Oooh, let me at your group and I'll kick 'em into touch for you!
They're just trotting out scare-mongering myths without any understanding of the facts.
Firstly, this diet is for anyone who is at all "overweight" (ie a BMI above 25). You don't have to even be obese. It's totally approved by doctors and you can't even go on it without the say-so of them or a properly trained pharmacist who will check your medical history and monitor you throughout. If it wasn't safe for you, they wouldn't let you start.
Yes it eats into your glycogen stores, but that's a good thing. Glycogen is a short-term sugar store that your body creates so it can quickly and easily access energy. The ideal situation for our bodies is that the calories you eat equal the calories you burn. That way, your body only ever needs to have that short-term fuel supply. If you eat more calories than you burn, then your body converts the excess glycogen into a longer-term store of fat. That's what we've all done in the past and why we're now here.
The body will always get its energy from the most accessible places first. Totally common sense. Glycogen is the easiest to get at, and fat is more difficult. The only way to get rid of fat is to first get rid of the glycogen.
The only time your body will try and get energy out of muscles is once it has COMPLETELY depleted all the glycogen and all the fat. Bodies aren't stupid. They're not going to damage themselves if they can help it. Think of bears in hibernation - they overeat to get themselves good and fat for the winter and then their bodies use it all up during the time when they've no calorie intake. When a bear comes out of hibernation it's skinny and raggedy as anything but it's still got all the muscle it needs to immediately start hunting stuff down to eat. Don't mess with a hungry bear - they're still strong enough to kill you with a single blow and then rip you to shreds!
As for hair falling out, well yes - hair falls out all the time! Usually the rate it re-grows keeps up with the rate it falls out so no-one really bothers. While you're in ketosis, you MIGHT have a slower re-growth than usual and end up thinking it's going thin. Again, it's just the body being clever and not wasting energy doing something that's not terribly important (in survival terms, anyway). If that's the case (and it by no means happens to everyone) then it will start growing at the normal rate once you go back to eating. A very minor and short-term inconvenience at the worst.
Putting the weight back on may or may not happen. That's got NOTHING to do with which diet you're on, though - it can happen with all of them. It depends totally on whether you can change your old eating habits (and keep active). Personally, I think this sort of diet actually helps. Most diets mean you psychologically deprive yourself and feel rubbish about the rabbit-food you're having. You can't wait for the diet to be over and then you can go back to eating "proper food". By cutting out food completely, however, it will physically alter you - get rid of toxins and clean out your tastebuds - which will help change the things you WANT to eat in the future. Very importantly, it also gives you the opportunity to stand back and look at things from a different perspective. You'll notice your psychological responses to triggers and recognise them for what they are. If you have a sudden craving or a temptation, take the opportunity to figure out what caused it. Was it an emotional trigger - stress or anxiety, perhaps? Time of the month? Sheer opportunity - seeing the food right there in front of you when otherwise you might never have even thought about it?
These things may well build up over time - don't expect to re-educate yourself straight away, but try and stay alert for signals and think about what your body is saying to you. It's all good. Even the days when you feel stressed and crappy - they're great opportunities to learn about the real you. Once you understand yourself and your relationship with your food, you'll be better able to take back control.
Eeek - well done if you've stuck with me so far...!
Finally, I'll just echo Dee and say absolutely - being overweight is much more dangerous. Not just physically, but also mentally. I was quite severely depressed when I started this diet, for all sorts of reasons and I thought the weight was merely a slight contributing factor... Now that I've lost a couple of stone I can't believe what a difference it's made to my mood and my confidence levels! I'm not back to normal by any means, but I'm in such a better place and I feel able to deal with the other crap so much better. I'm getting my life, and myself, back! It's the best thing I've done in years...
All the best, :bighug:
Marianne x