But the King City, Ont., native, who won Olympic gold in trampoline last summer in London, said her goal was to be the best at her sport — not to look the best in a gym suit.
"Comparisons (between girl's bodies) are something that start at a young age, and in our sport, our uniforms don't leave much to the imagination," MacLennan said Wednesday.
The 24-year-old who claimed Canada's lone gold last summer in London, is part of a Dove campaign — "Girls Unstoppable" — to help raise awareness about body issues among young female athletes.
Six out of 10 girls have quit sports because of how they felt about their looks, according to 2010 Dove research with girls ages 10 to 17.
MacLennan said she suffered from self-doubt when she saw that there were a lot of trampolinists who were smaller and skinnier. Her mom Jane was always there to help her see herself in a positive light.
"She said 'Ok, maybe you have thicker legs, or a bigger bubble butt' or whatever," MacLennan said. "But she'd say: 'How do you think you jump so high?'
"It's reframing it in a positive way and making me look at it like, OK, yes they might be smaller than you, but what's healthy for you? What's functional for you? What's going to help you achieve your real goals?"
MacLennan, who counts both her mom and fellow Canadian trampolinist Karen Cockburn as her mentors, reached her goal last summer when she flipped and twisted to gold in London. Cockburn, a three-time Olympic medallist, was fourth.
MacLennan has been busy ever since. She threw out the first ball at a Toronto Blue Jays game. She took the ceremonial kickoff at an Argonauts game.
"When I was practising I accidentally kicked the ball and hit somebody in the face," she said with a laugh. "It's interesting, it's a lot different from what I ever expected to be experiencing. But I've taken the attitude that I may as well give it a try while I have the chance and see what happens."
Compared to the gruelling months leading up to London, she's scaled back her training — but still trains six days a week. She's also working on her Masters degree in exercise science at the University of Toronto.
She knows there's the responsibility of being a role model that comes with being an Olympic champion, but said "That's definitely been one of my favourite parts about after London and being one of the older athletes is being able to chat with younger girls."
MacLennan, whose mom was a figure skater, said she was always encouraged to participate in sports.
"From the moment I was born basically, my mom had me in a Styrofoam bathing suit," she said. "As long as I can remember we've been a very active family, it's been a huge part of my life. I started trampoline at the age of seven, but I was still doing a number of different activities. Figure skating, swimming, ski racing, dance, sailing, golf. In school: volleyball, basketball, soccer — which I was never particularly good at.
"I guess they wanted us to get a taste of everything and then find what we loved and were passionate about."
MacLennan's first competition this season will be the Canada Cup in July in Calgary, followed by the World Games later that month in Colombia.
The world championships are in Bulgaria in November.
Cockburn, meanwhile, is four months pregnant. She and husband Mathieu Turgeon, a bronze medallist in trampoline at the 2000 Olympics, are expecting their first child.