Let's talk about the American diet, for a moment. I don't mean, what Americans eat. I mean, what do most Americans mean when they "go on a diet?"

Almost always, they're saying that they're embarking on a new path for a short period of time, with the intention of going back to how things were as soon as possible.

In this case, sustainability isn't a question, it is part of the definition: I am going to do something that I have no intention of sustaining.

Although, it's fair to say that anyone with any sort of problem would want a sustainable solution, for some people, this will work. If they have a temporary problem — gained 5 pounds on vacation, for example — they don't need a permanent change. 

But if the problem is any larger or more enduring, why would anyone purposely, expressly, seek to solve it with a temporary, short-term change? It's planning to not solve the problem.

Another juncture of the two concepts came to mind last night as we watched a Cowboys-Vikings exhibition football game. (Dunno how that happened; I'm a big Patriots fan and can barely imagine watching a whole exhibition game involving them. But it got put on the TV, and then nobody turned it off.) At one point, the superfluous sideline reporter interviewed a 23-year-old fellow who is 6-foot-8 and 343 pounds.

I remarked how different his daily reality must be from mine, and my father-in-law, Clay, dissented: For one thing, he said, we both probably have to give more than average attention to maintaining our weight. My attention, of course, is focused on following a food plan that will keep me healthy while keeping me from my former food plan, which was to eat anything I wanted, in whatever quantity I wanted, at any time I wanted.

I expect the footballer, while probably having more latitude on choices, also needs a plan to ensure that he fuels his much larger frame and muscle mass, in a manner that supports his profession as a professional athlete. That can't be easy to sustain, just on whim.

Which brings me back to sustainability and obesity: People who are just plain huge, not for professional reasons but because of addiction, sloth, and anything in between, have a lot of sustaining to do: It requires more calories, obviously. But it requires more attention, too: What am I going to eat next? How am I going to get there? Where can I stop en route to my next appointment? How am I going to afford everything I want to eat?

Though very few obese people — as opposed to, say, professional athletes — would ever concede or admit it, you know that obese people have to work at sustaining such large body mass. That's certainly how it was for me.