At age 46, Jennifer Garner has been keeping herself in tip-top shape and it’s all because of her new beau, John Miller. The pair have apparently been going to the gym together and it’s been helping Jen get the body of her dreams!

“Jen’s in the best shape of her life and it’s wonderful that she’s got a guy who loves being physically active and is in super shape, too,” an insider recently revealed to Life & Style, going on to note that Jen’s new relationship is also a lot more different than her marriage to ex-husband Ben Affleck.

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“One of the big turn offs with Ben toward the end of the marriage was how inactive he was,” the source shared. “He let himself go and lacked motivation, but Jen and John are doing everything from pumping iron to Taekwondo to biking and hiking.”

Apparently the reason why Jen and John are “so hot together” is because “they’re both big body and health nuts,” the source added. But the Alias star isn’t the only one whose caught the fitness bug. Her ex-hubby recently admitted to trying Jennifer Lopez and Alex Rodriguez‘s 10-day, no carb and no sugar diet in an effort to be more healthy.

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“You know, I’d hate to be shallow about it, but I just did the A-Rod 10-Day Challenge, which I saw on this show and got inspired by,” he told Hoda Kotb on Today. “It was a little bit tough. But I did it, I feel better — it’s awful for the first couple of days because I am definitely someone who likes bread and sugar.”

Even though Ben admitted to cheating a little bit during the challenge, he said his new diet was still beneficial to him in the end. “There’s supposed to be no caffeine but I cheated a little bit I have to say,” he confessed. “It’s one of those things where it’s terrible but then you get through it and you’re like, ‘Oh, I feel pretty good.’”