Since arriving at the Broncos two years ago, Gillett has added 10kg to his frame. He put on 3kg in recent months with a diet in which he eats every two hours.
The 22-year-old played backrow, centre and five-eighth last year but hopes to finish his career in the forwards.
''My plan for this year is to cement a spot in the backrow. If not, I'll play the same role I did last year but I've been training in the second-row and that's where I'd like to stay,'' he said.
''They (Broncos coaching staff) have asked a lot of us to put on some weight so I'm at 104kg now. It's the heaviest I've been.
''Among the forwards, me and Corey (Parker) were the lightest ones so we needed to add a bit more size. I'm not eating huge meals; my breakfast, lunch and dinner are good meals but in between I'm having a lot of protein and keeping my fluids up.