Hate to diet? It's how you are wired

If you are finding it difficult to stick to a weight-loss diet, you may blame hunger sensitive cells in your brain, says a study. These specialised cells, known as AGRP neurons, are responsible for the unpleasant feeling of hunger that makes snacking irresistible, the study found.

"The negative emotions associated with hunger can make it hard to maintain a diet and lose weight, and these neurons help explain that struggle," said researcher Scott Sternson from Howard Hughes Medical Institute.

AGRP neurons, located in a regulatory area of the brain known as the hypothalamus, were clearly involved in feeding behaviour. When the body lacks energy AGRP neurons become active, and when AGRP neurons are active animals eat. AGRP neurons do not directly drive an animal to eat but rather teach an animal to respond to sensory cues that signal the presence of food.

"We suspect that these neurons are a very old motivational system to force an animal to satisfy its physiological needs. Part of the motivation for seeking food is to shut these neurons off," Sternson explained. The team also discovered a different set of neurons which generate unpleasant feelings of thirst.

Hunger affects nearly every cell in the body and several types of neurons are dedicated to making sure an animal eats when energy stores are low. But Sternson said that until now, what scientists had learned about those neurons had not completely matched up to something we already know: hunger is unpleasant.

"There was an early prediction that there would be neurons that make you feel bad when you were hungry or thirsty. This made sense from an intuitive point of view, but all of the neurons that had been looked at seemed to have the opposite effect," he said. In earlier studies, researchers found that neurons that promoted eating did so by increasing positive feelings associated with food. In other words, hunger makes food taste better.

(The findings were published in Nature)