This diet theory, consisting of 10% or less of daily calories from fat, is the flip-side to Atkins, Keto, and Paleo. Proponents of the ultra-low-fat approach adhere to a diet rich in plant foods, low in animal products, and high in carbohydrates (80% or more of daily caloric intake). An example of this type of theory is the TLC (Therapeutic Lifestyle Changes) Diet created by the National Heart, Lung, and Blood Association with the purpose of helping people combat heart disease, lower cholesterol levels, and prevent digestive problems.
Ketosis is the metabolic basis for all “keto” or “ketogenic” diets. On a normal diet that includes carbohydrates (sugar and starchy foods), the body transforms these carbs into glucose, which is used as the body’s main source of energy. But, when we consume a minimum amount of carbs, the body will look elsewhere for that much-needed energy, and that “elsewhere” is fat. In short, when the body goes into ketosis, it is burning fat instead of carbs.
The best low-cal diet plan isn't a diet so much as it is a method. CICO stands for "calories in, calories out" and is based on the mathematically sensible principle that as long as you're burning more calories than you're eating, you'll lose weight. All you need to get started is a way to track your calories—there are plenty of apps on the market although a pen and paper works great too—and a food scale to keep you honest about your portion sizes. (Also read this guide on how to safely cut calories to lose weight.) People love the simplicity and straightforwardness of the plan. And while it may not be the fastest way to lose weight, you're guaranteed to have success long term. (Just know that some weight-loss experts actually don't recommend calorie counting.)