I think it depends on the person.. When I'm unhappy, I tend to not eat as much. When I do, I splurge on a few pieces of chocolate/that's it. I think habitually, as a kid, I always ate healthy.. so when feeling like crap, overeating/eating unhealthy just makes me want to gag.
Growing up, there was a saying in my house, "Not eating much huh? In love?" Even when people are in love, they also tend not to eat as much.
Either way, the only time in which I do eat a bit more than usual is when I'm studying my ass off/the weather's cold outside (this part biologically makes sense- since body fat storage is needed as a blanket for cold weather protection).