The only way for your child to get rid of excess weight is to use more calories than he eats. If his calorie intake is above what his body requires for daily activity and physical growth, and he doesn't use that energy for exercise or other activity, those bonus calories have to go somewhere. His body will take that extra fuel and store it as fat. Conversely, if he cuts his daily calories (or keeps them steady) and increases activity levels, his body will turn to those fat stores for energy.

The rate of your child's metabolism will also impact how quickly, or slowly, he loses weight. In addition, hormonal changes (such as those that hit at puberty) also play a role. How many calories your child should take in is based on his age and gender. Table 5-1 below outlines the suggested daily caloric requirements for girls and boys by age as recommended by the U.S. Department of Agriculture (USDA).

As of the writing of this book (2004), the USDA's Center for Nutrition Policy and Promotion was in the process of developing a revised version of the USDA food pyramid. The information provided here on daily calorie requirements for children is based on the daily food intake patterns that the food pyramid uses as its foundation.

Because the new food pyramid will not be finalized until 2005 (after this book has gone to press), you'll find both the current and the proposed caloric standards below (Tables 5-1 and 5-2, respectively). The proposed energy requirements for daily food intake in the new food pyramid are based on the Institute of Medicine's Dietary Reference Intakes Report (2002).

Please note that any new information regarding the food pyramid that is included here is based on the proposed preliminary draft data from the USDA as of early May 2004 and does not reflect any changes made after the point. As such, the information provided here may turn out to be different from the final published release. Always consult with your child's doctor and/or her registered dietitian for the most current official dietary standards and how they apply to your child's particular health situation.

Table 5-1: Daily Energy (Calorie) Requirements (as of May 2004)

Age Range	Females	Males
1–3	1300	1300
4–6	1800	1800
7–10	2000	2000
11–14	2200	2500
15–18	2200	3000

Table 5-2: Daily Energy Requirements (projected, 2005)

Age range	Activity level	Females	Males
2–3	Sedentary	1000	1000
	Low active	1000–1200	1000–1400
	Active	1000–1400	1000–1400
4–8	Sedentary	1200	1400
	Low active	1400–1600	1400–1600
	Active	1400–1800	1600–2000
9–13	Sedentary	1600	1800
	Low active	1600–2000	1800–2200
	Active	1800–2200	2000–2600
14–18	Sedentary	1800	2200
	Low active	2000	1400–2800
	Active	2400	2800–3200

Sedentary indicates no regular exercise outside of the daily physical activities of living. Low active means regular exercise equivalent to walking 1.5 to 3 miles daily at a rate of approximately 3 to 4 miles per hour. Active is regular exercise equivalent to walking more than 3 miles daily at 3 to 4 miles per hour.

The 3500-Calorie Equation

Calories in food are actually measured in kilocalories — the amount of energy required to raise the temperature of one kilogram of water by exactly 1°C. Fats are high in calories, while proteins and carbohydrates are lower. (One gram of fat has nine calories, and proteins and carbohydrates have four calories per gram each.)

To lose one pound of body weight, your child needs to burn 3,500 calories more than he consumes. That goal is best reached through a combination of dietary and exercise adjustments. A fitness diary that tracks diet and activity can help you determine if he's eating more calories than required for his age. Just adding a brisk one-hour family walk to your child's routine can burn an extra 440 calories daily and could potentially add up to a total weight loss of six pounds per year without any adjustments in calorie intake.

Remember that the best types of calories to cut back on are those that are low in nutrients. Chips, soda, candy, anything deep-fried — it isn't hard to find suitable targets for elimination in the modern American diet.

Metabolism

Metabolism refers to the chemical and cellular changes within the body that are associated with both generating and utilizing energy. When a substance introduced into the body (such as food or medicine) is metabolized, it is broken apart and processed for use in physical functions and growth.

The human body needs a minimal number of calories just to perform the basic functions of living (for instance, breathing, pumping blood, maintaining the central nervous system functioning, and staying warm) throughout the day. That number is called the basal metabolic rate, or BMR (also known as resting energy expenditure, or REE). Up to 70 percent of the energy your child requires daily is for these basic needs.

Severely overweight children actually have a higher BMR than normal-weight children because their body mass is larger, and as a result they require more energy to fuel organ systems and basic bodily functions. Table 5-3 below provides the simple formulas for calculating BMR.

Table 5-3: Basal Metabolic Rate (BMR)

Age range	Female	Male
0–3	(61.0 × weight) — 51	(60.9 × weight) — 54
3–10	(22.5 × weight) + 499	(22.7 × weight) + 495
10–18	(12.2 × weight) + 746	(17.5 × weight) + 651

Weight is in kilograms; one kilogram is equivalent to 2.2 pounds.

Source: The Commission on Life Sciences of the National Academy of Sciences, Recommended Daily Allowances (1989).

The BMR can help you determine the bare minimum number of calories required to sustain a sleeping or completely still child. But since no child sits still for very long, you also need to know your child's active metabolic rate (or AMR). This is the caloric requirement for a day's worth of all physical activity (including everything from getting dressed to running a marathon). Very active children may burn up to twice as many calories as their BMR.

Exercise naturally boosts your child's metabolism by calling on stored calories for fuel. The metabolic lift of physical exercise also continues up to an hour after the activity has ended. The other metabolic plus of exercise is that it builds muscle tissue. Muscle tissue needs more “fuel” to function — even when your child is at rest. Fat, on the other hand, isn't as active. By adding lean muscle mass to his body, your child will make use of calories much more readily.

Any calorie reduction in your child's diet should be incremental and moderate. When you dramatically cut calories, the body's natural reaction is to slow metabolism to conserve energy. It goes into a pseudo-starvation mode and stockpiles those calories in the form of fat for later use. In addition, your child's developing body may lose access to important nutrients. While some temporary weight loss may be achieved, the sense of deprivation your child experiences will not build the kind of life-long weight maintenance skills you want to encourage.

Metabolism is also impacted by weight gain. As body fat increases, your child's metabolism will slow to achieve what is called a “set point” or new (and higher) level of calorie/energy balance. The best way to keep your child's metabolism humming along efficiently is to encourage small and frequent meals, instead of one or two daily feasts.

This way, the body will burn caloric energy as it is taken in throughout the day rather than getting it all at once and having to store the excess fuel in fat. Your child's metabolic rate will actually increase temporarily after eating as her body digests the food. Approximately 5 to 10 percent of the calories in the meal itself are burned during digestion/metabolism.

There are some endocrine disorders, such as Cushing's disease, that can impact metabolism and can cause excessive weight gain.

Hunger and Appetite

The appetite center of your brain is located in the hypothalamus. The lateral hypothalamus controls appetite signals, and the ventromedial hypothalamus controls satiety, or feelings of fullness. The hypothalamus is the master switch of the endocrine system, the hormone-secreting organs and glands that regulate such body functions as metabolism, growth, sexual development, and hunger.

Feelings of hunger and satiety are actually controlled by a self-regulating feedback loop that detects hormone levels in the bloodstream and secretes hormones in response. A complex series of biochemical processes mediate the relationship between hunger, metabolism, and weight in the brain. One enzyme (the AMP-activated protein kinase, or AMPK) helps “turn on” appetite. AMPK is activated when there isn't enough glucose energy present in the cells.

The hormone leptin also operates on the hypothalamus, but with the opposite effect, suppressing appetite. However, studies indicate that people who are overweight or obese become resistant to leptin. PYY is another appetite-suppressant hormone that has been shown in human trials to reduce appetite by up to 30 percent. It appears not to cause resistance in the overweight as leptin does.