A rare genetic mutation affecting metabolism has been identified by researchers, potentially explaining why a small number of people maintain a naturally lean physique without intense calorie restriction. The mutation, found in approximately one in 7,000 individuals, involves the FNIP1 gene, which influences how the body converts food into energy.

In a study published in the journal Nature, scientists analyzed genetic data from over one million individuals across three continents to explore mutations linked to metabolic rate. The FNIP1 gene, which typically functions to slow calorie burning and promote energy storage during times of food abundance, was found to be "turned off" in people carrying this mutation. This inactivation causes the body to burn calories faster rather than store them.

“We evolved this gene to slow down calorie burning when food is plentiful, storing it to survive food scarcity down the road,” explained Dr. Luca Lotta, a senior author on the study. He noted that in today’s calorie-rich environment, this rare mutation, which may have been disadvantageous in the past, now provides an unexpected benefit.

Among roughly 150 individuals identified with one inactive copy of the FNIP1 gene, researchers observed lower body weight, reduced fat content—including liver fat—and increased lean muscle mass. These metabolic traits came with notable health advantages, such as lower cholesterol levels and a significantly decreased risk of cardiovascular diseases like heart attack and stroke, as well as kidney disease and non-alcoholic fatty liver disease.

To investigate the mutation’s effects more closely, the researchers conducted experiments with mice, selectively deactivating one copy of FNIP1. The modified mice exhibited resistance to weight gain and fat accumulation, suggesting potential therapeutic avenues for enhancing metabolism.

However, while the findings raise hopes for future drug development aimed at replicating these metabolic benefits in the broader population, the researchers emphasized caution. “Any therapy would be many years away,” Lotta said, acknowledging that gene reprogramming approaches have, so far, only been tested successfully in animal models, and their safety and efficacy in humans remain uncertain.

This discovery adds to the growing understanding of the genetic factors underlying metabolism and may eventually lead to novel treatments for obesity and related metabolic disorders, although significant further research is required before clinical applications become viable.