NIAGARA FALLS, Ont. — Zapping sugar was the worst part.



For Josh Leivo, becoming a caveman this past summer meant giving up any and all things sweet. No more treats after dinner. No Gatorade after workouts. No pop. No juice. But it was more than that. Adapting to the paleo diet meant more or less mocking the eating habits of a caveman with “just meat and veg” as Leivo described it after the first day of on-ice workouts at Leafs training camp.



“It’s a cool diet, but it’s hard to do with hockey,” Leivo said.



Of increasing his commitment to nutrition and sleeping habits during the offseason after another fruitless NHL season, Leivo added: “I just took it a little more serious, I guess, in the summer, just put my mind to it. I know this is a big year for me.”



If it feels a little like deja vu it’s because Leivo, now 25 and far from a prospect, has been in this exact same predicament for...