But generally (for adults anyway), it’s the amount of fat stored in each fat cell that’s changing, and the number of cells doesn’t vary much, if at all.

The Cell paper requires a paid account or one time payment.

Here are a couple articles reporting on the paper though:

https://www.the-scientist.com/news-opinion/epigenetic-manipulations-can-accelerate-or-reverse-aging-in-mice-70888

https://hms.harvard.edu/news/loss-epigenetic-information-can-drive-aging-restoration-can-reverse

https://www.news-medical.net/amp/news/20230115/The-loss-of-epigenetic-information-accelerates-the-aging-process.aspx