It didn't cost her anything—in fact, she didn't even need to leave the house.

A good fitness routine doesn't always require you to sign up for a gym membership or attend pricey classes—in fact, research has shown you can actually walk to lose weight. And Jessica Slaughter, an 86-year-old woman who has dealt with obesity-related health issues for most of her life, is living proof that walking can help you shed serious pounds.

St. Louis-based NBC affiliate KSDK shared Slaughter's story and how she managed her weight loss journey earlier this week. Slaughter told reporters she has lost 120 pounds since changing her lifestyle after her doctor told her she was pre-diabetic in her mid 70s.

"Even as a kid in Mississippi, I was always the fattest kid in the class. I got teased a lot," Slaughter said. "I didn't know how to stop eating. Fried chicken. Bacon and eggs. Desserts, like cakes and pies."

The first change that Slaughter made was overhauling her diet. She adopted a vegan diet, eliminating all meat almost overnight—a weight loss tactic that some dietitians stand by. But the most effective lifestyle change she made was getting into a fitness routine which consisted of her walking around her one-bedroom apartment.

Slaughter didn't have to walk endless miles to see results, either. Slaughter simply walks in tight, short circles around her apartment; she tracks her daily steps using a Fitbit that was gifted to her by her granddaughter, and she says she walks 3,000 steps first thing in the morning.

"I walk 3,000 steps every morning before I start walking elsewhere," Slaughter says. "You don't have to go fast to get into shape; you just have to go. I want seniors to know just because we've reached a certain age, we don't have to stop living. There's a better way of life if they choose [it]."

More easy ways to increase daily exercise:

Brisk walking can be an effective form of exercise to help maintain weight, improve cardiovascular health, and ward off other chronic diseases such as type two-diabetes, according to experts at the Mayo Clinic. For seniors, it's also a great way to keep active while strengthening muscles in the body. The clinic says walking 30 minutes each day can help you maintain your health, but adults may see better weight loss results if they spend more than 1 hour walking throughout the day.

Slaughter's story is inspiring for many dieters, no matter their age. By sticking to a healthy diet and incorporating some form of exercise into your daily routine, you could see major results.