Popular Science has more on the hormone from mouse livers that cuts sugar cravings:
The scientists found that in the rodents, a hormone generated by the liver suppresses the brain’s sugar cravings. The study was published last week in the journal Cell Metabolism.
Researchers have known for a long time that certain hormones affect appetite and cravings, but these hormones aren’t produced by the liver (they’re made by other organs). For this study, scientists decided to look at a liver-generated hormone called fibroblast growth factor 21 (FGF21), which they knew to regulate the energy level (carbohydrates) in the blood.
The scientists thought FGF21 might affect taste preferences, too. So to test the idea, they created two groups of genetically modified mice: ones whose bodies couldn’t produce FGF21, and another group of mice that would overproduce the hormone. Then the researchers offered the genetically modified mice different types of food with different levels of simple sugars, complex sugars, and carbohydrates, to see which type of diet they preferred. The mice without FGF21 had a strong preference for a high-sugar diet. Meanwhile, mice with overactive production of FGF21 went out of their way to avoid eating a diet of sweets.