Drew Barrymore Drops 20 Lbs. — See the Before-and-After Pics!

Drew Barrymore has been working hard at the gym — and it's really paying off!

On Tuesday, Barrymore documented her weight-loss journey. Along with posting a series of photos, she credited her trainer Marnie Alton with helping her lose the weight.

Of their 15-year friendship, she wrote on Instagram, “This woman is my long time teacher and dear important friend. She has helped me. Healed me. Encouraged me to keep going when I felt like being strong was an insurmountable task."

"When I told her I wanted to transform my body for #SANTACLARITADIET she helped me," Drew added, referencing her Netflix show. "Every spring, when I would start training to become #SHEILAHAMMOND Marnie was the one who got me there. I lost 20 pounds and trained like a mother."

Stressing the importance of having a healthy mindset, the 44-year-old said, “We hope the people in the wellness world are actually healthy in their hearts and minds. It's not all about being terminators! It's about how to find yourself. How to be your best self. But we need guidance and we hope our teachers are smart and wise and sane! Marnie is one of the greats. Period. And if your [sic] looking for a life change or to find your consistent tribe, she is where I found mine."

Last year, Drew was “super honest” about life, telling “Extra” in Los Angeles, “It isn't easy every day, and some days are better than others. Some days you feel like you are on top of the world and killing it and some days you feel (like) 'I'm trying to find the will to live.' Some days are a mixed bag of both."