As well as feeding your pet the correct nutrition, promoting regular exercise will help the process of healthy weight loss.
There are some simple things you can do to help encourage your cat to be more active. For example, if it spends most of its time upstairs, bring it downstairs from time to time so that it has to make the journey back up to bed (and vice versa).
Here are some other tips you can try to encourage your cat to be more active.
Catch the light
Shine a white light torch on the walls and let your cat play (do not use a red light laser as it can damage your cat's eyes).
Playing with toys
Homemade or pet shop toys help to encourage your cat to get moving.
Try taking your cat out for a walk on a harness. Cat harnesses are available from your pet shop. While you're out, encourage your cat to jump and play using natural 'toys' like piles of leaves.