Fattening others

Don't gain too fast, and rub in body oils to keep the skin stretchy to help avoid stretch marks too. Lots of those oils are available for avoiding stretch marks during pregnancy but they work well for gainers too. It's hard to prevent them entirely though, this is all you can really do.

There may also be a genetic disposition to stretch marks. I have been gaining and I have totally avoided getting stretch marks. I have only gained around fifteen pounds, but I have rapidly gained several pounds in a matter of days. I'm quite old, so I do gain easily.