DEAR DR. DONOHUE: I’d greatly appreciate it if you would say something about heatstroke. I began running about six months ago, in the late fall. I would like to continue year—round, but the heat here can be unbearable in the summer. What sort of precautions can I take not to get heatstroke? — W.M.
ANSWER: Dehydration makes a person susceptible to heatstroke, so your best protection is staying hydrated. You can lose tremendous amounts of water from sweating. Prepare for such losses by drinking 16 ounces of water an hour or so before you run. Carry a water bottle with you so that you can keep drinking during your run. Weigh yourself before and after exercise. One pound of weight loss is about 1 pint of water, 470 ml. Make up any fluid deficits quickly.
The first sign of heat trouble is heat cramps. They’re a warning to stop what you’re doing, get to a cool place, drink fluids and take some salt.
Heat exhaustion is the next stage of heat injury. In heat exhaustion, blood pools in the legs, so the heart has less blood to pump. That makes a person feel wiped out. The pulse is rapid, and blood pressure drops a bit. Many have a headache and feel dizzy. This is a major warning to stop and get to an air—conditioned place where you can hydrate yourself.
The calamitous heat injury is heat stroke. People cannot treat themselves for this. They’re too out of it to do anything. Body temperature rises to 104 F (40 C), the pulse is fast and weak, and sweating stops, so the skin is dry. Treatment is total immersion in cold water.
You don’t have to be active to suffer major heat complications in hot weather. In the heat wave that struck Europe in 2003, up to 70,000 excess deaths were recorded, and many of those deaths were older people stuck in homes with no air conditioning. If people find themselves in such a situation, they should try to find an air—conditioned environment or at least have a fan blowing on them. They ought to drink fluids even if they are not thirsty.
DEAR DR. DONOHUE: How do you estimate what your daily calorie intake should be? I am a 35—year—old woman who weighs 155 pounds. I am 5 feet 4 inches tall. I have no idea what an appropriate calorie intake should be for someone of my age and size, or how many calories I have to cut out of my diet to lose weight? — K.J.
ANSWER: The answer to your question isn’t a precise one. You have to figure how many calories your body burns by just existing (the basal metabolic rate) and how many calories you burn through physical activity. Lots of this is guessing.
Last year, the University of California, Berkeley, Wellness Letter published the daily calorie intake needed to maintain the weight of a 50—year—old, 140—pound woman and a 50—year—old, 175—pound man. For the woman, it is 1,800 calories if she does little physical activity, 1,960 calories if she does moderate activity and 2,200 calories for strenuous activity. The corresponding man’s numbers are: 2,350, 2,560 and 2,900. For people younger than 50, increase the calorie count by 10 percent; for those older, decrease it by 10 percent.
To lose a pound a week, decrease the daily intake by 500 calories.
DEAR DR. DONOHUE: Your answer to E.A., who had been exercising while on a water—only fast, said his exercise would not kill him. I saw an article by a doctor who had done thousands of autopsies, and he said when apparently healthy individuals died without finding a cause, they often had been dieting, because of changes in blood chemistry. Am I misinformed? — A.B.
ANSWER: You’re not misinformed. E.A. had fasted only for 36 hours. Glycogen (stored body sugar) is depleted quickly during a fast, and the body turns to fat for energy. Fat burning produces ketones, which can upset body chemistry. They can cause serious body perturbations.
A 36—hour fast would not be expected to kill anyone who wasn’t strenuously exercising. Death occurs in about a month of starvation and in four to 10 days of no fluid intake.
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. Readers may also order health newsletters from www.rbmamall.com.

Copy the Story Link