When you look at several diets associated with longevity, they turn out to all have some common features - namely "a diet high in fruit, vegetables, whole grains, nuts, and legumes."

Diet Patterns and Mortality: Common Threads and Consistent Results

https://academic.oup.com/jn/article/144/6/795/4589921

Legumes are also a common feature of Blue Zones populations - they were certainly not sick and fat. Rather the opposite - remaining slim and active during their extended healthspan