Body schema is hard to explain. It’s not how your body is qualitatively. That’s just a set of numbers (height in inches, weight in pounds, BMI, physical age, bone density, vision quality, how much you can lift, etc.). Body schema is the way your brain interprets those numbers and projects a subjective idea of how your body is in relative terms to other bodies or the way you think your body should be. And the relationship isn’t merely one of how I perceive my body now or later, but how I perceive my body changing and my feelings towards that change.

Roger Ebert, a man who has gone from a great movie reviewer to simply a great man, is going through changes. After cancer surgery took his jaw and his voice, Ebert has been blogging up a firestorm of self-reflexive observations and musings that give us a marvelous window into the way in which a razor-sharp mind views the deterioration of the biology which embodies it.

I am less of a person. Don’t talk to me about self-esteem. My self-esteem is just fine. I’m shorter, damn it all. In the last few years I’ve noticed a trend among the young woman who work as movie publicists in Chicago; many of them are quite tall. Now I am forced to wonder if this is because I am shorter. Yes, I must be, because I’ve been sitting in the same seat in the Lake Street screening room for at least 16 years, and only since my illness have I become aware of people’s heads sometimes blocking the subtitles. Is this because the younger movie critics are taller? Not entirely.

I saw a movie today titled “How to Live Forever.” It’s by Mark Wexler, who visits some old people, some very old people and various scientists and other experts on aging. He finds remarkable people. A Brit named Buster Martin is 101 years old and runs in a marathon, pausing for five rest breaks during which he has a pint of beer and a smoke. A former Disney animator named Tyrus Wong is 98 and builds and flies beautiful kites of astonishing complexity on the beach at Santa Monica.

Apparently aging is programmed into our cells. You’ve read the articles. If the aging process could be arrested, we’d theoretically live longer–assuming we stayed in good health. That’s a big assumption, since fast food is poisoning us with fats and sugars. Apparently long life depends on keeping active, staying interested, and eating a diet high in volume but low in calories, which means mostly grains and vegetables. So many of us, me included, know that in theory but don’t always follow it in practice. For a time I followed the Steak n Shake diet, which meant: Be a vegetarian except when at Steak n Shake.