© Keely Dellit At her heaviest, Keely Dellit weighed 278 pounds-so she decided to transform her diet by making one small change each day, and eventually lost 125 pounds in just 14 months.

As a kid, I was incredibly active-my parents were both athletes (my dad, a firefighter and surfer; my mom, a police officer and triathlete), so I simply followed their lifestyle: eating clean foods and playing sports.

Then puberty hit. Not only did I lose all interest in sports, but at 14 I got my first job working at a fast food restaurant-which meant all the free burgers and fries I could eat.

The weight piled on until my senior year, when I decided I wanted to lose it in time for my high school graduation. Through exercise and counting calories, I managed to drop 44 pounds. But once I moved out on my own after high school, I quickly regained all the weight I'd lost-plus a few extra pounds.

Over the next three years, I had three children-and any thought of losing weight went out the window. Honestly, I stopped weighing myself near the end of my last pregnancy because I just didn't want to know anymore.

My turning point happened the day I got home from the hospital after having my third child.

When I finally stepped on the scale-just days after giving birth-I weighed 278 pounds, my highest weight ever. I knew I had to make a change, not just because of the number, but because I felt unhealthy and exhausted. And because I wanted to get healthy for my three kids.

I wanted desperately to change, but I also knew that I didn't have the time to fully commit to a brand new lifestyle. So I had to find the easiest, kindest way possible to lose the weight.

I vowed to make one tiny change per week, which let me ease into a healthy lifestyle.

At first, I didn't cut out the fast food and treats that I loved; I simply chose smaller portions (like a small fry instead of a medium size). Then, I gradually made slightly healthier substitutions (grilled chicken instead of crispy, for example).

Once I got used to that, I swapped out soda for juice and then traded that for sparkling water. I cooked brown rice instead of white, tried plant-based milks instead of dairy, ate at home instead of ordering takeout. Those tiny, gradual changes allowed me to slowly transform my lifestyle.

Now, I follow a diet focused on whole, healthy, nutritious foods. Here's what a typical day of eating looks like (just FYI: I drink a lot of water, too-probably about one gallon a day):

Breakfast : two scrambled eggs and a small bowl of oatmeal with berries

: two scrambled eggs and a small bowl of oatmeal with berries Lunch : a large salad (lettuce, avocado, cucumber, carrots, peppers) with grilled chicken or tuna

: a large salad (lettuce, avocado, cucumber, carrots, peppers) with grilled chicken or tuna Dinner : steamed fish with a big pile of cooked veggies

: steamed fish with a big pile of cooked veggies Snack: protein bars, carrot sticks, or natural peanut butter.

I also started a workout regimen-but it definitely took some getting used to.

View this post on Instagram A post shared by Keely Dellit- Obese to PT (@losingkeelos) on Aug 6, 2018 at 2:54am PDT

For the first six months, I didn't follow a specific exercise plan-I just made it up on the fly: walking around the park with my children or following workouts I found on YouTube at home. But as I got stronger and more confident, I decided that it was time to step up my workouts, so I joined a bootcamp class.

I worked my way up to doing these bootcamp sessions every day (sometimes twice a day!). In fact, I loved it so much that I became a certified personal trainer so I could actually teach classes at the same gym.

In just 14 months, I lost 125 pounds-and now, my focus has shifted away from weight loss and on to building muscle and feeling strong.

I'm so happy that I made these changes, but it was definitely difficult at times.

You never realize how many celebrations revolve around food until you're trying to eat healthy. Sometimes I felt like I was missing out by saying no to things like cupcakes or pizza, and I still struggle with those feelings. Every day I have to decide to be mindful of my food choices and portion sizes.

But by losing weight, I also found my passion: health and fitness. Becoming a personal trainer has helped me share everything I've learned with others who are going through similar struggles. I learned that the trick to long-term weight management and health is to start slow and focus on all the little successes along the way-and now I want to pass that information on.