This presentation provides background science and health information related to the “Food and Fitness” unit created by scientists and educators at Baylor College of Medicine’s Center for Educational Outreach. The unit covers concepts related to energy, Calories, metabolism, diet and nutrition, and is particularly appropriate for students in grades 5–8. Viewing this presentation also fulfills part of the requirements for the Virtual Workshop on Energy, Food and Nutrition (“Food and Fitness”) offered for professional development contact hours on BioEd Online.

Funding for development of the Food and Fitness unit and accompanying online professional development was provided by the National Space Biomedical Research Institute (NSBRI), a consortium of leading biomedical research centers funded by the National Aeronautics and Space Administration (NASA). Visit the following sites for more information about these organizations:

Center for Educational Outreach, Baylor College of Medicine  http://www.ccitonline.org/ceo
National Space Biomedical Research Institute  http://www.nsbri.org
National Aeronautics and Space Administration http://www.nasa.gov

PowerPoint slides were written by Nancy Moreno to compliment Roberta Andings’ presentation on Adolescent Nutrition to a Food and Fitness Teacher Education Workshop in March, 2004.

The incidence of obesity among six- to eleven-year-olds in the US has more than doubled in the past 20 years (USDHHS, 2004). As reported by the Office of the Surgeon General (USDHHS, 2001), most young people are not following  recommendations set forth in the Dietary Guidelines for Americans. For example, 67%  of youths aged 6-19 exceed dietary guidelines for fat intake and 72%  exceed recommendations for saturated fat intake.

Most nutritional problems in adolescents are related to the consumption of too much “junk food,” or food with limited or no nutritional value. Most junk food is characterized by high levels of fats, particularly saturated fats, and refined sugar. The portion sizes of junk food also typically are very large. In addition, most adolescents eat very few fruits and vegetables per day or chose items, such as iceberg lettuce, with low nutritional values.

The eating habits of today’s adolescents will lead to future health care problems. Obesity is related to a number of health problems, including Type 2 Diabetes, heart disease, stroke and cancer (NHLBI, 2004). Osteoporosis also is a growing problem, even among adolescents. Poor nutrition and insufficient exercise both contribute to low bone density among teenagers.

Junk food is food with minimal nutritional value. Most junk food is characterized by high fat and sugar content, with few other nutrients. Examples of junk foods include sweetened soft drinks, fried foods, particularly French fries, chips and other snacks, and candy. Without guidance, most adolescents will not make healthy food choices.

Portion sizes of junk food have increased dramatically over the past 20 years. For example, when most fast food franchises originated, a “regular” serving of French fried potatoes contained 201 Calories. Today, a “supersized” serving of fries contains approximately 610 Calories (NHLBI, 2004). The packaging of many kinds of junk foods in bags or pouches makes it difficult for consumers to estimate and compare serving sizes.

Sugar-sweetened beverages are now the principal source of added sugars in the diets of Americans (Guthrie, 2000). High sugar drinks, including fruit juices, contribute large of amounts of calories to the diets of adolescents. Further, most people do not reduce their consumption of other foods to compensate for the high number of calories consumed as sweetened beverages.

Many Americans overestimate portion sizes. When teaching portion sizes, it can be helpful to have students estimate the number of servings of juice or other drinks contained in a typical drinking glass. Even though a serving of fruit juice typically is four ounces, most adolescents drink from glasses that contain between 10 and 16 ounces of liquid. Soft drinks are a major source of hidden added Calories in adolescents’ diets.

Restaurants often serve quantities of food that exceed a single portion size. For example, a typical “super-sized” meal can contain as many as 1,500 to 2,000 Calories—almost an entire day’s worth of Calories—in a single meal or snack. A sedentary lifestyle also contributes to obesity. In particular, television viewing has been linked to weight gains and obesity among young people. Researchers have hypothesized that television viewing contributes to obesity by displacing physical activity, increasing calorie consumption while watching (including the effects of advertising) and reducing resting metabolism (Robinson, 2001).

Food labels and other guides often use “serving size” to describe a recommended single portion of a food. Serving sizes are different for various kinds of food (liquid vs. solid, or cooked vs. raw). In general, adolescents tend to overestimate portion sizes. The “Nutrition Facts” labels on most foods provide important information about serving sizes and the number of servings contained within a single package. For example, even though most soft drink consumers drink an entire 12- or 16-ounce container at one time, most soft drink labels identify the contents as two or more servings.

Students need easy guidelines to help them estimate appropriate serving sizes of different kinds of foods. Some rules of thumb include the following.

Palm of hand or deck of cards = one serving of meat, fish or poultry.
Size of closed fist or a tennis ball = one serving (one cup) of rice, pasta, fruit or raw vegetables.
Cupped hand = one serving (one cup) of dry cereal.
Two fingers or a domino = one serving (one ounce) of cheese.
Tip of thumb = one serving (teaspoon) of butter or margarine.

Consumption of large food portions, combined with sedentary lifestyles, is linked to overweight and obesity in adolescents and adults.

