DEAR DR. DONOHUE: I need help. I’m not winning the battle of the bulge. I don’t know why. I exercise and eat well. If you can think of anything that might help me, please tell me. – K.C.

ANSWER: People don’t gain weight unless they put more calories in their mouth than they use throughout the day. You have to know exactly how many calories you eat. Keep a careful record of the kinds and amounts of food you eat every day for one week. Get yourself a little calorie counter, and add them up. Then figure out the daily average. If you cut back 500 calories a day, you will lose 1 pound a week.

Increasing the amount of exercise will, of course, burn more calories. However, it’s hard to lose substantial amounts of weight through exercise alone. You have to combine exercise with calorie restriction.

I admit there are people who watch what they eat, exercise and still can’t lose weight. I can’t give you the reason why this happens. They must have a metabolism that differs from the average person’s.

I have never recommended what I am about to recommend to you – diet pills. They have had a checkered past. You recall the fen-phen craze? It was a diet pill taken by a large number of people. It had to be taken off the market because it led to heart valve problems. Many diet pills have had a similar history.

If a person makes an honest effort to cut back on eating and to increase exercise and still sees no results, then diet pills have a role in that person’s efforts to lose weight. Meridia, on the market since 1997, curbs appetite. Xenical has been around for six years. It contributes to weight loss by inhibiting fat absorption. Both require a prescription.

Drugs for weight loss are neither the sole nor the first answer. They might have a role as an adjunct to diet and exercise for people like you.

DEAR DR. DONOHUE: I have a problem retaining potassium. I take chlorthalidone for high blood pressure. I had to go to an urgent-care center recently because I was feeling so bad. They tested my potassium and found it to be 3. I am now on a potassium pill, but my potassium reading will be normal one day and low the next. I was very active before all this happened. Now my legs are weak, my stomach is bad, and my bowel movements have changed. I feel I have no life. What can I do? – M.J.

ANSWER: The normal blood potassium is 3.5 to 5.0. Low potassium usually doesn’t cause symptoms until it dips below 3.0. A very low potassium level makes a person fatigued, can cause muscle weakness, can lead to changes on the EKG, can give rise to dangerous heartbeats and can even bring on muscle paralysis. That last is extremely rare, and the potassium must be extremely low.

Top on the list of causes for low potassium is diuretics – water pills, like your chlorthalidone. Your doctor might suggest reducing the amount you take or tell you to switch to a water pill that doesn’t deplete body potassium. Dyazide and Midamor are two examples.

Foods high in potassium include baked potatoes with skin, sweet potatoes, orange juice, bananas, spinach and skim milk. It’s hard to restore potassium with foods alone. Potassium pills are needed. But potassium-rich foods can help maintain normal blood levels.

I don’t understand why your potassium is not normal now that you take a potassium supplement. You might have something else going on. Tumors of the adrenal gland can lower blood potassium levels. It’s time to look for these less-common causes of potassium depletion.

Readers interested in more information on potassium and sodium can order the booklet on those two minerals by writing: Dr. Donohue — No. 202, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6.75 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

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.