Modern Jane Fonda

Perhaps one of the driving reasons for fitness influencer success is that bodies are more enticing to look at, and that reigns true for females. In other words: sex sells.

"In the fitness industry, you're partly selling your body," Austin said. "I just followed Sierra Skye (@sierraskyee). I can be straight up with you — I followed her because I think she's really hot."

It's not an uncommon thought amongst influencers and followers. Hoebel believes that the difference in male and female anatomy is one of the many contributors to female influencer success.

"If you look at shirtless guy accounts versus a girl who's always in a bikini, I personally feel like the bikini accounts are likely to grow exponentially," Hoebel said. "The guy version of that — the shirtless guy — is not going to grow exponentially like that."

In most situations, half-naked bodies and sex work wonders for selling a product. But that's not the only reason why females are generating higher follower counts. Nicole Dunn, vice president of Dunn Pellier Media, represents both male and female fitness influencers through her company. Her experience in the industry echoes that of Mechler's thoughts — women relate to other women better over social media.

"Females talking about female issues would have a better rate at success than a male," Dunn said. "In my opinion, it depends on the brand and what they're putting out there."

The "brand" Dunn talks about is the workout. Working out for women typically isn't the same for men. It comes down to what muscle group each gender prioritizes. Kara Griffin knows this all too well.

Griffin (@feelthiswithkara), an up-and-coming fitness influencer in Los Angeles, trains people through two different workout styles. She practices her own brand called "Feel This" at Aura Yoga, which blends Pilates, dancing and yoga. Griffin is also an employee at Sweat Garage, where she trains clients through Sweat Garage's strength and weight workouts. While Griffin says both methods are for men and women, there's a disparity in who shows up for her "Feel This" classes.

"Typically, women will be drawn to the muscular endurance type workouts," Griffin said. "I do find more women in my classes. I do have men, but it's the minority for sure."

According to Griffin, men and women typically place emphasis on different muscle groups. Griffin's "Feel This" method works the whole body in what Griffin describes as a pyramid; a style of exercise that peaks in the middle with the highest intensity. The majority of the "Feel This" workouts are isolated in the glutes and core. On the other hand, her Sweat Garage workouts use heavier weights and are high intensity, and Griffin says she usually sees more men in those classes.

For Danielle Natoni (@daniellenatoni), another fitness influencer, men have never been part of her audience. Natoni says that 85 percent of her audience is women aged 25 to 45, and she doubts that'll change anytime soon.

"If I'm trying to be inclusive to males, and [I'm] talking about how hard it is to work out on my period — I'm not going to post that," Natoni said. "But it's relevant to my main audience."

Natoni's business model is to maximize her influence on females, and even compares her target audience to a doctor's specialty.

"There's general practitioners, but for the most part, most doctors specialize in something," Natoni said. "They know their niche, they know their market. When they do that, they're far more successful because they are focused and more direct."