Diet soda, and processed foods, are full of empty, worthless, harmful calories.
Losing weight is a matter of both the quantity & quality of your calories.
The truth is that ‘fats do not make you fat‘.
It is actually sugar that makes you fat.
This is why, when you eat large amounts of processed & hi-sugar containing foods, you’re still hungry afterwards. Your body has not received what it needs.
But when you eat good quality calories, you feel satiated and balanced.