Its a complicated process with a bunch of moving parts, but the main factor is likely lepetin which is a hormone that regulates fat burning. Extended periods of dieting lower lepetin. To increase lepetin, extended periods of carb-heavy eating do wonders, or just a general calorie increase helps too.
Think of it as an oil-change for your body. Get that bytch running again.
Dont get stupid on your diet though

. Stay on a defecit, just a bit less of a defecit.
You acually CAN overreat above maintenance for a little while and be OK, but beyond a day or two and you are risking fat gain