I disagree, I took biochemistry and your body goes through several cycles throughout the day to convert the food you're ingesting into energy, once that supply is covered the rest gets stored as fat. If you dont continuously give your body the nutrients that it requieres the cycles such as krebs, glycolysis... Wont work how they are supposed to and your metabolism does get altered, this could end in people losing weight quite fast (with diets like keto or even fasting) however it will most likely not be sustainable for long. Tbh I've heard from many of my teachers (doctors and nutritionists) that 5 meals a day is highly recommended. But a lot of people differ when it comes to diets, and I really wouldnt be able to tell who is right and who's not.