High Protein / High Fat Diet:
Very often this type of diet is associated with a high fat intake. It bases its success on a process called ketosis (the process of the formation of ketones). Where the body is trying to obtain glucose, burning fat to obtain it is not successful, since it can not be turned into glucose. Fat then is not completely burned also due to the lack of glucose. The body then obtains the glucose it requires by breaking down muscle protein as well as protein from vital organs. In this whole process and with the fats not being burned completely, a byproduct called ketones are formed. This formation of the ketones is called ketosis. Since it is not a product used by the body, the body excretes it in the urine and breath. The ketones can often be detected with an acetone-like smell on the breath.
Will you loose weight: Yes you will, but again remember what you are loosing: vital lean body mass from the breakdown of the muscle protein and protein of vital organs.
Effects on the body: I must state that this is a very detrimental method of trying to loose weight and I would never recommend this under any circumstance! Ketosis is a very unhealthy condition since the partially burned fats can damage the kidneys. If the kidneys are damaged it can lead to a very dangerous condition called acidosis.
It also causes an increase in uric acid levels in the blood, which may precipitate a gout attack. In Diabetics, if ketosis is observed, it can even lead to hospitalization since it is extremely hazardous to them. Even in pregnant woman, if ketosis is present, the glucose levels in her bloodstream are so low that it can lead to brain damage in the child.
People in a state of ketosis also experience dizziness, headaches and nausea, not to mention the foul smelling breath. It is as I stated before, not a desired method of loosing weight at all and should be avoided at all cost!