Provided by Saint Paul Pioneer Press on 9/21/2004

Depending on the diet du jour, you should eat more carbohydrates, less carbohydrates, more fat, less fat, more protein, less protein. Whatever the gimmick, these diets have one thing in common: calories.

Calories are a basic element of nutrition. A calorie is a unit of energy. One pound is equal to 3,500 calories. So, if you want to lose weight safely, try cutting back 500 calories a day. That will add up to a loss of about a pound a week.

We asked three experts for their help in demystifying calories. Based on questions they often get asked, here are 10 things about calories you need to know.

1. What is a calorie?

A calorie is a measure of energy. Everybody needs a certain amount of energy for daily activities. If you take in more calories than you burn, you will gain weight. If the calories you ingest are equal to the calories you expend, you will maintain your weight. If you take in fewer calories than you burn, you will lose weight.

"As simple as that is, losing weight and weight maintenance are not simple," says pediatric dietitian Karri Larson of Gillette Children's Specialty Healthcare in St. Paul.

2. Where do calories come from?

Calories come from three main sources: protein, carbohydrates and fat. One caveat: alcohol contains calories, but our bodies don't need them like they do protein, carbohydrates and fat, Larson says. At 9 calories per gram, fat packs a greater caloric wallop than protein or carbohydrates, which are 4 calories apiece. In other words, a gram of butter has about twice as many calories as a gram of apple or chicken. Water, vitamins and minerals do not have calories.

3. Do calories count?

Absolutely. But "people keep looking for the magic bullet," says Dr. Donald Hensrud, physician nutrition specialist at the Mayo Clinic. The bottom line: "No matter where they're from, calories count."

4. What factors influence a person's daily caloric needs?

They hinge on age, gender, body mass and activity level. Most women need 1,600 to 1,800 calories a day, while most men should aim for 2,200 calories, Larson says. Think consistency. "Certainly at holiday times, people eat more," she says. "That's OK, so long as people decrease their intake before and after."

5. Is there a safe level of calories on a diet?

People should not go below 1,600 calories a day without a doctor's order, says registered dietitian Carrie Peterson, an instructor at the University of Minnesota and nutrition consultant for the five pro sports teams in Minnesota. Diets that go substantially lower than that miss important nutrients.

Often, people forget the important role of movement in the caloric equation. That doesn't just mean a gym workout. "It's total physical activity throughout the day," Hensrud says. "You can burn a lot more calories through the day than through an exercise session. People underestimate that."

6. If a person eats late, will those calories get stored as fat?

This is a myth, Hensrud says. The problem with night eating is that people usually have less inhibition and may be more likely to indulge. They may also pick higher-fat, higher-calorie foods. It takes less energy for the body to convert fat than carbohydrates. "A calorie is a calorie is a calorie," Hensrud says.

7. Does volume equal calories?

People often assume that the amount of food is equivalent to the caloric content of the food. Not so, say researchers who study caloric density. For example, 1 1/3 sticks of butter has the same calories as 35 cups of green beans or 10-11 heads of lettuce. If you eat a diet that is lower in energy density, high in fruits and vegetables, you'll get full without a lot of calories, Hensrud says.

8. Does yo-yo dieting lower metabolic rate?

No. It's a myth that a person will have trouble losing weight the second third, fourth, fifth time around because they wrecked their metabolic rate, Hensrud says. Moreover, supplements that promote overnight success "lose weight while you sleep" are nonsense. "It's possible there might be a minor change, but for all practical purposes, it is a very small amount of calories and not clinically significant," Hensrud says.

9. As we age, do we need fewer calories?

Typically yes, though it depends on activity levels, Peterson says. As we age, we experience a decrease in lean body mass and increase in fat tissue. Since muscle is more metabolically active than fat tissue, it needs more calories to sustain itself.

10. Does "sugar-free" mean "calorie-free?"

Maybe in a fantasy world, but not on this planet. A sugar-free product is just that: a product without sugar, which is one type of carbohydrate. "It could still have starch, fat and protein," Larson says. "It still has calories."