I drink diet lemonade and Coke every single day ...you can't blame your drink for over indulgence. Every food, including straight protein, spikes insulin levels...that's what the body is designed to do. However aspartame does not. It may affect different pathways in the brain for some people reducing your inhibitions but there is no scientific evidence to support the theory that a sweet taste without sugars spikes insulin in humans ... http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=7921865