I drink three 20-ounce bottles of Diet Coke every day. It has no discernible impact on my weight loss efforts. What it does do is to wake my sleepy butt up. Right now, I freely admit being addicted to caffeine and I also freely admit that I have no intention of cutting it out or cutting back. The times in my life that I haven't had caffeine have been awful. I get severe headaches to the point of vomiting. I'll pass on that.