This refers to the mythology of weight loss. Everyone's method they implement to lose weight is different. I count calories based on hitting certain macronutrients. Some people count points with weight watchers. Some people do Keto. All diets have one commonality: eating less over an extended period of time. This is calorie expenditure. Calories in vs. calories out. Diets are anecdotal because of the method for weight loss one chooses to implement based on their own observations about themselves. Take 2 people that want to lose weight. Person A observes that intermittent fasting works for them. Person B observes eating once per day works for them. Both methods work. What works for one (method) may not work for the other (based on many variables). So, how is it possible both people could lose weight? They were in a calorie deficit.