Flexible dieting is just that, a flexible approach to dieting that is about focusing less on food name, and more so on food composition ie. what foods are made up of in terms of the macronutrients, micronutrients and fiber. It aims to provide a practical solution to dieting which is maintainable in the long term such that it will provide sustained results.
Flexible dieting simply involves daily calorie and macronutrient targets whereby you eat foods that allow you to reach those daily targets. It is merely a system of quantification that allows you to measure your intake according to your desired goal. Think of it this way, if you were to build a house, would you do so without using a tape measure? No, because it would be a very inefficient and inaccurate way to build a house, so why would you try and build your dream body without tracking your macros?
Macronutrient tracking is like the tape measure for building your body, it allows you to measure and track everything that goes in, in order to build your body in the most efficient and effective way. It eliminates all the guesswork of conventional dieting and ensures you are heading in the right direction.