Sometimes your excess poundage really is due to a medical condition. One of the top culprits is Cushing's syndrome. The rare disease was first described in 1932 by Dr. Harvey Cushing, an American neurosurgeon who helped pioneer brain surgery [source: Nordqvist].
The syndrome named after Cushing is a complex hormonal condition where the body is flooded with far too much cortisol, the body's main stress hormone. This may occur because of a disorder (for instance a tumor in the pituitary gland), or else you've been taking a lot of steroid-based medications (like the ones prescribed for asthma). In normal amounts, cortisol, produced by the adrenal glands, works to regulate your glucose levels and suppress the immune system.
But get too much coursing through your system, and you may end up with thin skin, bruises, high blood pressure, osteoporosis, diabetes, weakness, a puffy face, fat on your neck and shoulders and, yes, weight gain. Indeed, accelerated weight gain is the main characteristic of Cushing's syndrome
If untreated, Cushing's syndrome can lead to death. However, there are several remedies available, from slowly reducing the amount of corticosteroids taken to surgery (in the case of a tumor) [source: Nordqvist].