The sweet release of biological stress markers

When you’re stressed, do you reach for the chocolate and ice cream? Up to 40%^[1] of people say they eat more during stressful periods, and that the foods selected tend to be^[2] high in fat and/or sugar. Everyone has a comfort food, but researchers are still working out the biological reason for why that is.

One possible contributing factor to why we prefer certain food is how that food affects our brain. The brain region of interest in this study is the limbic system. The limbic system^[3] is involved in processing emotions and some sensory input, as well as the formation of long term memories. Several regions of the limbic system respond to stress, particularly the amygdala and the hippocampus (the locations of which are shown in Figure 1). The amygdala^[4] is the region in the brain that deals with fear, aggression, and other emotional responses. The amygdala is the primary initiator of the hormone release that triggers our acute stress response, or our ‘fight or flight’ response. Men tend to have a larger amygdala than women. The hippocampus^[5] is one of the areas responsible for conversion of short term memories to long term memories. Under periods of stress, activity in the hippocampus^[6] is typically reduced.

Figure 1: The brain under stress

During periods of stress that trigger our fight or flight response, one of the many hormones released is cortisol^[7]. The main function of cortisol in this response is to generate energy from body stores (through breakdown of fatty acids and glycogen) for the muscle and brain. It’s previously been shown^[8] in animal studies that increased insulin levels (from ‘comfort food’ consumption) in the presence of stress-induced increases in cortisol levels creates a negative feedback loop that increases energy storage, reduces further secretion of cortisol, and decreases the stress activity in the brain. This study was designed to examine that specific feedback pathway in humans.

Regions of the brain’s limbic system are involved in controlling the body’s ‘fight or flight’ response to stress. Many hormones are released during this response, including cortisol. Eating comfort foods in response to stress may decrease the stress responses of the brain through a feedback loop that increases insulin and energy storage, and decreases cortisol.