PHOTOS Whitney Houston’s death inspired Mary J. Blige to get in shape

At 42 years old, Mary J. Blige proudly admits she’s in the best shape of her life. And the proof is on the December 2013 cover of Shape!

“My main exercise is cardio,” she told magazine of her fitness routine. “The treadmill is fine but running outdoors gives me the best results. I try to log 6 to 8 miles a week. I could be in the worst mood, but when I do my cardio I feel much, much better.”

As much as the goal of logging a certain number of miles per week helps Mary stay on track, she is primarily motivated by friend Whitney Houston’s tragic death.

“Whitney Houston’s death really crushed me. I saw someone so incredibly talented just diminish, and I refuse to go out like that,” Mary said of her fellow singer.

After Whitney’s death — which was officially ruled an overdose — Mary cut out alcohol.

“I haven’t had a drink in a year and three months. I had quit for a long time but started again about five years ago. I’m off it completely once more, and now I feel stronger than ever.”

Although she’s “exercised religiously” since the late 1990s, Mary revamped her fitness routine by learning to swim, which required her to overcome her fears. She also began to follow a gluten-free, dairy-free, low-carb diet, even though her primary goal is no longer weight loss.

“I hate being out of shape, but I don’t exercise just to lose weight,” said the nine-time Grammy-winner. “It makes me feel better when I get that run in. I could be in the worst mood, but when I do my cardio I feel much, much better.”