Q. Diet or exercise: Which is better to help you lose weight?

A. According to the Pew Research Center, about a third (34 percent) of Americans are neither exercising nor dieting; 17 percent are doing both; 8 percent are dieting but not exercising; and 40 percent are exercising but not dieting. So, who is right? Well, a recent study in the Journal of Clinical Endocrinology & Metabolism demonstrated that dieting and exercise are equally good at taking off the pounds — as long as the number of calories consumed is the same as the number of calories burned.

And, according to Dr. David L. Katz, associate professor of public health and director of the Prevention Research Center at Yale University School of Medicine, the answer is simpler than the debate would imply.

"It depends," he says. "If you can exercise enough to burn more calories and would rather do that than cut calories, then exercise is the way to go. If, however, you're more willing to trim your portions than go out running, dieting will work better." Think about which you would rather do: skip the mayo on your burger, or walk it off for 35 minutes?

That said, it's clear from the research that most people who have lost weight and kept it off for five years or longer combine diet and exercise. In fact, "It's nearly impossible to exercise enough to control weight without attention to diet," adds Katz. And, conversely, it's nearly impossible to sustain weight-loss without some increase in physical activity. In addition, an increase in physical activity offers other benefits, including cardiovascular health, and strength training can add muscle, which can burn extra calories at rest (each pound of muscle added will increase the calories your body burns by about 30 to 50).

Q. Should you eat three or six meals per day?

A. It depends on whether those six meals are going to increase or decrease how many calories you take in for the day overall. According to Milton Stokes, spokesperson for the American Dietetic Association, "A small amount of research says that eating mini-meals consisting of less food more frequently may help rev metabolism and prevent extreme variations in blood sugar. At the very least you should eat three times daily. Some people reap benefits from eating about every four or five hours daily. That isn't, however, a license for going hog wild all day."

People get hungry every four hours, says Nancy Clark, a sports nutritionist and author of Nancy Clark's Sports Nutrition Guidebook (Human Kinetics, 2003). She recommends four meals: breakfast, two lunches with about three hours between them, and dinner. She believes the two lunches will lessen your appetite at dinner and solve the energy problem that most people have. Her motto: "Fuel by day, diet by night."

Katz favors six meals because, "People trying to control their weight are often worried about deprivation and going hungry. Having food available at regular intervals cuts off this anxiety," he says.

"I caution people about the six meals per day," says Lona Sandon, a professor of nutrition at the University of Texas Southwestern Medical Center at Dallas. "There is nothing magical about six meals per day, and any opportunity you give yourself to eat is an opportunity to overeat. Six meals a day at 300 calories each would be a total of 1,800 calories for the day. A bowl of cereal with skim milk and maybe 1/2 cup of juice would be about 300 calories. People who follow this type of plan need to really watch their portion sizes."

Katz agrees. He believes that if you are eating often, you must make sure you're eating well. You have to be even more vigilant.

Q. Which is better for you — walking for 15 minutes each day or going on an all-day hike on the weekend?

It's pretty much unanimous among health experts: The daily walk, even for a few minutes, is better than the all-day weekend hike. According to Stephen Rice, a sports-medical expert at the Jersey Shore Medical Center in Neptune, N.J., "Daily exercise is superior to being a 'weekend warrior.' Couch potatoes Monday through Friday and vigorous athletes Saturday and Sunday can come up with both acute and overuse injuries easily."

Not only that, but if you have the time to walk 15 minutes a day, it is better for your health and fitness, and, according to Michael R. Bracko, a spokesman for the American College of Sports Medicine, these short walks can be the start of bigger and better things for fitness and health and could ultimately change your life.

Charles Stuart Platkin is a nutrition and public-health advocate, and author of "Breaking the FAT Pattern" (Plume, 2006). Sign up for the free Diet Detective newsletter at www.dietdetective.com.