Why Unexplained Weight Gain Occurs: An Alternative Hypothesis
Unexplained weight gain frustrates millions of Americans who work vigorously to count calories and stay physically active. In fact, weight changes (both weight gain and loss) seem to occur in conjunction with a wide array of non-diet-and-exercise-related factors, such as medication therapies, hormonal changes, injuries to the brain, diseases, and even insomnia and stress.
The boilerplate explanation for unexplained weight change is that somehow the people who gain weight must secretly be taking in "extra" calories; and the people who lose weight must somehow be burning off "too many" calories.
The Lipophilia Hypothesis disagrees. It says changes at the level of the fat tissue itself drive changes in appetite and activity. So maybe what's happening in many cases of unexplained weight change is that the drug/disease/etc changes concentrations of insulin, LPL, blood sugar and so forth. These changes then affect changes in the fat tissue which then drives the body to establish a positive or negative caloric balance in order that it can "maintain its stock" at the new equilibrium.
This is a radical proposition. But at least it's testable. The Caloric Balance Hypothesis, on the other hand, tells us absolutely nothing about what might cause this phenomenon.