Rafael Nadal blasted the current obsession with fad diets on Monday, especially the moves towards gluten-free eating popularised by Grand Slam rival Novak Djokovic.
Nadal, the world number two, insisted he has never been tempted to succumb to what he describes as a passing trend which will be replaced by something more fashionable in years to come.
"At the end of the day, all the small things can help if you don't get crazy. I always had the theory that the most important thing is be happy, enjoy what are you doing, and be fresh mentally," said Nadal.
"If have the gluten-free diet or have the perfect diet or these kind of things, which are supposed to change you or be a big sacrifice, but mean you are not happy the rest of the day, not being fresh mentally because that's a lot of effort for you, better don't do it.
"Not all the players who had success had the same diet or had the same style of play. Everybody's different.
"Now it seems like the gluten-free diet is great. After three years or four years we will find another thing that will be great, too. Then the gluten-free will not work anymore."
World number one Djokovic famously dropped pizza and pasta from his diet as he opted for gluten-free at the end of 2010.
The Serb then went on to lead his country to a first Davis Cup, claim three of the four majors in 2011 as well as rack up a 41-match winning streak.
On Monday, Venus Williams, playing in her 60th Grand Slam, said she too has adopted a vegan diet, a response to having suffered the fatigue-causing Sjogren's syndrome.
But the 33-year-old confessed to some lapses in dietary discipline.
"I used to love steak, so I do miss that," said the four-time US Open winner after making the second round with a straight-sets win over Belgian 12th seed Kirsten Flipkens.
"I'm a chea-gan -- I cheat a lot. You see a picture of me eating the wrong thing -- that's why I have already confessed."
Nadal, the 2010 US Open winner, started his 2013 campaign on Monday with a 6-4, 6-2, 6-2 breeze past American wildcard Ryan Harrison as he returned to New York after missing thr 2012 edition.
He spent seven months off tour with a knee injury before returning in February and going on to win nine titles and building up a 54-3 winning record.
Even in his darkest moments, the 27-year-old said he has never been tempted to tinker with his diet.
"All these kind of things that are news, I am not doing. I am happy with the normal diet. But I don't say it is negative. I will say everybody's free to do what he wants. Everybody are not working the same things," said Nadal.
"Nothing strange in my life. I practice. I go fishing. I play golf. I go party when I have the chance to go party. That's all. Really normal guy, normal life."