Blake Shelton hates working out.

The 'Voice' USA mentor, who has been showing off a trimmer physique since divorcing Miranda Lambert in July after four years of marriage, has overhauled his diet in favour of killing himself in the gym.

A source close to the 39-year-old singer said: ''[He] hates working out but does run on the treadmill sporadically. Most of the weight he lost is from him trying to eat better. It happened gradually.''

The country music star recently admitted he went on ''the divorce diet'' following his split from Miranda, adding: ''The whole stress of getting through all of that is just weird.''

The avid junk food fan is now sticking to a healthy diet and loves lettuce-wrapped burgers.

Meanwhile, Blake ''hasn't had time to think about dating,'' as he is currently writing songs for a new album due out next year, but hopes to find a new relationship eventually.

The insider told Us Weekly magazine: ''He dove right into work after the divorce. He wants more balance in the future, but he's enjoying what he's doing. He's very happy.''