Energy balance

A 25% caloric deficit induces mitochondrial biogenesis (increased mtDNA content and expression of biogenesis genes like PPARGC1A and SIRT1) in human skeletal muscle, leading to improved metabolic efficiency and reduced oxidative stress without increasing the activity of key mitochondrial enzymes.

If you are overweight but not obese, a sustained 25% reduction in calories for several months can reprogram your muscle cells to become more energy-efficient. This involves creating more mitochondria (the power plants of your cells) and upregulating specific genes (like SIRT1 and PGC-1alpha) that manage energy. Interestingly, this happens without necessarily increasing the speed at which your muscles burn fuel (enzyme activity), suggesting your body is becoming more 'efficient' rather than just 'faster'. This adaptation may help reduce oxidative stress and DNA damage associated with aging.