I’ve been favoring fish, protein, and veggies for some time, and trying to prefer lean meat, and I’m surprised at how flabby just one greasy meal or large soft

I’ve been favoring fish, protein, and veggies for some time, and trying to prefer lean meat, and I’m surprised at how flabby just one greasy meal or large soft drink will make me feel. I can’t really explain it, but it’s like once my body became accustomed to the current diet, I can now feel when I deviate from it. Still haven’t found any evidence for what I’m feeling though.