remember boxing/ boxing training involves soo much cardio, not to mention strength and resistance training.
most of these guys that look really lean and ripped probably eat a deceivingly high amount, just to stay fueled and maintain their energy.
unless you train like a boxer, it may not be a great idea to eat like one necessarily. at least in terms of volume and calories
but with THAT said, i agree with the breh above. high protein, lean meats, low sugar, maybe some carbs. a chicken and broccoli diet if you will. and adjust your calories accordingly.