Can Twitter make you fitter?

On a recent Saturday, Pat Wagner knew she should have been getting ready for boxing class.

The 60-year-old spent the past five years cutting her weight in half, dropping 150 pounds and adopting an entirely new lifestyle. She's no stranger to hard work or hard workouts, but on this day there were just too many distractions.

Errands to run. Laundry to do. A game on TV. She wondered — couldn't she take it easy?

Wagner began scrolling through her Twitter feed. She saw a post from her personal trainer, Steven Williams. He was in his own boxing class, and the post made Wagner decide to get up and get there, too.

"We all run up these excuses in our mind," Wagner said, "and we might know realistically that there shouldn't be an excuse, but it's amazing what the body can do and what the mind can make up."

Wagner is a living example of how social media can help you lose weight.

A quick scroll through Pinterest or a Google search for "motivation" shows that networking sites are brimming with weight-loss inspiration. But there's science behind the idea, too, according to a study published in the Journal of the American Medical Informatics Association.

It's also become a useful tool for trainers who want to motivate clients toward their goals, and clients who are looking for an extra push.

"The Twitter nudges do that," Wagner said. "They just reach out and say, 'Hey, get off your butt and go do this. I'm doing it; you need to do it.' "

Williams, Wagner's trainer, said he uses Twitter, Instagram and Facebook to keep his clients motivated during the crucial hours when they're working toward their goals outside the gym.

"It's almost like I'm with them throughout the day, as well," he said. "They always have a way to get hold of me, so it's almost like I'm with them 24/7."

Williams frequently sends out motivational quotes and reminders or posts pictures of a workout or healthy meal. It's a not-so-subtle message for clients who, like Wagner, might be lacking motivation.

His social media sites are also a means for his clients and other visitors to Gold's Gym in Uptown Dallas, where he works, to connect with one another. He's seen them share best practices and lean on one another through particularly tough workouts.

"It's just this endless cycle of mass information exchange," Williams said.

He said his own healthy habits make easy fodder for motivational posts. When he cooks a healthy meal that also looks delicious, he makes sure to snap a picture and post it for his followers; it's a little check that might help them adjust their own habits.

Gold's Gym general manager Edgar Valdez said the availability of social media has become a key, recommended component of the trainer-client relationship. It's almost like free marketing for individual trainers. He encourages both parties to follow each other on social media, and he's seen specific trainers amass a huge following.

"It keeps them engaged and gets them going to the next level, if you will," Valdez said.

Cassey Ho, founder of the website Blogilates, said social media help her followers feel as if they can connect with the California-based personal trainer.

"A lot of times they use that community as if they were like my clients, and so I'm really kind of like their personal trainer," Ho said.

Ho pointed to a recent partnership with the site DietBet, a social dieting game. Users agree to submit a set amount of money, weigh in and agree to a 4 percent weight-loss goal. Those who meet it at the end of the month split the pot. Ho's followers lost more than 31,000 pounds.

"To get the word out, Twitter and Instagram were really big," she said.

Each month, Ho releases a calendar with daily workouts. The calendars have their own hashtags, a symbol used to make topic searches easier on Twitter. A recent calendar featured the hashtag #thisisMYJULY, created by Ho to connect community members. She said this allows followers to ask about exercise modifications or answer one another's questions when she's not available.