When you eat far fewer carbs, your body begins to burn fat for fuel. This can put your body into a metabolic state called ketosis. In this state, your liver turns fat into small energy molecules called ketones, which your brain and other organs can use for energy. Eating a diet lowers insulin levels, often dramatically, which can help you access your body fat stores for energy. Many studies show significant weight loss on keto, without having to count calories.
To see this working, head to your live site.