Health Mailbox

Q: I am wondering if the value of calories eaten equals the value of calories that are exercised off. If I eat 2,000 calories a day and do exercises worth 800 calories, is this the same as eating 1,200 calories and doing no exercise?

A: Not quite. In theory, a calorie eaten should be the same as a calorie exercised, but the math doesn't really work that way.

When a person starts exercising, all kinds of compensatory mechanisms kick in to defend body weight and hold on to as many calories as possible. From an evolutionary standpoint, our bodies were designed to maintain weight when food was scarce and gain weight when food is abundant.

HEALTH JOURNAL Health Journal: New Research Lends Weight to Effect of Low-Carb Diet -- in the Short Term You can e-mail Tara Parker-Pope at healthjournal@wsj.com.

So the natural tendency is to increase eating to make up for calories lost to exercise. If you have the willpower to resist those hunger pangs, the body still finds way to conserve calories.

You may get up a little slower in the morning or slouch a little longer in your chair -- burning a few less calories here and there to make up for calories lost through exercises. And once you start exercising, your body will become more efficient. The mile you ran last week that burned off 100 calories may burn off only 90 calories the following week.

From a practical standpoint it takes an enormous amount of exercise to burn a meaningful number of calories -- and very little food to erase it. It would take six days of walking 30 minutes a day to burn the 800 calories in your question. And even if you do manage to burn off 300 calories after 45 intense minutes on the treadmill, it just takes one cookie or two apples to erase those lost calories. Indeed, numerous studies have shown that exercise alone doesn't help people -- women in particular -- lose weight.

Exercise alone is "not a strong enough intervention in the face of other choices folks can make," says Joseph E. Donnelly, director of the center for physical activity and weight management at University of Kansas in Lawrence.

This doesn't mean you shouldn't exercise. It just means that cutting calories is the only practical way to lose weight. You should exercise because it will help you live longer and thwart heart disease and numerous other ailments. And exercise helps your diet work by preventing weight regain over time.

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Q: Regarding your article on Medicare's new drug program. How much of a penalty do you end up paying if you don't immediately subscribe to Medicare's new drug program in 2006?

A: Enrollment for the Medicare drug benefit begins Nov. 15, 2005, and continues through May 15, 2006. However, just as with other parts of Medicare, there is a late-enrollment penalty for eligible seniors who don't sign up right away. The penalties are a way to motivate healthy people to start paying, so the system is supported by a mix of healthy people who don't use its services and unhealthy people who do.

For every month an eligible senior delays enrollment for the drug benefit, he or she will pay a 1% higher premium for life, says Tricia Neuman, vice president of the health-care think tank Kaiser Family Foundation. Premiums start at roughly $35 a month, so those with drug bills of less than the $420 annual cost have to decide whether they want to pay for a service they likely won't use for a while. But if their drug costs skyrocket and they want to sign up two years later, their premiums will be 24% higher for the rest of their lives. The choice depends essentially on your own health history and your tolerance for risk.

Based on estimates of future rates, a person who signs up right away will pay $492 in premiums in the year 2008. But a person who waits two years to sign up will pay $610, and will continue to pay the 24% higher rate every year for life.

However, there's no penalty for seniors who decide not to get the new Medicare drug-discount card, which is being offered right now. Whether you get the card or not, you are still eligible for the 2006 drug benefit at regular rates.

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Q: In a past article, you described two back braces that can help relieve back pain. I'm afraid my general practitioner won't know how to get me one or if I would benefit. Do I have to consult an orthopedist?

A: You can find more information about the Disc Unloader at www.corflex.com and the Orthotrac Pneumatic Vest at www.treatmyback.com. These are medical devices and may not be suitable for everyone, so they should be prescribed by a doctor. Only Orthotrac requires a prescription for its custom-fitted vest, but your insurance company likely will insist on a prescription before reimbursing you. An orthopedic or sports-medicine specialist will be most familiar with the products, but the braces are available to any medical specialty. Your doctor can either contact the company to order the device for you or you can fax a doctor's prescription yourself.