My cat is losing hair all over his body.he is a house cat.a bit over weight,he is on a low calorie food, was wondering what i can do

First, cats and dogs generally shed their coats in the spring and again in the fall. It takes a couple weeks to work it's way through the shedding phase, but this is just dead hair being replaced and is normal. Brushing or combing will not eliminate the shedding but will help keep the hair mess a bit more manageable and help to prevent hair mats from forming on the cat.

There are a few medical conditions that cause a general hair loss, but you need a real examination to tell if it is one of those.