Gwen Stefani is trying to convince her boyfriend Blake Shelton to permanently ditch meat from his diet to help him lose weight.

The 'Hollaback Girl' hitmaker follows a mostly vegan diet and she has been trying to convince Blake, 43, to fill his plate with more fresh vegetables and less of his favourite food, beef.

A source told the new issue of Globe magazine: ''Gwen's told him the way to lose it is to stay the hell away from meat and bad carbs.

''Blake's up to 250 pounds and wants to lose a minimum of 20 by the end of summer.''

Country music star Blake - who has been reunited with Gwen on 'The Voice' after she returned as a coach for the new season - is keen to follow his girlfriend's lead and get healthier but he struggles to keep up with the 49-year-old singer's high energy workouts and is reluctant to give up the caloric treats he loves like steaks and burgers and beer.

The source added: ''He's had a hard time keeping up with Gwen over the last couple years. She's totally into her workouts and vegetarian diet and staying healthy. Her stamina amazes him.''

However, Blake is making a big effort to follow Gwen's lead and is filling his plate with more salads and less junk food in a bid to lose the excess weight and impress the No Doubt star.

The source said: ''He knows he's got to shape up and give up the fast food and beer if he wants to impress his girl. Giving up his meat and potatoes makes him sad, but he'll do it if it pleases her.''

Gwen previously spilled on the secret to her super-hot body, admitting she can only maintain such a fantastic figure by torturing herself in the gym and ditching any food made from animals from her diet.

The mother-of-three - who has sons, Kingston, 13, Zuma, 11, and Apollo, five, with her ex-husband Gavin Rossdale - said: ''There is no secret: You just have to eat healthily, work out, and torture yourself!''