You've decided that you want to become a pilot. You have a school all picked out, you have time set aside, and you have the funding necessary to complete the training. What now? Before you can actually start flying, you need to be medically cleared. To do this, you must first determine what class medical certificate is required for the type of training you are starting. The FAA separates these into three classes: 1st, 2nd, and 3rd class medical certificates, with 1st class being the most stringent and 3rd being the least.
3rd class certificates are usually reserved for the general aviation pilot, while 2nd and 1st are reserved for the commercial pilot and airline transport pilot, respectively. The minimum requirements for 3rd class pilots are as follows (paraphrased from FAA Guidelines Section 67):
The pilot must have visual acuity of 20/40 or better in each eye with or without corrective lenses, the ability to distinguish the colors necessary to perform the duties of an airman, and have no acute or chronic condition that interferes with the proper function of the eye or eyes. The pilot must also have a hearing test and score 70% on a discrimination test (basically tell which side the sound is coming from), and have good equilibrium. THIS DOES NOT PRECLUDE INDIVIDUALS WHO ARE DEAF OR HEARING IMPAIRED FROM OBTAINING A PRIVATE LICENSE. There are provisions for these individuals, however they must fly with another certified pilot. The pilot must also have no diagnosis of any mental condition which manifests itself by overt acts, which includes but not limited to: bipolar disorder (or other personality disorder which may cause the pilot to be dangerous in the air), psychosis, hallucinations, and substance dependence. A substance abuse test is required as well.
Other conditions that will preclude one from obtaining a 3rd class medical certificate are neurological conditions such as epilepsy and cardiovascular conditions including but not limited to angina pectoris and having a pacemaker. Diabetes requiring insulin injection is also a factor that will preclude a person from obtaining this certificate. The medical requirements for 2nd and 1st class medical certificates are more stringent, but the main difference is that the eyesight/visual acuity and hearing requirements are higher.
Once you determine what type of medical certificate you need for your training, you can then find a physician that is certified by the FAA to medically certify you to fly. My suggestion is to try and get the 1st class medical certificate. You can become a private pilot, a commercial pilot, and an airline transport pilot with a 1st class certificate, but you can only become a private pilot with a 3rd class medical certificate. If you are not able to obtain a 1st class certificate, the doctor will give you the highest medical certificate that you are medically qualified for. The FAA website (www.faa.gov) has a link on their main page that will direct you to a search engine where you can find physicians in your area that are FAA-certified. I was lucky and my primary care physician happened to be FAA-certified.
Another thing to consider is your weight. I am about 45 pounds overweight, and have to take that into account when I fly. Being overweight will not necessarily preclude you from obtaining a medical certification, but the future medical conditions that are caused due to your weight may.