"You have to strength train," Daniel Rosenthal, ISSA, personal trainer at Equinox, told POPSUGAR. "Think of strength training as your way of telling your body to preferentially burn body fat for fuel, keeping that precious lean muscle tissue and maintaining a high metabolism."
He went on to explain that if you only do cardio, the weight loss you experience will be both fat and lean muscle. "Decreasing your lean muscle will slow your metabolism and make further fat loss super difficult," he said.
Although he recommends strength training at least twice a week, Jillian Michaels urges women to strength train even more often at four days per week. Start with a couple times a week and work your way up until you find a routine that works for you. Here's an example of what a week's worth of strength training looks like.