It's less clear how much vitamin D you need if you are overweight but not obese, but somewhere between 2,000 and 4,000 IU is a safe bet,
says Dr. Holick.
According to Dr. Holick, obese people(those with BMIs above 30) require
two to five times the vitamin D that lean people need- a dosage that should be monitored by a doctor,
Holick noted:“Studies have shown that if you improve your vitamin D status,
it reduces risk of colorectal cancer, prostate cancer, and a whole host of other deadly cancers by 30 to 50 percent.