Victoria's top cop has spoken about his struggle with health for the first time since returning from six weeks' sick leave for a "fatigue-related" illness.

Chief Commissioner Graham Ashton said he had been overweight and struggling with burnout when he took extended leave on November 25.

Victoria Police Chief Commissioner Graham Ashton.

He lost 10 kilograms over Christmas and returned to work on January 8 with renewed focus on his physical and mental health.

"I'm feeling a lot better than I was," he told 3AW's Neil Mitchell.