If you follow the NBA during the off-season, you may have noticed LeBron James sporting a leaner physique. The 29-year-old forward for the Cleveland Cavaliers recently revealed during the unveiling of his new "LeBron 12" signature Nike sneakers that the summer diet was a serious test of mental fortitude. 

"I had no sugars, no dairy, I had no carbs," he shared. "All I ate was meat, fish, veggies and fruit. That's it. For 67 straight days."

While James' gave no final tally of his weight loss, saying only that it was "a ton," ESPN's Brian Windhorst earlier speculated that the four-time MVP had dropped 10 or 12 pounds during the off-season. While James told Oregonlive that the diet offered a great mental challenge, Windhorst says the star was also likely looking to regain a physical advantage out on the court. 

"LeBron was probably, coming off his wedding and everything, he was probably in quote-unquote 'the worst shape he's been in a while.' He was obviously fine, but he got off to a slow start last season," he told Grantland.

As for the diet itself, it's clear that cutting out sugar, dairy, and carbs can have a dramatic effect on a person's physical energy and look. Back in 2012, actor Alec Baldwin took a similar path, cutting out artificial sugars completely and losing 35 pounds over four months. 

"I've eaten sugar in some fruit. I just try and eat berries," he told USA Today. "Candy, gum, mints, ice cream, cake, pie, that's all gone."

We'll see how well LeBron James' new form translates to the basketball court after the regular season begins on Oct. 28. 

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Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

The healthy clean diet LeBron James used to get lean
NBA star says he lost more than 10 pounds over the summer in an effort to get fit and 'test his mental fortitude'.