Is sugar inherently fattening on an isocaloric diet?

I have a 305 squat, 330 deadlift and 160 press (5s) at 6'0 and about 255, but body composition is changing as I continue training.

I get 3800-4000 calories daily, about 270g of protein, 50g fat and near 600 carbs, which includes 1 cup of organic sugar. I know, crazy.

I dont feel as though my body is changing enough given the calories and training, and I am getting stronger, but I wonder about the sugar.

Is it simply fattening or have I just not given this enough time?

Get a 430 deadlift and see what happens.