By 
Michael Phelps after gaining 25 pounds in 2009 (TVSmackTalk.com) and in top form in 2012 (Getty Images).
In addition to traveling the world and improving his golf game, Michael Phelps has one other goal for retirement.
He doesn't want to get fat.
"One of the things I want to do is I'm not going to let myself get out of shape like I did in 2009," Phelps said Sunday. "I gained like 25 pounds in six months. We're going to try not to go down that road this time around."
It might sound ridiculous that a world-class swimmer with a washboard stomach and negligible body fat is worried about putting on a few pounds, but Phelps did start to look more like an everyman than an athlete a few years ago. In the six months after he captured a record eight gold medals in Beijing, Phelps took a break from training, strayed from his diet and gained enough weight that one website ran a shirtless photo of him with the caption, "Where are the Abs?"
[ Related: Full video coverage of the 2012 Olympic Games ]
Phelps' 12,000-calories-a-day diet made headlines in the buildup to the Beijing Olympics, but he has since said that's a myth. Instead, he attributed his loss of muscle tone to a lack of incentive to train with the next Olympics so far away.
"I wasn't motivated. I did nothing, literally nothing, for a long time," Phelps told Details Magazine earlier this year. "I gained 25 pounds. A friend of mine and I were playing football on the beach in Miami, and somebody got a picture of us and put it all over the place. And he's like, 'Bro, you gotta start working out, man. You are fat.'
"I started going through the motions again. I would go back for a week or two and then stop. I'd show up for dry-land practice and then just sneak out the back door so nobody saw me. I was watching 'Rocky II' the other day — the one where he's fighting Apollo for the second time and he's just going through the motions. It reminded me of how I was."
What gave Phelps the motivation to begin training again in 2009 was that he wanted to make sure he reached his full potential in his sport. He won't have swimming to push himself to stay in shape in retirement, so he'll have to find another incentive.
[ Video: Australian TV snubs New Zealand ]
Some expect Phelps to pull a Brett Favre and come out of retirement in time for Rio 2016, but he's adamant that won't happen.
Fellow swimmer Dara Torres tweeted Sunday, "I'm betting @MichaelPhelps isn't done swimming....anyone care to wager???"
Responded Phelps, "Yes i would love 2!!!"
More Olympics coverage on Yahoo! Sports:
Related Olympics coverage on Yahoo! Sports:
• Video: Missy Franklin, "Everything was so unreal"
• Video: The legacy of Michael Phelps
• Video: One last medal for Phelps