Some good points here, but eating "clean" doesn't really become a necessity or make a significant difference unless you're into single digit bodyfat percentages and need to get absolutely shredded. I'm cutting at the moment and I've dropped 20lbs in 5 weeks whilst maintaining muscle mass - I'm still having chocolates and sweets pretty regularly and the odd bit of fatty crap. Main thing is that you track your caloric intake and if you're looking to maintain muscle mass, then get plenty of protein.
Though, obviously, in terms of practicality, complex carbs will keep you fuller for longer and provide sustained energy, and foods high in fats possess a pretty poor food volume:calories ratio (i.e. they contain a high amount of calories per mouthful meaning they're a bad choice for a low calorie meal if you wish to satisfy hunger). So you'll naturally find yourself drawn to sources of food that are pretty clean anyway