Casie Price, 43, 5' 4", from Marietta, Penn.
Before: 209 lb., size 20
After: 133 lb., size 2-4

Total pounds lost: 76
Total sizes lost: 9

Casie's wearing: C9 Champion: Cami Sports Bra ($20, target.com), Premium Seamless Tank ($10, target.com), and Performance Capri ($25, target.com)

For as far back as I could remember, I had been chubby. The trouble really began, though, after I gave birth to my son. At first, I lost the baby weight. But then I quickly piled it all back on, until I weighed more than I did while pregnant. It bothered me that I didn’t have the energy to keep up with my active son. My wake-up moment came when I found myself zipping into a size 20(!) bridesmaid dress for a friend’s wedding. It made me realize that the health concerns that run in my family, like heart disease and diabetes, could become a reality for me.

RELATED: The Baby-Weight Whisperer

Walk this way

I finally got serious in 2010, kicking off the year by resolving to reach my target weight through two strategies. The first: Walk two miles every day. The initial outings felt like an eternity—my legs ached so badly, and I could barely catch my breath—but once I made it part of my to-do list, I started shedding major pounds. The other: Clean up my diet. I opted for lean protein, such as salmon, and substituted heavy sides, like mashed potatoes, for a mixed-greens salad with balsamic vinegar and olive oil. In six months, I was down another 20 pounds.

Look who's running

When my progress stalled, I amped up my routine from walking two miles to eventually running six. By the following summer, I was at my lowest weight. To firm up, I incorporated strength training. This helped me get the killer body I had always wanted. Even better, I went from struggling to run a few miles to competing in half marathons. In the fall of 2014, I even placed first overall female in the Civilian Military Combine—a mud and obstacle course race that tests endurance and strength—at the age of 41. I felt more fabulous than ever!

RELATED: A Running Vacation Rebooted My Spirit

Casie's pound-cutting pointers

Easy, everyday tweaks like the ones below have helped Casie get and stay super fit. 

1. Bag it up: I portion out all my snacks, like almonds or sliced apples, ahead of time in ziplock bags. This lets me take my healthy eats anywhere while keeping my serving sizes in check.

2. Crush a quickie workout: On extra-busy days, I do a Tabata sequence—in just 20 minutes, I can get a full-body workout. It really revs up my heart rate.

3. Write it out: When I’m dreading the gym, I grab a pen and paper and map out my workout; having a game plan prevents me from wasting time or slacking off during my session.

4. Find sweet swaps: I love peanut butter. To avoid some of the fat that comes with it, I mix the powdered kind, PB2, into Greek yogurt. It gives me that nutty, creamy taste without the guilt.

As told to Lindsey Murray