How much do hunger hormones change during contest prep?

Short answer

A lot. In 7 people over 10 weeks of prep, the hunger hormone rose 20.4% and the fullness hormone fell 27.7%. After the contest, 3 to 4 months of eating more brought the fullness hormone back to where it started.

How much do hunger hormones change during contest prep?
'Leaner → hungrier, less full' — but by how much?
Getting very hungry near the end of contest prep is a common experience. The body has a hormone that signals hunger (ghrelin) and one that signals fullness (leptin). We looked at studies that measured both in people preparing for a contest.
The hunger hormone went up
Up 20.4% by 5 weeks out
7 people were tested 11 weeks, 5 weeks and 3 days before a contest. As they lost 4.1 kg of body fat and reached 6.5% body fat, ghrelin rose 20.4% by 5 weeks out. It rose another 6% by 3 days out, but that change was not clear-cut.
The fullness hormone went down
Leptin fell 27.7%; people not prepping stayed the same
In the same 7 people, leptin fell 27.7% by 5 weeks out and did not drop further after that. 7 people who trained but did not prepare for a contest showed no change over the same period. The hunger signal got louder and the fullness signal got quieter.
Longer prep, bigger change
In 1 person who prepped for 8 months, ghrelin about 2.1 times higher
In a case of 1 person preparing for 8 months, daily intake dropped from 3,860 kcal to 1,724 kcal and body weight fell 9.1 kg. Ghrelin went from 383 to 822, about 2.1 times higher. That was a much bigger change than the 20.4% in the 10-week study.
What about more people?
In 23 people, leptin fell in both men and women
In a study of 23 people preparing for 23 weeks, leptin fell in both men and women. Women, who started with higher leptin, saw a bigger drop. Daily resting calorie burn, adjusted for body size, also went down.
Does it come back after the contest?
3 to 4 months of eating more brought leptin back
27 women who cut 35-50% of their body fat over a 4-month diet saw a big drop in leptin. After the contest, eating more and doing less cardio for 3 to 4 months brought leptin back to the starting level. In the 23-person study, too, levels moved back toward baseline after recovery.
Summary: the hunger signal grew and the fullness signal shrank
Ghrelin up about 20%, leptin down about 28%, then recovery
Over 10 weeks of prep, the hunger hormone rose 20.4% and the fullness hormone fell 27.7%. In 1 person who prepped for 8 months, ghrelin was about 2.1 times higher. In the 27-person study, eating enough for 3 to 4 months after the contest brought leptin back.