For women, strong is the new skinny

When Katy Brinkley began going regularly to World Gym in Fairfax, Virginia a few years ago, the last thing on her mind was picking up dumbbells. "I just wanted to lose weight, get skinny. I was absolutely miserable where I was," she told CBS News. "I had that 'stuck' feeling and needed to make a change."

However, cardio exercise -- such as running on a treadmill or using a stationary bike -- wasn't cutting it. So she picked up some weights and everything changed. The teacher and single mom recently lifted more than 215 pounds, more weight than ever before.

Society's idea of beauty and health constantly changes, especially when it comes to women. For decades women have spent hours at the gym in an effort to achieve a slender -- even skinny -- physique.

But lately this appears to be changing. Men have been pumping iron for decades, and now it seems more women also want muscle-bound bods. They're incorporating strength training into their workouts and focusing on toning rather than getting skinny.

More gyms are jumping on the trend and offering classes that emphasize building muscle over burning calories. Aerobics and Zumba are giving way to kettlebells, Crossfit and P90X.

Vida Fitness in Washington, D.C. markets the concept with their slogan, "Strong is the new skinny."

"I would define it as a movement -- it's a positive movement for the fitness industry," Chandini Hemrajani, a trainer at Vida Fitness, told CBS News.

Anthony Tran, the fitness director at World Gym, said this trajectory is common for women who visit the gym. "I tell them they gotta lift weights! And you gotta lift heavy weights," he told CBS News.

Experts say weight-bearing exercise helps women's bodies recover faster, staves off osteoporosis, boost their immune system and improve balance. It also helps fast-track weight loss.

Brinkley has shed 30 pounds since she picked up weights, and she's found the more weight she lifts, the more she loses.

"I feel so much better, and I have a ton of energy, " she said.