Energy balance

Feeding rats a cafeteria diet with low protein content (approx 7%) significantly increases energy expenditure and brown adipose tissue (BAT) activity compared to normal or high protein cafeteria diets, primarily through sympathetic activation of non-shivering thermogenesis.

This research suggests that when consuming highly palatable, energy-dense foods, a very low protein intake might trigger a specific metabolic defense mechanism (increased brown fat activity) that burns off excess calories. However, this comes at the cost of stunted growth and reduced fat-free mass in rats. For humans, this highlights that diet composition (specifically protein levels) significantly influences how the body handles excess energy, but it does not recommend low protein diets for general use due to the negative impact on lean mass.