Anyway, while running 5 miles a day still, I immediately began gaining 15 pounds a month. Eventually I couldn't run anymore.
I'm sorry, but the argument from thermodynamics is as bankrupt at explaining fat gain as it is in explaining height gain for adolescents. For height gain, the fact that energy in equals energy out is a true statement, but the explanation is growth hormone. If you calorie limit a growing child, the child will be somewhat (not very though) stunted, but will make up the energy difference through lethargy and by consuming all sorts of internal tissues.
For obesity, the explanation is insulin. I cut carbohydrates almost completely from my diet in January. Otherwise I ate what I wanted when I wanted (I measure my consumption in pounds of red meat per day). I'm amazingly healthier. I've lost 50 pounds. I've gained so much muscle that I can do pull-ups. Fucking pull-ups at my weight. With low-calorie dieting, I couldn't do pull-ups until I had lost another 70 pounds past that point. I'm putting on muscle and losing fat, and I'm eating huge quantities at every meal. Plus I have a desk job and barely exercise.
The argument from thermodynamics assumes that the fat tissue is a trash can and that weight homeostasis doesn't exist. It's a bankrupt theory that can't explain diseases like progressive lipodystrophy (a disease which makes people obese and emaciated at the same time). It can't explain why people who starve the calories off are not the same at the end as normal thin people and almost inevitably gain the pounds back. It can't explain why 1950s treatment to get anorexics to gain weight was through injecting them with insulin and not feeding them any more than they had been (during treatment).
In summary, you're seeking a psychological explanation of a physiological problem. Kind of like the discredited quack Sigmund Freud often did, eh? A physiological explanation might lead to the suggestion that we eat the way we evolved to eat -- no refined carbohydrate.