The general premise of high-protein/low carb diets is that by cutting carbs and increasing protein, you can lose weight fast. Their key selling point is that you can eat large quantities of meat, fish, eggs, cheese and dairy products if you cut out grains and carbohydrate-dense foods.

Promoters of the diets explain that you lose weight because your body switches from carbohydrate metabolism to fat metabolism; in other words, when you cut out carbohydrates as a source of energy, your body burns its stores of fat instead. This process of burning stored fat for energy is called ketosis. High-protein diets sell themselves by advertising ketosis inducement as a way to lose weight without cutting down on fat intake.

Low-carb diets are okay, provided they're done right - and not to excess. Be aware of any of the following if you try a low-carb diet:

Low energy. Energy from fat is “last resort” energy and does not provide the body and mind with the fuel they need, which is why people on high-protein diets can feel easily tired and can suffer exhaustion

Ketone damage. Ketosis produces ketone bodies. When too much protein is consumed these ketones build up in the body, causing damage to the liver and kidneys. 

Increased uric acid levels and water loss. When protein is broken down and metabolized, it also raises the levels of uric acid in the blood. The more protein you consume, the more of this toxic by-product the body has to deal with. The body pumps a lot of water through the kidneys and urinary tract to try and flush it out. This water loss not only gives a false indication of weight loss, it is also detrimental to the body in many other ways.

Acidosis. Excess protein can cause a condition called acidosis, which can lead to osteoporosis and kidney damage. 

Bad body odor and breath are minor problems reported by followers of high-protein diets. Other common discomforts of a carnivorous diet include constipation, dehydration, dizziness, headaches, mental fatigue, sleep problems and nausea: those are a few bitter pills to swallow with your protein.