Unequivocally; yes, this is harmful. You are not a doctor, and should not be giving medical advice. Neither am I but you certainly have not known or worked wit

Unequivocally; yes, this is harmful. You are not a doctor, and should not be giving medical advice. Neither am I but you certainly have not known or worked with people who have done this kind of lifestyle transition. That level of calorie deficit requires medical supervision because the potential complications are life threatening. They don't say 'less', its 500-1000 calories. Your kidneys, liver enzymes, and a number of other factors must be healthy before this can even be considered, and you must be using a nutritionally complete supplement each day for shakes and drinking a lot of water while also taking anti-gallstone medication. They run blood tests weekly to confirm this for as long as you are in the program. I've people who I've worked with who did this. Some people develop gallstones on these low calorie diets, it gets stuck blocking the duct, requires surgery to correct. You can potentially die. You can have a gallstone attack and other complications if you can't slowly ween yourself off the supervisory diet. Suddenly transitioning from no food to 3,000 calories in a hunger haze can cause your organs to shut down. Ask a doctor, they'll tell you and set you right.