Monteith dropped the weight he gained earlier this year thanks to some encouraging words of advice from Michele, reported Showbizspy.
"When he brought Lea home to meet his family they were making fun of him in front of her. She told him she loves him no matter what but it was bothering him and he did something about it," a source said.
"She is a vegan and eats organic and she totally changed his eating habits. He is exercising too. He loves the way he looks now," it added.
Monteith recently said that cutting down on chocolate and more exercise is the key to his weight loss.
"I am doing CrossFit and I am eating fewer Snickers bars," he said.