Thanks for putting your query over here.
I have gone through your question and understand your concern.
The information you provided seems incomplete.
Want to know how much is your body mass index?You have to loose 80 means what is your present weight?
The cause of your
overweight is likely due to
thyroid disorder as you said.Proper follow up and medication for the underlying medical disorders you mentioned will itself help putting on excess weight.Also fasting for 17 hours is really a bad option of loosing weight.You just need to have a routine balanced diet and avoiding fried,processed,excess sugary or salty,refined food.(1500 calorie intake daily is fine in females,for males,it should be minimum 1800 calorie intake daily)
Take routine follow up and medication for your
meniscal injury.Ask your treating doctor as when you can start walking because walking is best exercise in your age.
Loosing 6 pounds in 4 months is not less.Important is you should have gradual
weight loss of atleast 0.5kg per week in healthy way.
All this is true only if you don't have
morbid obesity (Body mass index more than 40) otherwise the line of action changes.
Thanks and regards.