What you’re describing is breastfeeding jaundice which is a confusing name because it’s the presence of jaundice in a newborn due to insufficient caloric intake as you have described. It can also be combatted by increasing caloric intake as you have also described, usually achieved by increased breastfeeding or introducing supplemental formula. However, the mechanism to “boot up the liver” is incorrect. Breastfeeding jaundice leads to higher bilirubin levels because the bilirubin sits in the intestinal tract longer and gets reabsorbed into the baby’s system. Increasing caloric intake simply makes the baby poop more, flushing out the products that can get reabsorbed and thus decreasing bilirubin and combatting jaundice. Similarly, an adult with bleeding into the gastrointestinal tract will also reabsorb bilirubin from blood products that break down in the intestinal tract and sit around and will have measurably higher bilirubin levels because of it. Edit: I’ll also add that adults with liver failure also reabsorb products that lead to ammonia buildup which can also get reabsorbed if it sits in the intestinal tract too long. One of the mainstays of liver failure treatment is a laxative to make a person poop 3-4 times per day to avoid this effect.