I agree mostly with the post above.
I think it will mainly be due to the low nutrition you'll have been getting and the stress that will have put on your body as it does end up where your body basically breaks down your muscles to get energy. Because of this they lose their strength and are more susceptible to cramping. Alongside this people with EDs often have electrolyte imbalances which again can be a major source of cramping. As well as this, if you've not been eating healthily for some time, even if your eating patterns have improved now, it is likely that your body will have little energy and what it is getting will be going straight to your heart/ brain alongside other organs and also being stored so your body is preparing itself for if you stop eating again. This means you'll have little energy for any kind of activity which can literally be just walking a couple of steps or standing up as your muscles do have to work quite hard for that (several have to contract at the same time and at the right level for this to occr properly and if they don't this can also case cramp).
You do need to rest up really but as well as that you do need to go and see a doctor and make sure this is the problem and nothing else can go wrong.
Really, if you have osteoporosis the main cause in girls/ pre-menopausal women of a low body weight is that their periods stop. Your ovaries stop producing oestrogen and in people oestrogen is needed in part to get Calcium into the bones. Because of this calcium (or Vit D) supplements will not usually help with this and the best way to be truthful is to get therapy to replace them (such as Hormone Replacement Therapy (HRT)) or better than that is your periods restarting but for that to occur it basically means you need to gain quite a bit of weight which I know will be very hard and will also take a long time. Osteoporosis in itself is not a painful condition. However it significantly reduces the strength of the bone (the name simply translates porous bones ie. holes in the bones) and therefore makes them much more likely to break (it is the reason old ladies who have gone through their menopause and not creating oestrogen to high enough levels any more often break their hips when they fall) and healing will take longer, it will not be the case of what you're experiencing right now but is likely to be occurring within you to some degree if your periods have ceased due to low body weight.
I'd advise you to read the
ED Article which MANY people find useful and it should help to answer some of your questions as well as highlighting the risks of ED-related behaviours. It is written in a behaviour based way rather than different EDs so people can specifically look up what they're doing and how that may affect them.
