If you have gained a great deal of weight in a short time it's pretty likely the weight gain was a side-effect of medication prescribed by your doctor

See prescribed steroids and HRT

and amitriptyline

Lose weight, reduce your risk of most cancers, high blood pressure, type 2 diabetes, stroke, heart disease, heart attack, vascular dementia, osteopenia, osteoporosis, hypercholesterolaemia, depression, liver and kidney problems, and improve your health in many other ways without drugs, hunger or expense by eating less salt! - Try it! - You will feel so much better!

Read my Mensa article on Obesity and the Salt Connection

And see Sodium in foods