8 min read SIX MONTHS AGO , Men’s Health fitness advisor Bill Hartman, P.T., was like many of us: in decent enough shape, but heading in the wrong direction after years of eating on the go while working long hours. Sure, he exercised hard a few days a week and ate healthy foods.“But I didn’t pay attention to portion sizes,” he says. A snack of a handful of cashews, for example, often became five or six handfuls, leaving him with a 600-calorie tab. With the big 5-0 approaching, Hartman, a co-owner of IFAST Gym in Indianapolis, needed some inspiration. “Jack LaLanne would often do a big physical challenge on his birthday,” he says. “I thought maybe I should do something a little crazy too.” Hartman’s goal: to get shredded and regain the shape he was in back in his 20s, when he competed as a bodybuilder. He would need to muster more effort this time, because losing fat and building muscle becomes harder with every passing year. After age 35, diminishing testosterone and slowing metabolism add to the challenge.…