DEAR DR. DONOHUE: I am writing in regard to how in the heck you figure out body mass index. I am a male 5 feet 9 inches tall and weigh 180 pounds. People are always hollering that my weight is too much. Is it, according to body mass index? – A.W.

ANSWER: A few fairly simply arithmetic manipulations give you body mass index – BMI – which is a better estimate of obesity than is the weight read from scales.

Take your weight in pounds and divide it by your height in inches. Divide that answer once again by your height in inches. Then multiply the result by 704.

Here is how it’s done for you: 180 divided by 69 is 2.6. 2.6 divided by 69 is .038. That number multiplied by 704 comes out to 26.8.

A normal BMI falls between 18.5 and 24.9; one between 25 and 29.9 is considered overweight; anything greater than 30 is obese.

You’re in the overweight category, but you are not so overweight that people should be hollering at you.

The BMI is a better indication of health than is weight in pounds. However, it is not reliable for people shorter than 5 feet or for those who are extremely muscular, like football players and bodybuilders.

Canadians who are used to metric measurements can figure out their BMI by dividing weight in kilograms by height in meters squared. The norms are the same.

DEAR DR. DONOHUE: For a woman of 87, I have few complaints. I drive, do my own shopping and do just about everything I did when I was 30 years younger. One thing bothers me: I have trouble getting out of a chair. I see you write about exercise. How about giving me some exercises that can get me up and out of a chair? – L.D.

ANSWER: Your question is such a common one that even though I have addressed it before, I don’t hesitate to repeat it.

You need to strengthen your quadriceps muscles, the ones on the fronts of the thighs.

All the equipment you need is a kitchen chair. Stand in front of the chair just as you would to sit. Your feet should be shoulder-width apart. Cross your arms over your chest. Leaning forward slightly, lower yourself as you would to sit down, but don’t actually sit. When you are only an inch or so above the seat, hold that position for a few seconds and then return to the standing position. Repeat 10 times, rest for a minute and do another 10 repetitions.

If this is too hard, put a couple of pillows on the chair so you don’t have to lower yourself quite so far. If 10 repetitions are too much, start with one or two.

For the second exercise, sit in the chair. Your feet should be dangling, not on the floor, so you might have to sit on pillows. Straighten your left leg and hold it outstretched for two or three seconds. Relax it and switch to the right leg. Do 10 repetitions of both legs. Take a minute break and repeat the exercise. Again, you don’t have to do 10 repetitions from day one. You can start with one or two.

DEAR DR. DONOHUE: I have three boys. All play football. The oldest boy lost a tooth last year while playing, and my dentist read me the riot act for not saving his tooth. I was there when it happened. His two brothers are playing this year. What am I supposed to do if it happens again? – R.C.

ANSWER: Rinse the knocked-out tooth in clear water. Don’t scrub it. It has ligaments clinging to it, and those ligaments can help re-establish its mooring in the tooth socket.

Try to put the tooth back in its socket. If it goes in easily, have your patient bite on a gauze pad until he sees the dentist.

If it doesn’t go into the socket easily, put it in milk, salt water or plain water. Or, you can tell your son to slip it between his cheek and gum.

Get to the dentist quickly. If the dentist is able to work on it within 30 minutes, the chances of saving the tooth are excellent.

DEAR DR. DONOHUE: I live in fear of ovary cancer. I have no relatives who have had it, but I had two friends who died from it. Is there any test I can take to detect this cancer? – C.R.

ANSWER: It’s reasonable to respect all cancers, but it is not healthy to dwell on one to the extent that it turns life into a nightmare. Only about 25,400 new cases of ovarian cancer are diagnosed yearly in North America. Your chances of getting it are not great.

Having used birth control pills, having been pregnant and having nursed an infant serve as protections against ovarian cancer. All of these situations suppress estrogen production. Never having a pregnancy or having a mother, sister or daughter who has had ovarian or breast cancer places a woman at greater risk of developing it.

In its early stages ovarian cancer produces few to no symptoms. As it grows and spreads, women often complain of bloating and feeling full when they have eaten only a few mouthfuls. The abdomen frequently enlarges. Pelvic and back pain are other symptoms.

By the time symptoms appear, the cancer has spread in close to 70 percent of patients. Because of late diagnosis, the cure rate is not encouraging. If, however, the cancer is detected early and treated, there is an 80 percent or greater chance of cure.

There are no good detection tests for this kind of cancer. You might have heard of the blood test called CA-125. It was originally thought to be a good detection test for ovarian cancer, but it has not panned out. It is, however, a good test to follow treatment of the cancer. A new test, OvaCheck, should be available by the time this is printed. Its place in early discovery of ovarian cancer has yet to be determined.

Ultrasound pictures of the ovary are another way of discovering the cancer. No official body has recommended screening ultrasounds for the average woman. For women at high risk of having cancer because of family history, ultrasound is often suggested.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.