For the purpose of definition, a diet is time that calories consumed are reduced below calories burned. To say that diets don’t work is in fact not accurate. Calories that are consumed are less than calories burned, weight loss will occur. It doesn’t matter much which diet (this can be argued endlessly though) or which combination of foods (this too can be argued).
To say that it is hard to impossible to stay on a diet where the person feels a high level of sacrifice or hunger, that is accurate. This is where the Yo/Yo effect comes in. The weight loss achieved will actually be gained back than the weight gained in the first place.
Our goal is to provide a viable and acceptable lifestyle where once the weight desired is obtained, the weight can be kept off using a high protein diet. This is the balance between sacrifice and reward, keeping blood sugar levels stable. If the weight is kept off then one will experience a much higher level of energy and desire to be active which helps the cause of burning calories while not starving or suffering.
In the end, it is about subtle lifestyle changes that are acceptable and not too excessive. It is about what works for each individual.