Ramadan fasting turns the hunger hormone up, not down

Anyone who has fasted knows the practical question: does the body get used to it, or does hunger keep knocking? Appetite is steered by a set of hormones, including ghrelin, which signals hunger, leptin, which signals stored energy, and others such as insulin and gastrin. Ramadan intermittent fasting, a month of abstaining from food and drink during daylight, is a natural experiment in how a sustained fasting rhythm reshapes these signals. This review pooled the available studies in healthy people to find out which hormones actually move.

The authors searched six databases for research on appetite-regulating hormones during Ramadan intermittent fasting, published up to the end of March 2024. Sixteen studies qualified, covering 664 healthy participants, 51.4% of them male, with a mean age of 33.9 years. Hormone concentrations measured around the fasting month were pooled: 12 studies contributed complete leptin data, six contributed insulin, and three each contributed ghrelin and gastrin. Results were combined as standardised mean differences to allow comparison across studies.

Ghrelin, the hormone that stimulates hunger, rose significantly after Ramadan fasting, with a standardised mean difference of 0.31, and this finding was consistent across the studies that measured it. Leptin showed no significant change, though the leptin studies disagreed with each other considerably, which weakens confidence in that null result. Insulin showed no significant change either, and neither did gastrin. Of the hormones with enough data to pool, only ghrelin moved.

The result complicates the popular idea that the body simply adapts to fasting and hunger fades: at the hormonal level, the hunger signal was turned up rather than down after a month of daytime fasting. The evidence base is thin in places, with only three studies each for ghrelin and gastrin, and the inconsistency across leptin studies leaves that question open. The authors call for further research to clarify how this fasting pattern affects the full set of appetite hormones. How these hormonal shifts relate to what people actually eat, and to body weight, is not addressed here.

If a sustained fasting routine leaves you feeling hungrier rather than adapted, this is a reason to think that is your physiology talking, not a lack of discipline. The rise in ghrelin was measured in healthy adults observing Ramadan specifically, so other fasting schedules might behave differently. Nothing here suggests fasting is harmful; it simply shows the main hunger hormone climbs. It is information for setting expectations rather than a verdict on whether fasting is worth doing.