Yes, John F Kennedy was healthy enough. He did not die from poor health, rather from an assassination. I personally have not heard of Kennedy's health issues if that is what this topic is implying. Even if he wouldn't have been fit for presidency, it's who would've been selected anyway, at the hands of the American People.
Yes, I agree that John F. Kennedy was healthy enough to serve as President of the United States. Although JFK wasn't the healthiest man alive, he was still fit enough to perform his presidential duties. He was diagnosed with Addison's disease but he was being treated for it, his health was being monitored.
How healthy is "healthy enough" to be President? The position requires a certain amount of health, certainly, since it's a high-stress round-the-clock job. But good health isn't necessary, if the individual has access to intelligence, wisdom and good advice. Many folks suffer pain from age-related diseases, such as arthritis or joint wear. Would that be a disqualifying amount of ill-health? Would diabetes? More people than ever suffer autoimmune diseases, suggesting that we'll have a president with rheumatoid arthritis or fibromyalgia in the next 20 to 30 years. I think we need to know if the President is unable to fulfill his duties. That would be "not healthy enough."
John F. Kennedy successfully and effectively served as president for four years, and was just beginning his second four year term. If his life had not been tragically cut short by a sniper in Dallas he would have done great things for the next four years, despite any health issues he had.