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updated 4/15/2005 1:08:59 PM ET 2005-04-15T17:08:59

Most people aren't very good at estimating calories or what it takes to lose weight. For example, strict vegetarians tend to be leaner, studies suggest, but going meatless isn't always the best way to cut calories. How does a person assess their basic calories needs? And do "fat-burning" exercises really burn more calories? Registered dietician Karen Collins explains.

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Question:Are meatless meals a good way to cut calories?

Answer: They can be, but don’t assume that absence of meat automatically means lower calorie content.

A meatless meal that contains a lot of fat from foods that are deep-fried or cooked in a lot of butter or oil will not be low-calorie. Likewise, large amounts of high-fat cheese or concentrated sweets like syrup or sugar add significant calories regardless of whether a meal contains meat.

To reduce calorie content, make low-calorie foods such as vegetables a major focus of the meal. The effect of meat and poultry on calories varies dramatically from high-fat choices like sausage, regular ground beef, and chicken wings to low-fat choices like pork loin, beef sirloin, and skinless turkey or chicken breast meat.

Finally, one of the strongest influences of all on a meal’s calorie content is how much you eat. Overeating can turn any meal into a source of too many calories. The American Institute for Cancer Research (AICR) has an educational program called the New American Plate, which shows how the combination of what and how much we eat determine the impact of our eating on health and weight control.

Question: Why do different sources recommend different calorie levels for me?

Answer: Assessing someone’s calorie needs accurately is not a simple task. There are a variety of formulas that estimate people’s calorie needs, based on different kinds of personal data.

These formulas can yield answers that differ by several hundred calories. Generally, you will get more accurate results when a formula considers or includes more variables.

These include your height, weight, sex, age and as detailed and accurate an estimate of your physical activity as possible. Even when all these variables are factored in, however, the calculation is still only a best guess, because people are unique.

If you’re maintaining a healthy weight, you can conclude that your current calorie intake is right for you. If you need to lose weight and want a calorie limit to strive for, estimate your current intake as accurately as possible, and subtract 250 to 500 calories from that number. Try to eat no more calories than that amount each day.

Question: Will I lose more body fat with low-intensity or vigorous exercise?

Answer: Despite claims that manufacturers make for some exercise videos and workout equipment, describing low-intensity exercise as "fat-burning" exercise, if you have too much body fat, you've stored excess calories.

To lose that excess fat, you've got to burn more calories than you take in. Although a higher proportion of the calories you burn in low-intensity exercise (like walking) comes from fat, research clearly shows that in an equal period of time vigorous exercise (like running) burns so many more calories that it also burns more total fat.

However, vigorous exercise may not be the better choice for you. If you're out of shape, pushing yourself to workout vigorously will limit how long you exercise and, consequently, the number of calories you can burn. When exercise is painful or unenjoyable, it's also tough to make it a lifetime habit. And making physical activity a habit is important for long-term weight control and good health. In addition, pushing yourself too hard can risk your life.

If lower-intensity exercise is a comfortable match for you, just remember that the lower the intensity of your activity, the more time you will need to put in to burn that excess body fat.

As a guideline in developing your healthy lifestyle, the American Institute for Cancer Research recommends reaching for an hour a day of moderate exercise like brisk walking and an hour a week of vigorous exercise. These amounts will lower your cancer risk, boost your overall health and promote a healthy weight.

Nutrition Notes is provided by the American Institute for Cancer Research in Washington, D.C.

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