This is a plain and simple fact; it doesn’t matter how much you lift or exercise, if you’re not incorporating your diet, you’re only doing half the job. Your results will be minimal at best. This is true for all body types, and for all goals.
If you’re skinny and struggle to gain weight, you want to eat 1.5 grams of protein per lb of body weight, and as much starchy carbs as you can get all day long. The carbs will trigger your body to store fat and protein, but you have to eat more than your freakishly fast metabolism can burn through to achieve results.
If you’re fat, you want between .75 and 1 gram of protein per lb of lean body mass, and no more than 30 grams of carbs per day. You want to preserve your muscle mass with the protein, while denying your body its first choice of fuel, carbs.
If you’re in the middle, you probably don’t need to worry much about diet, but that’s taking the lazy approach. Why settle for good enough when you can be amazing? God blessed you with the Holy Grail of genetics and you’re gonna squander it? No, asshole! You owe it to us fatasses and scrawny twigs to be a step above. If for no other reason than to give us something to aspire to.
The bottom line is that we are all busy adults, with jobs, friends, family, and churches that demand our time and attention. It is a sacrifice to get into the gym. But it is a necessary sacrifice. If you don’t want that time spent to be in vain, you need to do the rest of the work. Get your diet in check.