Every single day about 40 percent of the genes controlling your metabolism go up and down in their activity according to your nutrition. When you are asleep, your body goes into a fasting mode since you are not eating while you are asleep. After you eat, specific pathways in your liver, muscles, fat, and pancreas turn on to turn your food into energy. You cannot change your genes which you inherit from the time of birth, but the actions of those genes are under your control. It is estimated that 80 percent of how you age is dependent on your diet and lifestyle. Identical twins raised in different environments can have very different body composition and health outcomes. Studies of identical twins where one is obese and the other is lean have also shown differences in the bacteria in their intestines called the microbiome despite having identical human genomes.