The US National Institutes of Health (NIH) has awarded a $2 million grant to study the effects of low-protein diets on metabolism. The four-year project, led by Dr. Chris Morrison, will investigate how reduced protein intake affects metabolism and food intake.
Dr. Morrison, a professor at Louisiana State University’s Pennington Biomedical Research Center, has previously researched how the brain detects changes in protein intake. His laboratory discovered that a hormone produced by the liver, fibroblast growth factor 21 (FGF21), plays a key role in signaling changes in nutritional status to the brain. The researcher’s earlier work showed that the hormone acts as a messenger linking peripheral nutrient signals with central neural circuits.
Understanding FGF21
FGF21 is a metabolic hormone that promotes metabolic health. It is increased by low-protein diets, which have been shown to improve metabolic health in animal models. Dr. Morrison explains that the hormone serves as a vital link between dietary protein intake, the brain, and metabolic adaptation. He adds that the rise in the hormone during protein restriction may trigger pathways that enhance insulin sensitivity and lipid metabolism.
The laboratory is now working to understand how this signaling system regulates changes in metabolism and feeding behavior during protein restriction. Morrison notes that more research is required before clinical or dietary recommendations can be made.
Protein and Metabolism
Previous research has demonstrated that dietary protein intake impacts metabolism and food cravings. The brain constantly monitors the body’s nutritional state and responds when protein intake is reduced. Dr. Morrison adds that animals detect when they are not eating sufficient protein and respond by changing both food intake and metabolism.
At the center of the study is FGF21, which rises in low-protein diets and appears to promote metabolic health. Morrison highlights that protein-restricted mice are hyperphagic, meaning they have increased food intake when their only option is the low-protein diet. When given a choice, these mice spontaneously prefer protein-containing foods and show increased motivation to obtain protein.
Research Goals
Dr. Morrison hopes to better understand whether high-protein diets offer any meaningful benefits for sedentary overweight individuals. He also wants to investigate whether reducing protein intake actually impacts functional performance and/or improves metabolic health.
As Dr. Morrison notes, there may be space for developing functional foods that try to tap into this mechanism, either using FGF21 as a biomarker or actively targeting protein or amino-acid restriction in an effort to drive FGF21.
