Polycystic ovarian syndrome
Accounts for unexplained weight gain in 20 percent of women due to abnormal secretion of a hormone by your ovaries.
Growth hormone dips
If you don’t sleep at least 90 minutes at a time, you would gain weight.
Testosterone drop
Afflicts older men and postmenopausal women. A libido drop is due to testosterone converting to estrogen. Less testosterone also means less muscle mass, which makes it harder to burn fat
Thyroid levels
Hypothyroidism slows down your metabolism