Dieting is notoriously difficult. Thanks in part to evolution, we love foods that are high in calories. Not only that, but once we have experienced the kind of high-calorie foods that surround us in the modern world, more nutritionally-balanced foods become much less attractive. But why?
To understand how the brain makes dieting so difficult, and high-calorie foods so tempting, the authors of a recent study turned to mice, where they could record and manipulate the activity of specific neurons involved in energy balance and reward. They asked how exposing mice to high-calorie foods affected their consumption of, and neural responses to, regular foods.
When researchers gave the mice access to both high-fat (HFD) and standard (SD) diets, mice completely stopped eating the SD almost immediately, and preferred the HFD. They then removed the HFD, and saw that mice still ate very little SD, and so lost substantial weight. This devaluation of regular food was so strong that even fasting mice presented with an SD ate very little — they would only eat a lot if the HFD was available. Just experiencing the HFD for 24 hours was enough time to make the SD less tasty.
To see how HFD exposure affects the brain’s response to food, the scientists recorded the activity of AgRP neurons, a population of neurons that is active during hunger and controls energy balance, and Source…