Defining a patient’s body weight in order to calculate their protein and energy prescription is an important step for physicians and dietitians working in the field of kidney diseases. Ideal body weight embraces two concepts. It is defined both as “the goal weight at which nutritional requirements are met” and “the body weight associated with the lowest mortality for a given height, age, gender and frame size”. Both definitions are not generalizable to people living with chronic kidney disease (CKD) and there is no agreed method for how to define ideal body weight in CKD.