The 63-year-old actress made the revelations while appearing on British late-night program The Graham Norton Show on Friday.
Appearing alongside co-star Arnold Schwarzenegger, Hamilton said, “I leaned out, worked for a year. Didn’t have carbohydrates for a year, then I show up on set and they were like ‘well, we have to build you a butt’ — which is interesting after a year of working out and leaning down they had to actually add a**.
“I would take pictures of my t**s and a** when I would get up in the morning and I’d get into my trailer and send it to my kids,” she added.
The star also revealed she ignored calls from the movie’s producer — and her ex-husband — James Cameron until he made it clear he wanted to discuss the work.
She told host Graham Norton: “We don’t talk at all. He rang three times and it was only on the third call when he mentioned it was about work that I rang him back!”
She added, “It took me a little while to decide if I had something more to do with her character.”
It is the first starring role Hamilton has had in a Terminator movie since 1991’s Terminator 2: Judgement Day. She first played the now iconic role of Sarah Connor in the 1984 movie The Terminator. The franchise was created by Cameron, who directed the first two films.
Sat alongside Hamilton, Schwarzenegger praised his co-star, saying: “Linda set the bar high for all female action roles. She really is a bad ass!”