Well, you tried to help, but he's a grown person. He needs to live with his decisions. Just note, there's a huge difference between Keto and reducing carbs alone. I'm sure you're aware. I've done both, and Keto is a regime that is serious and should be done with care. My wife and I tried it and it put her in the hospital with a temporary liver condition. So, now we do the latter, which is just reduce carbs in general but not wipe them out entirely for protein and fats alone. It makes a difference (note what makes more of a difference is just cutting out the soda of any kind and drinking coffee instead).