He's in pretty great shape for 90. I recently heard him give an interview and impressed how bright and quick he was, However he has seemed to put on a lot of weight more recently,...not good esp at his age. But as some drs say, they are not generally going to give someone 90 diet directions,
BTW he wonders if his health has been attributed to the fact that for decades he has been eating a hand full of blueberries (frozen or fresh) every day for decades. They have a antioxidant called pterostilbene, could that be a factor? It has also been shown another powerful antioxidant (and anti inflammatory ) called astaxanthan that has been shown in some studies that may be even more effective.
There are some lectures over on YOUTUBE on both compounds ,you might look into them just for general information,maybe even your or someone in your families health/well being...just make sure you listen to someone there with good credentials. You may find it an interesting area of physiology/pathology,.if nothing else..