Sam Heughan Caitriona Balfe
“Outlander” star Caitriona Balfe teased co-star Sam Heughan about his dedication to fitness. They are pictured at San Diego Comic-Con on July 21, 2017 in San Diego, California. Tommaso Boddi/Getty Images for IMDb

“Outlander” star Sam Heughan has to take care of himself in order to play Jamie Fraser, but it seems he is particularly good about sticking to his diet and exercise regimen. Co-star Caitriona Balfe joked about how “annoying” it is that Heughan always manages to stay in shape.

“He’s so good. It’s so annoying,” Balfe teased after MTV asked when Heughan last ate a doughnut and he couldn’t remember.

Heughan tried to claim he was naughty by eating a bowl of guacamole the night before, but Balfe pointed out that he shared his while she had one all to herself. The Scottish actor hadn’t even skipped the gym while attending San Diego Comic-Con.

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“That’s the thing. So we go to set, right? And you know, you get in at 5:30, 6 in the morning,” Balfe explained. “I’m like bleary eyed and [drinking] coffee the size of my head, and Sam’s like ‘Yeah, just been to the gym.’ And then he goes to the gym after work as well. It’s a tough person to be around sometimes.”

Balfe joked that she was waiting to find out when he cheats on his diet. “I really hope I find out he’s like a secret junk food, midnight eater,” she added.

Heughan recently discussed maintaining his diet in a Facebook Live interview with Roark Gym, where he was training while “Outlander” filmed part of Season 3 in South Africa. “Our schedule changes all the time,” Heughan said in June. “Last week, we were doing night shoots [for ‘Outlander’ Season 3]. We start at 2 or 3, pick up in the afternoon, and then we’re finishing at 4 or 5 in the morning. Yeah, it’s tough. And then you’re like, ‘When do I eat? When do I train?’”

“It’s about, I guess, adapting and not pushing yourself to a point where you’re stressed about it, but also fitting it in when you can,” the actor explained. “If you can’t fit in that hour and a half workout or that hour workout, why not go do 20 minutes? Or get up early and just go for a walk?”

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While it might be hard to imagine that a person can be that dedicated to a healthy diet, it’s pretty easy to believe after seeing Heughan’s new video for the South African edition of Men’s Health. He’ll be on the cover of the August issue, and he’ll soon be part of a series of workout videos on the magazine’s Facebook page. The teaser video shows Heughan working out shirtless.

“Outlander” fans will get to see more of Heughan when he returns to TV screens this fall. However, it might take a little while to see Jamie and Claire reunite after being separated for 20 years. “So the characters have their own lives and go through all the emotions of grief and acceptance of losing someone that they love. It would almost make a man faint,” Heughan teased at the drama’s San Diego Comic-Con panel (via TVLine).

“Outlander” Season 3 premieres Sunday, Sept. 10 at 8 p.m. EDT on Starz.