Obese and Anorexic People Taste Food Differently, Study Shows

19 May 2016 --- New research has discovered that people with eating disorders have impaired taste sensitivities, compared to people at healthy weights.

Eating disorders that impact your weight — like anorexia nervosa, binge-eating disorder, or obesity — may also change the way you taste food, according to a new study out of the University of Colorado (CU) Anschutz Medical Campus.

The findings are published in International Journal of Eating Disorders. The CU researchers discovered that how your brain processes taste changes when you’re at an unhealthy weight, making it more difficult to differentiate between sugary water and regular water.

Taste may have a greater impact on our diets than first realized. Binge eaters or obese people tend to have brains wired like addicts for food, and they need to eat more in order to feel satiated or to fully experience taste in a pleasurable way.
People who suffer from anorexia, meanwhile, have been shown to have difficulty experiencing the pleasure associated with food. This makes them more likely to avoid enjoyable foods like burgers or ice cream, finding them repulsive rather than rewarding.

Both conditions are unhealthy and are caused by changes to hormones and neurons within the insular cortex or insula, a part of the brain that deals with emotion, perception, motor control, and self-awareness.

“Taste is an important driver of food intake and invariably associated with distinct neuronal patterns in the insula, the brain’s primary taste cortex,” said Dr Guido Frank, a psychiatrist and Associate Professor at the CU School of Medicine, in a press release. “If you can’t differentiate between tastes, that could impact how much you eat. That could also activate or not activate brain reward circuits.”

In the study, the researchers examined 106 women as they tasted both sugar water and a tasteless water solution. As the women were tasting the water, the researchers took brain scans to analyze the insula’s activity. They found that abnormal eating patterns — like anorexia or obesity —impaired the insula’s ability to identify taste. Participants with anorexia or obesity had a harder time telling the difference between the sugar water and the regular water, compared to control subjects — and even people who had recovered from anorexia.

The researchers aren’t entirely sure how the insula changes based on eating behaviors. They posit it may have something to do with changes in leptin, also known as the “satiety hormone,” which maintains energy balance by stopping hunger when necessary. Obese people tend to have a lower sensitivity to this hormone. Differences in taste could also be caused by structural changes, or impaired pathways, in the insula.

More research will need to be done in order to determine the exact mechanisms behind the association, but for now, the researchers hope that their results will provide some insight into treating eating disorders. For example, if people with anorexia are far more sensitive to taste in a way that makes food a negative experience for them, scientists could work on “adjusting flavor intensity by reducing it for those with anorexia and enhancing it for those who are obese,” Frank said. “It’s something we need to examine more closely.”