It was imperative that the critters shed their Christmas bulge as they were struggling to curl up into a ball to fend off predators.
Ramat Gan zoo is overseeing the hedgehogs' new eating plan after concerned members of the public brought them in.
Staff thought the creatures had probably been snacking on food left out for pets.
“A lot of people put cat food on the streets for the stray cats, which is very nice but ... the problem is that there’s other wildlife that eats it,” said zookeeper Becka Rifkin.
Sherman was one of the overweight mammals and weighed 1.6 kg, twice as much as a normal hedgehog his age.
He has since lost 120 grams after staff monitored his diet and left him to run around in an enclosure.
They hope the animals will be healthy enough to be released by summer.