Everybody knows how hard it is, after one hits "a certain age", to keep one's weight under control. A happy marriage is another legendary prescription for adding poundage. I was commiserating about this sort of thing with a friend who, like me, carries around a few extra kilos ... and it occurred to me that a physical phenomenon (at least metaphorically) might cast light on the problem.

Envision a golf course, a terrain of gently rolling hills and dales. Life is good: a ball can roll and come to rest in the middle of the fairway, or if it gets sliced or hooked into the rough it's no big deal to knock it back on track. Eat a huge dinner and the weight comes off naturally, as you feel less hungry and eat a bit less for a few days. Miss a meal, and contrariwise catch up on the calories a little later.

But then there are sandtraps --- local minima that are devilish hard to get out of. These are metastable states, like the diamond form of crystallized carbon. Fall into one and there's a big barrier to overcome before you can get out again.

And unlike the gravitational potential on the surface of the earth, in the case of people there aren't just two parameters that control weight, there are myriads. Think of all the biochemical feedback loops in the body ... all the metabolic pathways ... all the psychological and physiological drivers that affect eating. This is a high-dimensional space, and the valleys don't stay in the same places either --- they move around over time. No surprise that few weight-loss methods work in the long run; everybody is different, changeably so.

(for musings on some tangentially-related themes see InStability (20 Aug 1999), StrangeAttractors (1 Sep 1999), and MultidimensionalMountaineering (13 Dec 1999)

TopicScience - 2002-03-27

(correlates: Metabo versus The Media, ByDesign, IslandsOfStability, ...)