Why diet never works for anyone

According to discovery channel, anyone whom diet and lost 100 pound they will regain it within 5 years. This is due to the body is confuse between famine and diet. When we diet, it is telling the body that we are experiencing famine, and our defensive mechanism fights back by releasing Ghrelin, a type of hungry hormone to improve appetite. This defensive mechanism is a fail safe just in case if anyone whom wanted to starve them self to death. Therefore dieting never works in the long run unless with determination and discipline. Therefore most doctor do not ask obese people to diet instead they ask them to change their lifestyle. Every person body is differ from another and there is no single cure for all. For some just change their eating habit would just cut it, for some exercising helps bringing it down and some just move around more would have just cut it.