Studies of intermittent fasting have generally not shown any significant impacts on ghrelin, the gut hunger hormone. It’s normal to feel hungry while fasted, even after practicing intermittent fasting for several months. Drinking plenty of calorie-free fluids or eating up to 500 calories on a fast day can help manage your feelings of hunger while in a fasted state.
In studies of alternate day fasting, Dr. Krista Varady has tracked dietary restraint, hunger, fullness hormones including glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), and adipokines or cell signaling proteins secreted by adipose tissue including leptin. In clinical studies, IF has been found to decrease leptin, a hormone that helps control energy expenditure, and increase experiences of satiety after meals.