The answer, it seems, might not have anything to do with food at all. According to Shira Gabriel, an associate professor of psychology at SUNY, the key to understanding comfort food is that the "comfort" part of the equation is more rooted in social relationships and less in the fuzzy feeling of 20,000 new calories coursing through your veins.
In an experiment, Gabriel and a team of researchers asked volunteers to describe themselves in terms of how well they could form strong emotional relationships. If they could, they were classified as having a "secure attachment style." If they couldn't, they were classified as having an "insecure attachment style." The volunteers were then asked to describe a fight or conflict that they'd had with someone close to them ... at the same time as eating and rating the flavor of potato chips.
When the researchers reviewed the results, they noticed something interesting. The volunteers who'd described themselves as having a secure attachment style had, at the same time as describing their bust-up, rated their potato chips as tastier than those who rated themselves as having an insecure attachment style did. (They were the same chips, obviously.) In other words, the process of reliving the fight drove the "secure" people to seek comfort in the potato chips, whereas the "insecure" people didn't feel as much need to scarf them down.
This, along with similar results from other experiments, led Gabriel and her team to conclude that those "who have positive family relationships are more likely to reach for reminders of those relationships in times of sadness -- and often, those reminders come in the form of something edible." Gabriel compares it to classical conditioning. Which makes sense, considering that comfort food often triggers copious amounts of drooling.