People with low BMI aren’t more active, they are just less hungry and “run hotter”

A study published in Cell Metabolism found that individuals with very low BMI are less physically active and consume less food than those with normal BMI, challenging the idea that low BMI people have a naturally higher activity metabolism. Despite lower activity, these underweight individuals showed higher resting metabolic rates and elevated thyroid hormone levels. Their heart health markers remained good, suggesting body fat levels might be more influential than physical activity. The researchers plan to further investigate genetic factors and underlying mechanisms behind these findings.