If you're eating tons of added sugar and refined carbs, it's not necessarily the empty calories you need to worry about that leads to weight gain. Jason Fung, MD, a nephrologist, explained in a previous interview that eating processed carbs and sugary foods such as doughnuts, crackers, pasta, white bread, and alcohol spikes your insulin levels, which can cause weight gain. Keeping your insulin levels low will help reduce your overall body fat percentage, and that includes belly fat.