Surrounded by the harness racing elite, Mitch Marner vowed to eat like a champion horse this summer in his quest to muscle up for Mike Babcock’s Maple Leafs.

The coach has challenged the undersized first-round pick from 2015 to put on some pounds if he wants an edge in a training camp full of young prospects, many with a size advantage.

“Hearing those words out of his mouth makes you want to work harder and make that team,” Marner said Tuesday at Mohawk Raceway, where he was celebrity drawmaster for Saturday’s $1 million Pepsi North America Cup.

“He’s one of the first guys I talked to (at season’s end last month). He wanted to make sure I knew the summer was going to be hard, what I had to do and that buying into it was going to be difficult. But it’s going to be worth it in the end, if I do everything right.”

Skill-wise and in terms of production, there’s not much more the right winger can prove after winning just about every junior award in sight as his London Knights captured the Memorial Cup. But with just two options — make the Leafs as a full-timer or return to London — the 5-foot-11 Marner has vowed to go hard on the weights and the dinner plates like never before.

With 116 points in 57 games, Marner was the Ontario Hockey League’s most outstanding player and the CHL’s player of the year. Now it’s time to turn things over to MVC (most valuable chef), his mother Bonnie, who retired this summer to supervise his often questionable dietary choices.

“We’re liable to have some squabbles at the kitchen table,” Bonnie said with a laugh.

“He doesn’t like anything I want him to eat. He really like nachos with the cheese. He likes Skittles too, but I’m like ‘Don’t tell people that.’

“He does like peanut butter and jam sandwiches and steak and potatoes. He never ate potatoes before, now he realizes he needs to. I just want him to put the weight on and be healthy, with the right snacks, the protein shakes and the multi-vitamins.”

Both Mitch and Bonnie are counting on a late growth spurt such as older brother Christopher, who was about 5-foot-7 when he began high school, and is now 6-2 and close to 200 pounds.

“He’s got the same problem as me, he couldn’t get any muscle or food into his stomach,” Mitch said. “But the past two years he’s started to really put on the weight and hopefully it goes the same way for me.”

Bonnie says Mitch has already been guarding against late night junk food.

“I know his billets were feeding him well in the hockey season, but I’m back in the driver’s seat,” she said. “I can see that (he’s growing) a bit, he’s really focused on working out and eating the right things before he goes to bed. I made chicken with some rice and a glass of water last night.

“I think he’s taking it all seriously. We want to do what we can to make the Leafs. They also have a meal plan in place for him so he’s definitely in good hands.”

Marner only took about five days off after winning the Memorial Cup and went right into an exercise program at the Leafs’ practice facility where they have a small army of fitness specialists. Marner is there by 9 a.m. daily for training with a skate before or after. In the afternoons, his Mom takes control.

“She said she’ll be forcing food down my throat if I don’t eat it myself,” joked Mitch. “You want to get a quick start on the year. When you do that, you feel you’re ready for everything.”

LHornby@postmedia.com