To my understanding, the logic is that there's a hormone called leptin which strongly guides your eating patterns, cravings, energy, etc. Stresses and traumas can affect your leptin levels, so particular stresses and traumas can cause you to eat more. This makes evolutionary sense, since if you're in a famine, or an ice age, you better stock up on as much food as you can. Move slowly, digest slowly, don't lose any of it, because you never know when you'll run out.
Sexual abuse traumas get interpreted by some bodies as the same kinds of stress signals as famine, raising leptin, causing overeating.
So I guess the broader point is that some of the "unconscious logic" going on inside us isn't just habits or odd personality traits, but actual chemical processes.
Note that I got all of this knowledge from reading a Pop Sci weight loss book. HN, let me know if you know better :-)