What would happen if a person was just over300lbs. lost it all from an eating...

[the_who64]

...disorder then gained it all back? I have a 21 year old son who used to weight around 310 pounds then he developed an eating disorder and then through the course of about 2 years went down to about 170 pounds then a year later went up to 282 pounds after he got help for his eating disorder which was sort of on and off, he has stopped purging is is eating and is keeping it down but before he did it had gotten so bad that he was fainting in the house and in public because he had an electrolyte imbalancement and had dangerously low potassium, he is better now since he got back from getting treatment. He has been eating not very healthy and is getting cravings for unhealthy foods. I am just wondering if there are going to be any permanent side effects as well if there is going to be any problems for him down the road, his potassium is in normal levels and his electrolytes are fine but with this rapid weight gain I am just a little concerned about the physiological effects of this major drop and gain. I trust him enough to know that he isn't going to relapse and he hasn't shown any signs of relapse, he got back at the end of september. If anyone has any advise to give please let me know.