In professional sport, particularly boxing, the strain and changes on the human body are quite remarkable.
There have been some huge transformations right in front of our eyes with some of the beloved stars, and even some that have been more private.
One such boxer who fits into the latter category is Tyson Fury.
The Gypsy King was at the top of his game a number of years ago, but various issues, some more public than others, derailed both his physical and mental health.
He beat Wladimir Klitschko in 2015 and the struggles began after that.
The problems which he faced with addiction and depression saw him put on a lot of weight. He was originally private about it all, and now that he is hopefully back in a better place, and better shape, he became more open.
Someone like Fury being so open about his struggles with mental health is hugely significant and can have a positive impact on his fans. Love him or loathe him, the transformation both physically and mentally is profound.
Next, to his namesake Mike Tyson.
Just like Fury, he has also shed several stones on a recovery mission of his own.
Recently, in his older years, The Baddest Man on the Planet said he lost 100 pounds in preparation for his latest bout and weighed in at 220 pounds. The fight in question being the exhibition one against Roy Jones Jnr.
Tyson turned to a vegan diet after his weight ballooned to 27st. The demands of being an elite athlete would, of course, mean that after leaving the sport, it would be oh so difficult to maintain such an incredible physique.
Mike Tyson was able to do just that, though, and looked very healthy when he stepped through the ropes against Jones in Carson, California.