I've spent a long time in bio/chem and dietetics lol. All it is is an understanding of exactly how many calories i have to work with daily. However, like i previously mentioned, you may have certain hormonal issues from being overweight. For example, here's basically my diet yesterday. My TDEE was roughly 3200 calories. I work a semi-active job, and i'm a basketball referee. My current deficit is 400 calories, giving me 2800 calories to work with. My breakfast was around 500 calories, lunch was small and 500 calories, that pizza and dinner was around 1500 calories, that's still around 2500 calories. I hit 200g protein easily for the day and was under 2800 calories total. The body doesn't see simple sugars and turn them in to adipose tissue. The body doesn't see saturated fat and turn it in to adipose tissue. The body sees excess calories and turns it in to muscle, and stored energy. That's as simple as i can make it haha. I care about total calories (being in a deficit every day), and my protein intake (200g + daily), other than that i do not care about the composition of my fat/carb intake.