Your brain has an altered response to desirable foods

Hungry? Well, let’s face it, that pizza looks much better than the salad. Don’t deny it salad lovers, we all know behind closed doors you look at plenty of food porn to satiate your desires. Understanding the motivations that drive us to eat is important when we talk about weight loss and how we attempt to structure diets. Now a new study shows that for overweight individuals, the brain responses differently to desirable foods., but hold that thought, because there is hope.

The study helps explain why people seem to find self-control to be so out of reach. It also shows how the diabetes and weight loss drug, liraglutide acts on brain receptors to make enticing foods seems less desirable. This is important for individuals who are high on motivation and low on self-control when they try to diet.

“We know that everything that controls our body weight and metabolism is integrated by the brain,” said senior author Christos S. Mantzoros, MD.

“This includes both internal stimuli such as hormones and stress, and external stimuli, such as the smell and appearance of enticing foods.”

The team used fMRI (functional magnetic resonance imaging) to study the differences in the brain activity of individuals who are overweight and individuals of normal weight when they are exposed to desirable foods. They also quantified the differences by using computer-based neurocognitive testing to observe alterations in the activity of specific brain areas.

Specifically, the researchers examined the glucagon-like peptide (GLP) hormone, which is secreted by the gastrointestinal tract to regulate metabolism. Glucagon is the evil twin to insulin; while insulin lowers blood sugar, glucagon helps raise it (which is needed and good). Evil because glucagon is a double edged sword, the release of glucose glucagon triggers is mostly in skeletal muscle tissues, which may or may not have health implications of its own. They also looked at the effect the GLP drug liraglutide on the brain activity of the subjects in the study.

They also looked at the effect the GLP drug liraglutide on the brain activity of the subjects in the study. The drug is already mainstream, it is used to help treat diabetes without the use of insulin, or rather it helps control blood sugar levels.

Liraglutide prolongs the action of GLP-1 receptors — which are just protein molecules that respond to the GLP hormone’s signal — and is known to work through the digestive tract and the pancreas. Previous animal studies had shown that GLP-1 may also act on the brain, but this had not been confirmed in humans, spoiler alert, it looks like that may no longer be true.

“Compared with animals, humans have a much more complicated central nervous system that regulates behaviors,” explained Mantzoros.

“Animals can teach us a lot about the hypothalamus and homeostatic system, which is responsible for feeding behaviors in times of starvation.”

“But human feeding behaviors also involve the brain’s cortical regions, in particular, the prefrontal areas responsible for cognitive control and decision-making. We wanted to find out if GLP-1 was acting on these brain regions in humans and, if so, specifically where and how.”

In a preliminary study, a team of pathologists analyzed 22 brain tissue samples for the presence of GLP-1. The findings confirmed their presence in several areas of the brain, including in the “reward” regions and, most importantly, in the cortical regions that are responsible for higher thought.

Next, researchers enrolled 21 study subjects – both men and women with diabetes – who were treated with liraglutide.

“We randomly selected half of the individuals to take liraglutide and the other half to take a placebo,” explained Mantzoros.

After a period of at least three weeks of receiving no medication, the subjects then “crossed over,” so that those who originally received the medication were given a placebo and those who originally took the placebo were administered liraglutide.

“This provided us the ability to see before-and-after results in the same individuals,” he explained.

Next, fMRI scans were taken when subjects were shown images of different foods, including both highly desirable cakes and fried foods and less desirable foods, such as vegetables.

The imaging results showed that liraglutide was decreasing activation in the brain’s cortex, the area that increases control and makes individuals more attentive to what they are eating. This result suggests that individuals on liraglutide find highly desirable foods less appealing — which is why activity went down and not up — and that the medication might prove an effective weight loss therapy for people who tend to eat foods as a reward, such as when they are stressed.

“Our findings open the possibility for combination drugs for the treatment of obesity,” said Mantzoros.

“This might create more powerful solutions and is something that remains to be explored. One-third of the U.S. population is obese and another one-third is overweight. This is a huge burden and increases the risk of diabetes, cardiovascular disease and many types of cancer. We need to continue to develop safe and effective therapies to combat this epidemic.”

Please note, no desserts were harmed in the writing of this post… or at least, there were no survivors to say otherwise. <insert evil laugh here> and just because they look tasty:

Sources:
Farr, O., Sofopoulos, M., Tsoukas, M., Dincer, F., Thakkar, B., Sahin-Efe, A., Filippaios, A., Bowers, J., Srnka, A., Gavrieli, A., Ko, B., Liakou, C., Kanyuch, N., Tseleni-Balafouta, S., & Mantzoros, C. (2016). GLP-1 receptors exist in the parietal cortex, hypothalamus and medulla of human brains and the GLP-1 analogue liraglutide alters brain activity related to highly desirable food cues in individuals with diabetes: a crossover, randomised, placebo-controlled Diabetologia DOI: 10.1007/s00125-016-3874-y