The Diet Detective: Nutrition and fitness questions answered

Although it's difficult to answer the thousands of questions we receive each year, here are the answers to a few of the most pressing.


Q. Do you burn fewer calories if you do the same exercise over and over again?

A. "Rarely," says William Haskell, Ph.D., deputy director of Stanford Prevention Research Center at Stanford School of Medicine.

"For most activities, if a person performs them regularly at the same intensity [e.g. speed] and for the same duration, and the person's weight remains constant, energy expenditure will not change significantly over time.

However, energy expenditure could decrease if the person's skill [mechanical efficiency] increases significantly, which in most situations does not occur." One of the few instances where it does happen is with beginning swimmers who become more efficient over time and therefore burn fewer calories during the same exercise session, explains Haskell.

Q. Is couscous one of the better whole grains?

A. No. It's actually a refined (not whole) grain, made from coarsely ground semolina pasta, and even though it's often seen as a healthier alternative to rice, it's really no different. (Look for whole-grain couscous.) Other grains, such as ryes and pumpernickels, are also typically made from refined flour.

Know your whole grains: According to the Whole Grains Council, examples of generally accepted whole-grain foods and flours are amaranth, barley (lightly pearled), brown and colored rice, buckwheat, bulgur, corn and whole cornmeal, farro, grano (lightly pearled wheat), Kamut, millet, oatmeal and whole oats, popcorn, quinoa, sorghum, spelt, whole rye, whole or cracked wheat, wheat berries and wild rice.

Q. It is more nutritious to eat fresh fruits and vegetables than frozen or canned?

A. No. Frozen and canned fruits and vegetables can be just as nutritious as fresh. They're often packaged immediately after picking, and this helps preserve most of the nutrients.

Canned produce does have a downside -- the vegetables can be high in sodium, and the fruits packed in sugary syrups. Look for low-sodium vegetables and fruits packed in water or juice.

Q. Can caffeine be lethal?

A. A caffeine overdose, while undoubtedly unpleasant, is extremely unlikely to be fatal. It's possible, but the chances of death are slim. According to Terry D. Blumenthal, Ph.D., a professor of psychology at Wake Forest University, Winston-Salem, N.C., "You would have to ingest more than 30 cups of coffee in one sitting. It is, however, possible to swallow enough caffeine pills to cause fatal convulsions and respiratory failure."

Much more likely than a fatal reaction, however, a caffeine overdose can produce two sets of symptoms, depending on the nature of the overdose. An acute overdose, reached by quick ingestion of an extreme amount of caffeine, can result in tremors, restlessness, nausea, vomiting, increased heart rate and confusion. Serious intoxication may cause delirium, seizures, irregular heart rate, hypokalemia (low potassium levels) or low blood sugar.

In the case of chronic high-dose caffeine intake, one can experience nervousness, irritability, anxiety, shaking or muscle twitching, insomnia, palpitations and hyperreflexia (overactive reflexes).

Q. True or false: If you have an appetite, it means you're hungry.

A. False. According to Richard D. Mattes, M.P.H., Ph.D., R.D., professor of nutrition at Purdue University, "Appetite refers to food-seeking behavior that guides consumption." It does not, however, predict how much you eat.

Appetite and food intake don't correlate, in part because the definition of appetite is so broad. It includes all the impulses and instincts that guide our relationship to food. So, depending on how much we crave, our level of hunger, our tendency to indulge or deny cravings, and the amount of food it takes before we reach satiety, the amount we actually consume can differ greatly from person to person, even if the hunger level is similar.

"In fact, it's possible to be hungry without having an appetite, although this usually occurs only when someone is sick, or perhaps depressed or very stressed. The body sends signals that food is needed -- hunger -- but due to one of these states food might be unappealing, and consequently there's no appetite," says Hollie Raynor, Ph.D. R.D., assistant professor of psychiatry and human behavior at Brown Medical School.

Q. True or false: Buttermilk is the most fattening of all milk.

A. False. It certainly sounds like it would be, but it's not. In fact, buttermilk is usually made from skim milk, so it's actually lower in calories than whole milk, at 100 calories per cup compared with 150 in whole milk.

Buttermilk is also low in cholesterol and fat. At one time, buttermilk was what was left after the butter had been churned from cream. So it was a way of using up the "leftovers," in the interest of conservation. Now, however, it is fermented (with cultures) from skim milk.

Q. Are there any differences between Pilates and yoga?

A. Yes. Pilates and yoga are often compared because they both integrate mind and body and strengthen core muscle groups. However, according to Brooke Siler, a New York City Pilates instructor and author of Your Ultimate Pilates Body Challenge (Broadway, 2005), "Pilates is a system of exercise utilizing the body itself along with specifically designed apparatus as resistance tools to stretch, strengthen and tone.

Unlike yoga, Pilates doesn't segregate body parts or focus on tranquil, meditative poses. Pilates is an athletic, dynamic and core-focused system requiring concentration and precision to improve strength, flexibility, cardiovascular capacity and coordination."

When it comes to yoga, in addition to the thousands of asanas or poses, a lot of other things are going on. "Yoga is a practice that integrates the whole person; it not only provides a challenging workout, but also releases mental stress and tension and creates a feeling of emotional stability," says Baron Baptiste, a power-yoga expert and author of My Daddy is a Pretzel (Barefoot Books, October 2004).

Yoga also has incorporated into its core a 5,000-year-old tradition, and it's part of a more complicated, larger physical, philosophical and spiritual practice -- making yoga much broader, offers Dayna Macy, communications director of the Yoga Journal.

However, according to Mieke Scripps, M.P.T., D.P.T., an orthopedic physical therapist for the Miami City Ballet, "Pilates and yoga are both great forms of exercise because they encourage the use of muscles that we don't use in daily life activities or typical forms of exercise such as running, biking, weight lifting and aerobics.

Injuries often occur from poor postural habits and muscular imbalance. Yoga and Pilates help correct these muscular imbalances for overall body health. Either form of exercise can be beneficial when taught by a qualified instructor who gives individualized attention to each student."

Q. Should you warm up or stretch before or after a workout?

A. According to Michelle Olson, Ph.D., a professor of exercise science at Auburn University in Montgomery, Ala., many studies have demonstrated that stretching before exercise doesn't prevent injuries.

Not only that, but Olson warns that "static stretching can decrease performance because it decreases the ability of the muscles to put out as much power as they normally would for up to one hour." Olson believes that stretching after you exercise is best because, "Your muscles have more blood flow at that time and less friction force."

She does, however, recommend doing a warm up. Basically, this should consist of doing an activity very similar to the one you're about to do, but slower and at a lower intensity that builds over a 10- to 15-minute period.

In fact, a recent study appearing in Medicine & Science in Sports & Exercise demonstrated that during certain endurance exercises lasting four to five minutes, performance is actually enhanced by a warm up regardless of the warm up's intensity.

Charles Stuart Platkin is a nutrition and public health advocate, author of the best seller Breaking the Pattern (Plume, 2005), Breaking the FAT Pattern (Plume, 2006) and Lighten Up (Penguin USA/Razorbill, 2006) and founder of Integrated Wellness Solutions. Sign up for The Diet Detective newsletter free at

Copyright 2006 by Charles Stuart Platkin

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