When you eat high-sugar foods and refined carbs like candy and doughnuts, they won't help you lose weight, but it's not only because those foods tend to be high in calories. It also has to do with insulin.
Jason Fung, MD, a nephrologist (kidney specialist), explained that processed carbs and sugary foods such as ice cream, cookies, crackers, and regular pasta spike your insulin levels, which causes weight gain. High levels of insulin in the blood block leptin signals (the "I'm full" hormone) to the brain. Your brain doesn't see that you are full, so it thinks you're starving and increases hunger so you eat more.
High insulin levels also cue your body to store fat, which obviously won't help you lose weight. Keeping your insulin levels low by limiting these types of foods is a simple way to help reduce your overall body fat percentage.