 [ Symptoms ] how was maximum heart rate determined  your target heart rate calculator page claims to calculate the highest safe heart rate during exercise using the formula 220 minus age for maximum heart rate i thought haskell and fox made up that formula in 1970 from 11 experimental studies of maximum attainable heart rate and no subjects were harmed in these experiments if that is so that formula has nothing to do with safety am i right if not what studies were used to determine what heart rate is safe [ Disease ] weight loss can be related to abnormal thyroid functions leading to increased level of thyroid hormones or hyperthyroidism that can lead to weight loss secondly frequent mensus can be due to causes related to reproductive system like hormonal imbalances ovarian cysts etc approaching menopause can also cause similar problems so consult a gynaecologist and get a thorough evaluation done along with investigations like cbp hormonal profile pelvic ultrasound etc hope this helps