Serving sizes on food labels are designed to make it easier to compare the calorie and nutritional content of similar products and to identify nutrients present in a food. At a minimum, food labels contain information about serving sizes; calories; calories from fat (dietitians generally recommend that no more than 30% of calories come from fat over the course of the day); percent daily values of major nutrients; total fat; saturated and trans fat (these unhealthy fats are listed under total fat—saturated fat and trans fat raise cholesterol and increase a person's risk for developing heart disease); unsaturated fats (liquid at room temperature, these are the healthy fats); cholesterol; sodium; total carbohydrates (which includes dietary fibers, sugars, and other carbohydrates); protein; vitamins A and C; calcium and iron.

Carbohydrates are the most abundant source of calories in most people’s diets. Carbohydrates are either simple (called sugars) or complex (called starches). Cereals, rice, potatoes, breads, pastas, fruits, and vegetables all contain high amounts of carbohydrates. Not all sugar in food is added. Lactose, or milk sugar, is a natural ingredient in milk. Fruit also has high amounts of naturally occurring sugar.

When reading a food label, it is important to pay attention to the number of servings contained within a package and the amount of saturated fat. Saturated fat contributes to heart disease—the number one killer of adults in the US. Most saturated fats are solid at room temperature. The words, "hydrogenated," "partially hydrogenated," or "shortening,” also are used to describe saturated fats.  With true “low-fat” foods, fewer than 30%  of the total calories come from fat.

Students are not always able to make optimal food choices. Thus, it is important to help them select healthier alternatives when confronted with several imperfect options in the school cafeteria or at a fast food restaurant. In other words, students can learn to make better “bad choices.” In general, it is advisable to drink water instead of sweetened soft drinks, reduce portion sizes, and avoid fried foods.

A dinner plate can be used to help students estimate appropriate amounts of foods. Approximately one half of the plate should contain fruits and vegetables. The other half should contain a protein source (fish, meat, poulty, beans) and a starch (potatoes, rice, bread).

Food lessons help students learn to sample and enjoy new foods. Try introducing a new fruit or vegetable in class each week. Students are more likely to try something new when it is introduced to the entire group.

During the past 20 years, there has been a dramatic increase in obesity in the United States. In 1985, only a few states were participating in the Behavioral Risk Factor Surveillance System (BRFSS) and providing obesity data. In 1990, 10 states were reporting obesity prevalence rates of less than 10 percent, 34 states were reporting obesity prevalence rates of 10-14 percent and no states reported rates at or above 15 percent. In 2005, 4 states have obesity prevalence rates of 15–19 percent; 29 states have rates of 20–24 percent; and 17 states report a rate of 25 percent or over.

Obesity is defined as having a very high amount of body fat in relation to lean body mass, or having a Body Mass Index (BMI) of 30 or higher.
BMI is a measure of an adult’s weight in relation to his or her height, specifically one’s weight in kilograms divided by the square of his or her height in meters. BMI can be calculated online at http://www.cdc.gov/nccdphp/dnpa/bmi/calc-bmi.htm

Teenagers and adults need to participate in at least 30 minutes of physical activity each day. Physical activity, however, does not have to consist of structured exercises. Any movement counts as physical activity. Teenagers who resist traditional forms of exercise, might not be aware that other activities, such as dancing or shopping, also contribute to fitness.

To help teenagers be more active, give each student an inexpensive pedometer and suggest that they try to log at least 10,000 steps per day. Or, have students pledge or sign a contract to march in place for at least 30 minutes each day while watching television.

Only 13.5 percent of girls and 36.3 percent of boys aged 12 to 19 in the United States get the recommended daily amount of calcium, placing them at serious risk for osteoporosis and other bone diseases. Nearly 90 percent of adult bone mass is established by the end of this age range. Dairy products are a good source of calcium, but after the age of two, children should drink skim milk instead of two percent or whole milk. Since some children find the taste or color of skim milk objectionable, try adding approximately 1/2 teaspoon of vanilla per quart of milk or adding a squirt of chocolate syrup. To improve the appearance of skim milk, add 1/4 cup of powdered skim milk to a gallon of milk.

As many as 40% of adolescents may be deficient in Vitamin D, a fat-soluble vitamin essential for calcium absorption. Calcium is necessary not only for the development and maintenance of healthy bones and teeth, but also for the functioning of the nervous system. Vitamin D also may have a role in preventing potentially cancerous growths in the colon. It is found in fortified milk, cheese, fish, oysters and fortified cereals. The body also can manufacture its own vitamin D, if the skin is exposed to sunlight. Ten to 15 minutes of sunshine three times weekly is adequate to produce the body's requirement of vitamin D (MedLine Plus, 2004). Many teenagers do not receive enough vitamin D, because they have reduced exposures to sunlight due to increased use of sunscreens and fewer outdoor activities.

Recent research suggests that weight reduction plans that include calcium from dairy sources (milk, yogurt, etc.) promote weight loss more effectively than plans without dairy calcium (Zemel and Miller, 2004). In addition, dairy calcium particularly appears to reduce abdominal fat.