We know what you're thinking - now food you don't even really eat is dangerous? Bear with us here while we try to explain why chewing gum has made the list. Commercially available chewing gum has typically been sugar-free for decades now. But sugar alcohols and artificial sweeteners are still present and they're not good for you. Sugar alcohols in particular can cause digestive problems, bloating, and flatulence. Is chewing gum worth all that embarrassment? You don't even get to swallow it!
As for the artificial sweeteners, even though you're not swallowing the gum, they're still triggering your body's receptors and you'll find that you'll often be hungry or have a craving for something sweet afterwards. Try giving up chewing gum altogether. If that's not possible, you could start snacking on something low calorie like sunflower or pumpkin seeds.