Novak (along with Federer and Nadal) benefitted from the advancement in nutrition and conditioning since the turn of the 21st century. I wonder how long some of the 90s greats, like Sampras and Agassi, would have played if they had the nutrition and conditioning of today's players. I'm pretty sure Nadal would have been done by 30 if he had to play in the Sampras/Agassi era.
Novak cut out grains, carbs, people that cut out full grains, are usually Coelic's, to my knowledge Novak isnt a Coelic, he drinks a lot of protein shakes as athletes have to have a fair amount of protein in their diet, his diet is based on plant food? A lot of people followed the Coelic diet thinking they would lose weight? they did initially when people start eating their normal diet, the weight creeps back on. You have to have a balanced diet of carbs, low, and protein
Murray also followed this diet of cutting out full grains, carbs. Rafa has never followed that type of diet, he eats Nutella like it is going out of fashion and eats carbs with seafood. I cant speak for Federer, and his diet.
You body needs some type of carbs for fuel? to start with.
Personally I dont think that is an advancement in nutrition, from my medical point of view, though I know athletes drink a lot of protein shakes after their training and matches to refuel
I met Novak and his coach Marian Vjada at Rome 2013 and also at RG that year, Novak looked thin and thank goodness he has added some weight to his body, I will say Novak practices yoga and stretches daily one of the best things you can do for your conditioning especially when you get older