Why Does a Fat Graft Regenerate After Steroid Injections?

Fat cells do not regenerate. However, they can grow significantly in size with repeated weight gain even years after being transferred. You can undergo additional removal procedures as well. 

A fat graft does not regenerate after a steroid injection.
Sometimes, if the undesired fat graft consists of fibrous tissue, the steroid will be unable to melt the fat graft, and it persists.  If steroid injections fail, the graft can usually be removed with a small incision.

steroids can reduce swelling, cause atrophy of fat within the fat cell but does not change the number of viable cells. Fat grafts also have stem cells within it that can cause further expansion of the fat cells over time.

The injection of steroids into the skin is a significant event at the cellular level. After such an injection, your skin will be probably changed. The skin will be thinner and will have more difficulty healing. When a steroid is injected into a fat grafted area, the fat will shrink and contract. This may be the effect that he wants if steroid is injected into an area that may have a little too much volume.
 

Local steroid injections are used to address small pockets of fat .This fat will melt down and this should be done with care to avoid melting of the superficial fat which will result in skin discoloration.In general steroids will not make fat regenerate but over time the same area could have the accumulation of fat from remaining cells.