a condition in which a greater than normal amount of fat is in the body; more severe than overweight; having a body mass index of 30 or more.

obstetrician (ob-steh-TRIH-shun):

a doctor who treats pregnant women and delivers babies.

ophthalmologist (AHF-thal-MAH-luh-jist):

a medical doctor who diagnoses and treats all eye diseases and eye disorders. Opthalmologists can also prescribe glasses and contact lenses.

optician (ahp-TI-shun):

a health care professional who dispenses glasses and lenses. An optician also makes and fits contact lenses.

optometrist (ahp-TAH-meh-trist):

a primary eye care provider who prescribes glasses and contact lenses. Optometrists can diagnose and treat certain eye conditions and diseases.

oral glucose tolerance test (OGTT):

a test to diagnose pre-diabetes and diabetes. The oral glucose tolerance test is given by a health care professional after an overnight fast. A blood sample is take, then the patient drinks a high-glucose beverage. Blood samples are taken at intervals for 2 to 3 hours. Test results are compared with a standard and show how the body uses glucose over time.

oral hypoglycemic (hy-po-gly-SEE-mik) agents:

medicines taken by mouth by people with type 2 diabetes to keep blood glucose levels as close to normal as possible. Classes of oral hypoglycemic agents are alpha-glucosidase inhibitors, biguanides, D-phenylalanine derivatives, meglitinides, sulfonylureas, and thiazolidinediones.


see tolbutamide.


an above-normal body weight; having a body mass index of 25 to 29.9.

Get our free newsletters

Stay up to date with the latest news, research and breakthroughs.