I agree with stort brod eating extreme low carb is not only ineffective but it is also potentially very dangerous to your health, especially if it is under 10 grams of carbs for sustained periods of time.
Not true. Do you have a source for this? Ketoacidosis is dangerous for diabetics, but not ketosis alone for other healthy people.
On an extreme low carb diet, most of the weight you lose will be water weight that is no longer held by your body because it no longer has the carbohydrates in your body which are meant to retain it. And since the body is over 70% water, you can see how important water retention is.
Yes, you drop alot of water at the start of a low carb diet. For every gram of carbohydrate you consume, your body stores 2-3 grams of water along with it. Eliminate the carbs, your body drops water. Water retention is not important, staying hydrated is. Your body is smart though. Drink more water, you urinate more. Drink less water, and your body thinks that you are dehydrated so it retains water.
One of the reasons why the low carb Atkins fad diet was ultimately unsuccesful was two reasons: (1) the weight loss is very fast, but you put the weight back on just as quickly plus with interest and (2) it is rather difficult to maintain a very high protein, high fat, and low carb diet for prolonged periods of time due to lack of choice. There is only so much steak, chicken, bacon, eggs, and fish you can eat without getting bored.
You will only put the weight back on rapidly if you start eating over your maintenance, that goes with any diet. Once you start consuming carbohydrates again, some water weight will be gained back for reasons that I posted above.
I agree that a keto diet may be hard to maintain for some people, but again, it's the same with any diet. The BEST diet for a person is the one that they will stick to.
Secondly and even more importantly, the human brain and vital organs require a bare minimum of carbohydrates to operate effectively. Through his research, Dr. Atkins found that 20 grams of carbs per day were the minimum requirement for effective brain and organ functioning - and even this only for certain relatively short periods of time. On an extreme low carb diet you will lose weight very quickly, but chances are you will gain it all back plus interest, and at the cost of putting your brain and internal organs at extreme risk. As stort bord mentioned, on a very high protein, low carb diet you will feel very sluggish and tired since burning fat is not the optimal energy fuel preferred by the human body. Your workouts will suffer from lower weights, lower reps, shorter routines, and all round less effective workout sessions. Remember, the human muscle is only about 24% protein, much of the rest is water which requires carbohydrates to properly maintain.
When carbohydrates are absent from your diet, your body creates glucose as it needs it. Also when going low carb, ketones are produced by your body as the preferred fuel source (Once adapted to ketosis, your body still only uses ketones for about 75% of it's fuel). The sluggishness you describe is also known as "keto flu". This process can take anywhere from 7-21 days until your body has adjusted to using ketones for energy. Most people don't stick it out and say that they can't function without carbs. I would say if you still feel like sh1t after 21 days, keto is not for you.
A healthy, well balanced diet - although the weight loss will be slower - will always be the healthier, more effective choice.