are more complex. They degenerate and run in packs. A sick person doesn't get new diseases, but a person with poor self control definitely accumulates problems. A person needs to conquer himself, conquer his problems, or he will lose his ability to do so. So our efforts are targeted at motivation. The misery of the situation is a mixed blessing: it sucks to experience, but it also teaches you consequences in a way you'll take seriously and motivates you to change. Quick and easy treatment can be counterproductive, and reproach can be useful to briefly raise the pain above the decision threshold--to shock the boiling frog so he jumps. (I say "can be" because people are always complicated...)

The distinction is critical. Treating a disease is the right thing to do, but treating a character flaw actually does damage. We need to avoid using a fire extinguisher on a flood or throwing an inflatable life raft on a house fire.

So is obesity more like a disease or more like a character flaw?

It depends on the case! It can be either or neither or both.

I know someone who is a very large woman--beautiful, self-confident, merry, old and full of life. "Eat right, exercise, die anyway," she might say. As an intentional choice, her obesity is not a character flaw. And it's certainly not a disease. She needs neither treatment nor motivation, sympathy nor reproach. The right reaction is to respect her right to make her own decisions, and not call it a problem if she doesn't think it is one.

I know someone who just had a baby and is carrying a lot of pregnancy weight. She is generally a motivated and disciplined person, and hates being so fat. She misses her old clothes and her old lifestyle. In this case, the obesity is most like a simple disease--unintended (if not exactly unforeseen), a simple misery. Sympathy is appropriate, and if there were an easy medical fix, it would do no harm.

Then again, look at that same woman a few months later. After a good stab at a diet, losing fifteen pounds, she succumbed to stress and sleep deprivation, abandoning the diet in an attempt to stay sane. Months passed. She built eating habits she didn't want, regained much of the weight she'd lost. Life improved, she started getting sleep, and she didn't go back on her diet. She became more used to her condition, though still unhappy about it, and the simple inertia of the circumstance left her with little motivation to change. What had originally become a simple disease was gradually becoming a character problem; she will need to ultimately address it or risk doing damage to her disciplined nature. Perhaps she still deserves sympathy, but a raised eyebrow when she goes for a second bowl of ice cream would probably do more good than harm. A quick medical fix might not help anymore (and might indeed do harm); she has habits that need to change, and only she can do that.

People are complex. That's the real moral here. Just as "disease" has a definition with fuzzy boundaries, obesity is not all the same. Understanding whether it is a disease means modeling the individual case and understanding the causes and effects and consequences.

Reality is almost always more complex than our definitions. The important thing is to learn to ask the right questions.