PID Diet

Being an electrical engineer, I was struck by the thought that one could look at weight loss as a simple controls problem with a single output variable (mass) and a single control variable, net calorie intake. (Actually, this is two control variables, gross calorie intake and calories burned, but they can be reduced to a single variable for the purposes of this model.) So why not apply everyone's favorite control scheme to dieting? I speak, of course, of Proportional-Integral-Derivative control, or PID for short. [See link for an explanation, if interested.]

With the accompanying book, you would receive a sort of calculator that would implement the PID algorithm. At the beginning of your diet you would enter your starting weight, the amount you'd like to lose, and some reasonable timeframe in which you'd like to lose it. The calculator would tune the P, I, and D gains accordingly. Each day you would enter your new weight, and the calculator would compute what your net caloric intake for that day should be based on the "error" in your weight (i.e., the difference between your current weight and goal weight).

But rather than simply telling you what your net caloric intake should be, the calculator would offer you a range of eating and exercising choices to meet that number. In the initial setup, you would enter the minimum amount of food you were willing to eat in a day, and the maximum amount of exercise you were willing to do. Each day the calculator would plot a line on this exercise-food continuum, and you would select any point on the line, knowing that they all would result in the proper net calorie intake for that day. When you select a point on the line, it could give you a sample menu and workout routine: at the low end of the line it might suggest eating 3 rice cakes and watching TV; at the other end it might suggest eating a whole pizza and running a marathon. Hopefully you'd choose a point closer to the middle.

I think people would go wild for a diet that was advertised as "using the same technology that keeps millions of factory robots working smoothly and accurately each day!" And who wouldn't have confidence in a diet that was designed by engineers, as we are generally regarded as paragons of physical fitness?