Beyonce lost 65 pounds after giving birth to daughter Blue Ivy in 2012 and said she weighed 195 pounds at delivery.
Beyonce, 32, made the weight-loss revelations in part four of her self-titled documentary called "Liberation."
"I was 195 pounds when I gave birth," she said. "I lost 65 pounds. I worked crazily to get my body back."
The 5-foot-7 Beyonce, who now weighs a trim 130 pounds, said she wanted to show that becoming a mom doesn't mean losing your sex appeal. She said she wanted to inspire other moms, who often feel unattractive after childbirth.
"I wanted to show that you can have a child and you can work hard and you can get your body back," she said. "I know finding my sensuality, getting back into my body, being proud of growing up, it was important to me that I expressed that in my music because there are so many women that feel the same thing after they give birth."
Beyonce previously revealed that she maintains her weight loss by eating one vegan meal a day and working out rigorously several days a week, combining cardio exercise with strength-training.
Earlier this month, Beyonce and husband Jay-Z followed a vegan diet for 22 days (until Christmas Day), citing a desire for a "spiritual and physical" cleanse. It's unclear whether the superstar couple has stayed vegan.
Meanwhile, Beyonce said she wants to send the message to other new moms to not be ashamed of their sexuality.
"You can have your child and still have fun and still be sexy and still have dreams and still have yourself," she shared. "I don't at all have any shame in being sexual and I'm not embarrassed about it. I don't feel like I have to protect that side of me because I do believe that sexuality is a power that we all have."