05/25/2012 at 08:00 AM EDT
As a former competitive swimmer and now a plus-sized model
, Kaela Humphries is used to having her professional life linked to her body.
Unfortunately, as an athlete in high school and college, her eating and exercising regimen was much different than it is now that she's stopped swimming.
"You are sort of used to living and eating a certain way, and then you are like, 'Oh my God, I can't eat 10 meals a day and 10,000 calories anymore,' " Humphries, 29, tells PEOPLE about having to alter her routine. "On top of that, I'm approaching 30 and it gets harder to lose weight the older you get."
of Kim Kardashian
's ex, Kris Humphries, Kaela says her post-swimming size fluctuated from size 10 or 12 when she was in high school to an 18 after college.
Humphries said she became motivated to lose weight so that she could fit into sample sizes in order to pursue a modeling career. Dropping 35 or 40 lbs. since late last year, she also lost 4 inches from her waist and is now a 14 or 16, she says.
"Looking healthy is important in anything you do," Humphries, who recently participated in her first photo shoot
for eloquii by The Limited, tells PEOPLE. "It should have been more of a priority earlier. But it's hard when you have a fulltime job in the real world and it's not your job to be in shape."
For more on Kaela Humphries's modeling career and exercise regimen, pick up the latest issue of PEOPLE, on stands now