This works for my wife's 92 year old dad. He goes from sunrise until mid afternoon. He keeps a very large garden. In the summer he keeps a two acre yard loaded with landscaping manicured. He must weedeat a half mile when he mows. He has hobbies. Before he sold a little bit larger spot of ground everything on the table he produced, meat and veggies. He sold the cows, so now veggies all year around. He's still going strong.

The only diet I've ever tried is a regular diet. (assuming light beer doesn't count)