Are You at Risk for Chronic Disease

The more of these risk factors you have, the more likely you are to benefit from weight loss if you're overweight or obese.

  • Do you have a personal or family history of heart disease?
  • Are you a male older than forty-five years or a post-menopausal female?
  • Do you smoke cigarettes?
  • Do you have a sedentary lifestyle?
  • Has your doctor told you that you have:
  • High blood pressure?
  • Abnormal blood lipids (high LDL cholesterol, low HDL cholesterol, high triglycerides?)
  • Diabetes?

Source: U.S. Department of Agriculture and U.S. Department of Health and Human Services.

For more about these risk factors, see chapter 22, "Smart Eating to Prevent and Manage Disease."

more to go faster and farther. Some bodies—and some cars—are more fuel-efficient than others. That is, they use less energy to do the same amount of work. Age, size, shape, gender, physical condition, and even the type of "fuel" affect fuel efficiency. "How Does Your Body Use Energy?" on page 26 shows the proportion of energy used for each role in your body.

Your Basic Energy Needs

Energy for basal metabolism (basic needs) is energy your body burns on "idle." In scientific terms, basal metabolic rate (BMR) is the energy level that keeps involuntary body processes going: pumping your heart, breathing, generating body heat, perspiring, transmitting brain messages, and producing thousands of body chemicals. For most people, basal metabolism represents about 60 percent of their energy needs!

The simple "rule of ten" offers a quick, easy estimate of how much energy your body uses for basal metabolism daily. Figure on 10 calories per pound of body weight for women, and 11 calories per pound for men, to meet routine energy demands. Here's an example:

Consider an active 130-pound female. She would burn about 1,300 calories (130 pounds x 10 calories per pound) per day for basal metabolism and about 2,200 calories total per day. (That's 60 percent of total calories for her basic energy needs.) Now calculate for yourself: about how much energy might your body require for your basic needs?

Why can one person consume more calories day after day and never gain a pound? For another person of the same age, height, and activity level, weight control is a constant challenge. The "rule of ten (or eleven)" doesn't allow for individual differences in basal metabolic rate (BMR). Age, gender, genetics, and body composition and size, among other factors, affect basic energy needs. Although you don't need to know your BMR to achieve and maintain a healthy weight, that may be useful information for some people, perhaps athletes in training. Health or fitness professionals can determine that for you. Worth noting: A handheld palm device is available that individuals can use to measure their metabolic rate at rest.

Age Factor. Young people—from infancy through adolescence—need more calories per pound than adults do for growing bone, muscle, and other tissues. During infancy, energy needs are higher per pound of body weight than at any other time in life. And just watch a growing teenager eat; you know that energy needs are high during adolescence! (The "rule of ten" isn't meant for kids—especially not infants.)

By adulthood, food energy (calorie) needs—and BMR—start to decline: 2 percent for each decade. For

How Does Your Body Use Energy?

If you're like most people, here's how your body uses

the energy it "burns" each day:

Basic energy needs

(basal metabolism)

60%

Physical activity

30%

Digestion of food and

absorption of nutrients

10%

Total energy use for the day

100%

example, a woman who needs about 2,200 calories per day for her total energy needs at age twenty-five might need 2 percent less, or 2,156 calories per day, at age thirty-five. She may need another 2 percent less by age forty-five, and so on.

Why the decline in BMR? Body composition and hormones change with age. And with less physical activity, muscle mass decreases; body fat takes its place. Because body fat burns less energy than muscle, fewer calories are needed to maintain body weight, and the basal metabolic rate goes down. (As an aside, regular physical activity can help keep your metabolic rate up.)

If you continue to follow your teenage eating habits—and live a less active lifestyle—the extra pounds that creep on with age should come as no surprise! Unused calories get stored as body fat.

Family Matters. Genetic makeup and inherited body build account for some differences in basal metabolic rate—differences you can't change! (Families tend to pass on food habits to one another, too, which also may account for similarities in body weight.)

Body Size, Shape, and Composition. Consider the impact on BMR and energy needs:

  • A heavy, full-size car usually burns more fuel per mile than a small, sleek sports car. Likewise, the more you weigh, the more calories you burn. Body size makes a difference. It takes somewhat more effort to move if you weigh 170 pounds compared to 120. That's one reason why men, who often weigh more, use more calories than women.
  • A lean, muscular body has a higher metabolic rate than a softly rounded body with more fat tissue. Why? Ounce for ounce, muscle burns more energy than body fat does. So the higher your proportion of muscle to fat, the more calories you need to maintain your weight. A softly rounded body type has a greater tendency to store body fat then a lean, muscular body.

Tip: Stay physically active to maintain your muscle mass—and give your BMR a boost.

• A tall, thin body also has more surface area than a short body, and as a result, more heat loss; the net result—more calories burned (higher BMR) to maintain normal body temperature.

Gender Gap. The ratio of muscle to fat differs with gender, accounting for differences in basal metabolic rate. Up to age ten or so, energy needs for boys and girls are about the same, but then puberty triggers change. When boys start developing more muscle, they need more calories; their added height and size demand more energy, too.

By adulthood, men usually have less body fat and 10 to 20 percent more muscle than women of the same age and weight. That's one reason why men's basic energy needs are higher. In contrast, women's bodies naturally keep body fat stores in reserve for pregnancy and breast-feeding when a woman's energy needs go up. Refer to chapter 17.

Hot—or Cold? Outside temperature affects internal energy production. On chilly days, your BMR "burns" a little higher to keep you warm during prolonged exposure to cold. Shivering and moving to keep warm use energy, too. And in hot temperatures, your body's air conditioning system burns a bit more energy—for example, as you perspire to cool down.

The Diet Factor. Do you think that skipping meals or following a very-low-calorie eating plan offers a weight-loss edge? Think again. Severe calorie restriction actually can make your body more energy efficient and cause the rate at which your body burns energy from food to slow down! Your body then requires fewer calories to perform the same body processes. This slowdown in metabolic rate is your body's strategy for survival.

Physical Activity: An Energy Burner

Movement of any kind—a blink of your eye, a wave of your hand, or a jog around the block—uses energy. In fact, about 30 percent of your body's energy intake is used to power physical activity! At best, that estimate is imprecise because activity levels differ so much. Very active people need more calories, about 40 percent of their total energy for physical activity.

Common sense says that some physical activities burn more energy than others. The amount of energy used to power physical activity actually depends on three things: the type of activity, its intensity, and how long you do it. Suppose you walk with a friend of the same age and body size. The one who pumps his or her arms and takes an extra lap around the block burns more energy. The chart"Burning Calories with Activity" on page 28 shows how much energy (calories) get used for common, nonstop activities.

The Food Connection

Eating itself actually burns calories. Digesting food and absorbing nutrients use about 10 percent of your day's energy expenditure—about 200 calories if you consume 2,000 calories daily. But don't count on these processes to burn up all the energy in anything you eat!

Calorie Myths

Over the years, calorie myths of all kinds have developed. Do these unfounded notions sound familiar?

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