Channing Tatumisn’t exactly known fornotbeing in shape, but he insists he feels like “a completely new person” in terms of his fitness these days.During a Wednesday appearance onThe Tonight Showto promote his first children’s book,The One and Only Sparkella,out now, the 41-year-old actor told hostJimmy Fallonthat his transformation during theCOVID-19 pandemicdidn’t come right away.“For the first week or two weeks, I definitely was just drinking beers and riding dirt bikes but I was like, ‘I can’t do this for two months. This is bad,’ " said Tatum.TheMagic Mikestar went on to say he and a friend “just went really, really hard” after that, in terms of “training every day.““And it was great — I mean,I came out a completely new person,” he said.Never miss a story — sign up forPEOPLE’s free daily newsletterto stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human-interest stories.Channing Tatum.NBC"How big did you get drinking beers and riding dirt bikes? Fallon, 46, asked his guest.“Pretty fat. I would say, you know, college 10 — a nice 10 lbs. And then I took it off,” Tatum said.The host then held up a black-and-white photo of Tatum that the actor hadpreviously shared on Instagramback in September: a shirtless selfie showing off his fit frame.“It’s like looking in a mirror,” Fallon joked.RELATED VIDEO: Shaun T Shares How Can Lose Your COVID-15 “Very Quickly”: “Just Try to Stay Consistent"Fallon went on to note that Tatum got in shape forhis upcoming movieDog, in which he is set to star and also make his directorial debut.As of December, he was also in final talks to appear alongsideSandra Bullockin the action-lacked romantic comedyThe Lost City of D.The latter film’s plot follows a romance novelist (Bullock, 56) who is dreading going on a book tour with the steamy cover model (Tatum) of her latest work. Things get much worse when a kidnapping attempt sweeps them both into an adventure, where the two eventually fall for each other under very dangerous circumstances.Ryan Reynoldswas previously attached to Tatum’s role. Back in October,Varietyreported that Reynolds, 44, might be reunited with Bullock for the action rom-com. (The two last starred together in the 2009 comedyThe Proposal.)

Channing Tatumisn’t exactly known fornotbeing in shape, but he insists he feels like “a completely new person” in terms of his fitness these days.

During a Wednesday appearance onThe Tonight Showto promote his first children’s book,The One and Only Sparkella,out now, the 41-year-old actor told hostJimmy Fallonthat his transformation during theCOVID-19 pandemicdidn’t come right away.

“For the first week or two weeks, I definitely was just drinking beers and riding dirt bikes but I was like, ‘I can’t do this for two months. This is bad,’ " said Tatum.

TheMagic Mikestar went on to say he and a friend “just went really, really hard” after that, in terms of “training every day.”

“And it was great — I mean,I came out a completely new person,” he said.

Never miss a story — sign up forPEOPLE’s free daily newsletterto stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human-interest stories.

Channing Tatum.NBC

Channing Tatum on Getting in Shape amid COVID Pandemic: ‘I Came Out a Completely New Person’

“How big did you get drinking beers and riding dirt bikes? Fallon, 46, asked his guest.

“Pretty fat. I would say, you know, college 10 — a nice 10 lbs. And then I took it off,” Tatum said.

The host then held up a black-and-white photo of Tatum that the actor hadpreviously shared on Instagramback in September: a shirtless selfie showing off his fit frame.

“It’s like looking in a mirror,” Fallon joked.

RELATED VIDEO: Shaun T Shares How Can Lose Your COVID-15 “Very Quickly”: “Just Try to Stay Consistent”

Fallon went on to note that Tatum got in shape forhis upcoming movieDog, in which he is set to star and also make his directorial debut.

As of December, he was also in final talks to appear alongsideSandra Bullockin the action-lacked romantic comedyThe Lost City of D.

The latter film’s plot follows a romance novelist (Bullock, 56) who is dreading going on a book tour with the steamy cover model (Tatum) of her latest work. Things get much worse when a kidnapping attempt sweeps them both into an adventure, where the two eventually fall for each other under very dangerous circumstances.

Ryan Reynoldswas previously attached to Tatum’s role. Back in October,Varietyreported that Reynolds, 44, might be reunited with Bullock for the action rom-com. (The two last starred together in the 2009 comedyThe Proposal.)

source: people.com