Cory Monteith has lost 20lbs thanks to his girlfriend.

The 'Glee' actor dropped the weight he gained earlier this year thanks to some encouraging words of advice from his co-star and girlfriend Lea Michele.

A source told In Touch magazine: ''When he brought Lea home to meet his family they were making fun of him in front of her. She's tell him she loves him no matter what but it was bothering him and he did something about it.

''She's vegan and eats organic and she totally changed his eating habits. He's exercising too. He loves the way he looks now.''

Cory recently cited cutting down on chocolate and more exercise as the key to his weight loss.

He explained: ''I'm doing CrossFit and I'm eating fewer Snickers bars.''

Cory also has a positive effect on Lea, and friends say they've noticed she is happier since she's been with him.

A source said: ''Cory is definitely having a positive effect on Lea. She's much less miserable these days.''