I lost 70 pounds over about four months last year primarily via calorie counting. I know it's anecdotal, but I absolutely felt hungrier after the same meal if I had a diet soda with it compared to an unsweetened iced tea, or even an iced tea with a sugar packet or two. It's great that you have the willpower to stick to the rest of your diet regardless, but there is definitely a reason people recommend cutting it out to make it easier to follow a plan.