The Manzanis actress, who recently revealed that her weight loss total has passed the 100lbs mark, admitted that she often felt lethargic when heavier and has never felt better since shedding the pounds.
"When I hit that mark, I went, 'That's it!' I have more energy than I've ever had in my whole life," Alley explained to People.
"My body had gotten really weak. There was nothing positive about being fat. I feel back to normal. I have my game again."
The 62-year-old has denied allegations that she is suffering from bulimia and threatened a lawsuit against those who started the rumours.
"Bulemmia, is a serious sitiation not to be taken lightly.. it can cause death..this accusation is degrading 2 those who from suffer it (sic)," she wrote on her Twitter page.
Alley is apparently in talks to pen a book about aging with publisher Simon & Schuster's Atria imprint, to reveal her strategies on how to look and feel young at 60.