Usher's son battling diabetes

R&B star Usher has been paying closer attention to his son's diet after he was diagnosed with diabetes.

The Burn hitmaker has not revealed which of his two boys is suffering from the blood sugar disease, but he admits the health condition has taken its toll in the past year, as he also mourned the loss of his beloved grandmother.

He tells breakfast show Today, "This year has been really one of my hardest years - I lost my grandmother, my son was diagnosed as being a type one diabetic. It has definitely been a difficult one for me, man."

And Usher admits he spends a lot of his spare time reading up on his son's dietary requirements to ensure he is staying healthy, even when he's on the set of reality show The Voice, on which he serves as a judge.

He adds, "Sometimes you're looking at me and we're off camera, and I'm online looking at numbers, trying to make sure he's eating properly. It's crazy."

Usher is father to six-year-old Usher Raymond V and five-year-old Naviyd, from his marriage to stylist Tameka Foster.