Is there any fat cell research that looks at ways to control fat cells?

I read that fat cells wink out and them replace themselves, and that at around 20 we have the number of fat cells we will have for the rest of our lives. So, I'm wondering if anybody is trying to discover a way to stop or reduce the number of fat cells that are replaced.

I also wonder if there is any research studying how to keep a shrunken fat cell in its shrunken state other than diet.

This also makes me wonder if the function of a fat cell is somehow connected to emotional states...causing the fat cell to store more energy after being triggered via a hormone released due to an emotion. Could then something such as teaching people to do the opposite where they learn to release endorphins or another (happy) chemical to keep their fat cells emotionally fed so that they are satisfied in their shrunken state.

Are their studies about depression and how it affects fat cells? Do fat cells of a happy person look different than a sad person?

Thank you Dr. Dean!