Classical "low calorie" diets generally provide somewhere between 800 and 1800 daily calories. Above about 1800 calories the distinction between a deliberately "low" calorie diet and macronutrient-restricted diets begins to blur. Perhaps the most commonly encountered calorie limit for diets is 1200 per day. Many people have tried such diets.
People following moderately low calorie diets generally feel hungry and this sensation grows more intense the longer people adhere to this calorie limit. Interestingly, this sort of hunger may not accompany very low calorie diets like protein sparing modified fasts because those radical diets induce a metabolic condition called ketosis which reduces appetite. Unfortunately, diets above roughly 1200 daily calories induce little ketosis and therefore leave people increasingly ravenous and this is the principle problem with such diets. In the end, moderately low calorie diets are effective as long as people follow them but following them becomes increasingly difficult as appetite grows.
Thus it is the essential criterion of liveability that low calorie diets fail to satisfy and this failure has caused them to fall into deserved disfavor. The only circumstances under which I will prescribe a low calorie diet for a patient is when the patient has an urgent need for rapid weight loss in order say, to undergoe bariatric surgery or because of extremely brittle type-2 diabetes and then, in those rare circumstances, I generally prescribe a protein sparing modified fast.
Otherwise, low calorie diets are rather barbaric and totally fail to recognize that patients are human beings who get hungry and not robots that can simply "dial-in" a daily calorie limit.