They might, however, contain it and stop the deaths of many of the young, vigorous people whom poor countries need.

ECONOMIST: Even in Africa, it can be won

For "lean" and "fit" you could easily transpose "young" or "vigorous".

BBC: Analysis

In choosing a 76-year-old pope, the cardinals clearly decided that they didn't need a vigorous, young pope who would reign for decades but rather a seasoned, popular and humble pastor who would draw followers to the faith and help rebuild a church stained by scandal.

NPR: Argentine Jorge Bergoglio Elected Pope Francis