All the more impressive, of course, considering how he had gained 60 pounds to shoot the new Vince Vaughn film Delivery Man.
His secret to shedding the the excess pounds?
"I cut beer out," the 34-year-old actor told Jay Leno during an appearance on Wednesday's Tonight Show. "I didn't drink for seven or eight months, which was really not that difficult for me."
However, Pratt admitted that it did impact more than just his weight.
"I'm not like a huge alcoholic or anything, but I always prided myself on being in a pretty good mood. And then I stopped drinking alcohol for 8 months and I realized from time to time I got grumpy. It's a nice social lubricant."
Pratt also talked about having to be away from his six-month-old son Jack while we was in London shooting Guardians of the Galaxy for five five months and the dramatic changes in development that take place at that age.
"Babies at six months old, they're like houseplants," he joked. "They're there, but they don't give much back. There's not a real reciprocal relationship. You put water on them, make sure the window's open and they're fine. But when I came back, [he was] this little blob of flesh, this little poop machine. He became this darling, precious personality, this little boy."
So what have father and son been doing since his return home?
"I taught him fart sounds lately," Pratt said. "[Wife Anna Faris] will be in charge of reading and things like that."
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