Snickers’s catchphrase, “you’re not you when you’re hungry” is now backed up by scientific evidence.

Researchers at the University of Guelph in Guelph, Ontario, induced rats with hyperglycemia and found that this caused symptoms of stress. The study, published in Psychopharmacology in October 2018, suggests that unfed animals are more likely to go through periods of stress and discomfort compared to those who are fed.

“We became interested in this topic because of the increasing interest in food addiction,” said Thomas Horman, a psychologist at the University of Guelph. “We thought it might lead to perpetuated addictive behaviors for sure.”

The researchers chose to induce hyperglycemia because it is a symptom of food deprivation. They followed a simple design where rats experienced normal conditions in one chamber and hyperglycemia in the other before giving the rats the choice to roam freely between the two chambers. Their time spent in the food deprived chamber was recorded, and many control factors, such as sluggish behavior and the presence of certain hormones, was controlled for.

The researchers concluded that the rat’s avoidance of the chamber that they experienced hypoglycemia in demonstrates that they most likely experienced fear, stress, or another uncomfortable symptom in the chamber, and that is why they spent less time there.

Previous research has shown that the hypothalamus, a part of the brain responsible for food and thirst cravings in humans, shuts off when blood glucose levels are low. This creates an imbalance in hormones that shuts off the serotonin receptors, which allow people to feel positive emotions, throughout the brain. The result is an increase in agitation, anger, and other similar symptoms.

Further implications of this study suggest that these ideas may translate to humans, and as a result, eating consistently and not allowing one’s body to enter a state of hyperglycemia may help with mood swings, and bouts of anger or sadness.
“Reading animal literature like rat studies is super important as it answers something that we would never be able to test in humans,” explains Jennifer MacCormack, a psychologist from the University of North Carolina at Chapel Hill. “The ultimate hope is that it will give us some clues that then we can develop some targeted studies in humans that then can test this.” It also explains the perpetual nature of diseases such as bulimia and anorexia, in which people’s lack of an adequate diet induces a sad, stressful, or anxious environment that causes them to not be hungry and continues the cycle.

In the future, the scientists plan to test whether hyperglycemia can have a long-term effect similar to depression.

“Now that we have established this is a stressor… looking at the effect this has as an incentive value and stimuli is one of the next steps we are going to explore and expanding on what we already know” said Thomas Horan. Results on this experiment may allow people to have alternative methods to help treat the symptoms of depression.