If you ever need to gain 50 pounds, fast, maybe Chase Utley can hook you up.



It worked for Philly's Rob McElhenney, the creator and star of FXs "It's Always Sunny in Philadelphia," who, you've probably heard by now, pulled a DeNiro for the coming season, packing on the pounds to become "Fat Mac."



Though by the time you see him in the Season 7 premiere Sept. 15, McElhenney will likely be back to his fighting weight, or nearly so. (On Saturday, FX announced it had picked up two more seasons of "Sunny," making it the longest-running live-action comedy in basic cable history.)



When I ran into him at the raw bar at a Fox party at Gladstone's Friday night, the St. Joe's prep grad was already closing in on that goal. "I've lost about 25 pounds, almost 30 pounds," he said.



"I actually had a hard time gaining it," he said, consuming about 5,000 calories a day.



And just for the record, Mac didn't become Fat Mac by downing Big Macs, the way filmmaker Morgan Spurlock did for his documentary "Supersize Me."



"I tried to do it as healthy as possible. So Morgan ate McDonald's every day, three times a day, for 30 days. . . For me, it was more about volume. I wound up getting a nutritionist through Chase Utley" (who appeared as himself in "It's Always Sunny" last season).



"I told him that I was gaining this weight, and he said, 'Hey, I've got this nutritionist that I work with, who makes the meals for you, and he can do it in a healthy way.' So I called this guy up, and he's got this company that works with a lot of professional athletes, including offensive linemen. And offensive linemen have to gain as much weight as they possibly can.



"So I worked with him and said, 'How can I do this as healhty as possible?' So instead of just tacking on calories through Big Macs and crap, I tried to do it as healthy as possible. So if I had to eat a thousand calories, instead of a Big Mac, I would eat three chicken breasts, two cups of rice and a cup of vegetables. That got to be a lot after a while, but that was what I was trying to do," McElhenney said.



The payoff? A portly physique and a blood profile that didn't give his doctor fits.



"I went to a doctor for the entire run, and i was getting my blood drawn every few weeks, just to test my cholesterol, my liver, check for diabetes and my blood pressure. And everything checked out, all the way through," he said, adding that "we got to a point where my doctor said, 'As long as you're going to lose it, and not keep it on for a significant amount of time, then I should be OK."



So was it worth it?



"Oh, yeah. . . I looked enormous," he said, pulling out his phone to show me a picture (not, of course, before showing off a couple of shots of the photogenic Axel, his nearly 1-year-old son with wife and "Sunny" co-star Kaitlin Olson. "He's the best. Just the cutest kid").



How was Kaitlin about it?



"She was OK with it [particularly, Olson told reporters the next day, after she and the rest of the cast told McElhenney they wouldn't be joining him in this particular experiment]. Obviously, for a good two months I was severely overweight. For me, it wasn't about being fat was funny. That was never the intention. The intention literally stemmed from watching a few sitcoms, and I noticed that the actors were getting better looking as the seasons were going by, and. . . our show has always been about the opposite, about taking the glamor out of it and about deconstructing the sitcom, trying to make the characters as unlikeable as possible, and to me, also as unattractive as possible.



"So it was all about excess. It was about gaining the weight, but also about growing a disgusting beard and letting my hair grow, and it was greasy, and I was literally just trying to look as ugly as possible. Because I felt like I'd never seen that before. I'd never seen somebody specificially try to look as overweight and bloated and out of shape and unkempt and unruly as possible," he said.



And, no, he apparently never worried that, as our mothers used to say, his face might freeze that way.



"That was sort of to me one of the best parts of it. It was a complete and total willful lack of vanity. And living in Los Angeles, which is the mecca of vanity," that means something.



But though he tried not to let other people's perceptions affect him, he did notice a difference in attitudes, "certainly by the people who knew me and didn't know what I was doing. It was sort of like an elephant in the room, like nobody wanted to ask. It's not very polite to ask somebody, ''Hey, you gained weight?' So most of the time, people didn't say anything about it. They just looked."

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As for strangers, "What I decided was that I was going to turn off that gauge of, you know, thinking about my appearance. I just literally decided, I'm not going to worry about the way I look."



He found it "incredibly liberating, to just go oh, who cares. And I actually felt great. I felt great. And physically, I felt great. Which is bizarre."



Not so great that he wanted to stay heavy, though.



"To lose it, I dropped back down to 2,500 calories. And in about three weeks, I dropped about 15 pounds."



He wouldn't rule out another weight gain, though.



"I don't know. It turned out really well, so I might have to put it back on," he said.



So other than fat Mac, what can we expect from the new season?



"I honestly believe this: It's our best season that we've ever done," he said. "I'm really, really proud of this season. Our season premiere is going to be 'Frank's Pretty Woman,' in which Frank [Danny DeVito] starts dating a prostitute and so we decide that if she's going to be around, we should throw a 'Pretty Woman' her way and convert her the way Julia Roberts was converted, a la Richard Gere. Second episode, we go down the Jersey shore, which I'm really, really excited about."



They shot in Ocean City, but McElhenney stressed, it's not about Ocean City.



"The city of Ocean City was unbelievably welcoming and really helpful, from the police, to the lifeguards. All of the vendors on the boardwalk were absolutely amazing. I just don't want them to think it's about Ocean City. And we went out of our way. In some shots, you could see like various Ocean City signage and we went through and digitally -- which is expensive -- painted it out, because I was so sensitive to that. I wanted to make sure that no one thought we were talking" about the famously dry town.



"It's a family destination and it's a tourist-driven economy and we wanted to make sure that everyone knew we weren't disparaging Ocean City in any way."



Because that would be like having Snooki in Ocean City?



"Exactly."



"It was about taking the Jersey shore from the television show 'Jersey Shore,' and creating that environment."



The night before, I noted, MTV's "Jersey Shore" season premiere had drawn a record 8.8 million viewers.



"No, really?" McElhenney said, looking about as enthusiastic as most TV writers do when confronted with the popularity of supposedly unscripted TV.



"That's the world we live in. What're you going to do?"