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Web Review - Chapter 16 – pg. 1 Concepts of Fitness and Wellness / Concepts of Physical Fitness Web Review - Concept 16 Nutrition Web Review is an internet-based supplement that is available for use with Concepts of Fitness and Wellness: A Comprehensive Lifestyle Approach (4th edition) and Concepts of Physical Fitness: Active Lifestyles for Wellness (11e). Click on a topic at left to begin exploring the content in this chapter. If you know the WebReview number or page number of the web icon in the text you can click on the direct link you are looking for. The material available here is for the exclusive use of students and instructors using the Concepts-based approach. All rights reserved (McGraw Hill Higher Education) Return to the Concepts of Fitness and Wellness Resource Page Return to the Concepts of Physical Fitness Resource Page Concepts of Fitness and Wellness / Concepts of Physical Fitness Web Review - Chapter 16 – pg. 2 Web16-1: Understanding Differences in Nutritional Guidelines (p. 308) The government uses a variety of different nutritional guidelines to provide recommendations to the public. Many people use these guidelines interchangeably but there are some differences in the intent and scope in some of the guidelines. A brief description of each of the guidelines is provided below. RDA: The National Research Council's Recommended Dietary Allowances (RDA) is the standard for the daily nutritional needs of healthy people. Broken down by gender and age, it covers 25 vitamins, minerals, and trace elements that are critical for a healthy diet. RDA's are neither the absolute minimum, maximum, or ideal amount of a nutrient you should consume; they merely provide an amount that you can be sure is safe and will promote proper health and development. The RDA’s are set by the Food, and Nutritional Board of the National Academy of Sciences/National Research Council. U.S. RDA: The FDA established the U.S. Recommended Daily Allowance (USRDA) in 1973 as a simplified daily nutritional requirement standard for food labeling. Because of confusion between the terms USRDA and RDA, the term USRDA has been renamed RDI. RDI: The FDA established the Reference Daily Intake (RDI) to replace the term USRDA (see above) due to confusion between the terms USRDA and RDA. The RDA also adds six new nutrients, Vitamin K, Selenium, Chloride, Manganese, Chromium, and Molybdenum. DRV: The Daily Recommended Values (DRV) are established for special components of foods not listed by the RDI's, such as Fat, Cholesterol, Carbohydrates, and Protein. Unlike other daily nutritional requirements, the DRV's are derived from how many calories a day you need. Web Review - Chapter 16 – pg. 3 Concepts of Fitness and Wellness / Concepts of Physical Fitness Web16-2: Estimating Energy Expenditure (p. 311) Daily energy expenditure is made up of the basal energy requirements that are needed for daily living as well as the amount of energy expended during physical activity. An additional component, known as the thermic effect of food, reflects the energy required for the processing and metabolism of food. This component is thought to comprise about 10% of a person’s daily energy expenditure. There are various methods that are available to assess energy expenditure. Self-report instruments are the most commonly used since they can be conducted on large numbers of people in a cost effective manner. The self-report instrument used in lab 15-C requires an individual to keep a fairly detailed log over the course of the day. This provides a fairly precise measure of energy expenditure. It is also possible to assess energy expenditure more crudely with other self-report procedures. One simple procedure is to estimate basal metabolic rate and add on an estimate of calories expended in physical activity. Follow the steps below to estimate your daily energy expenditure. Step 1: BMR (kcal) = 10 x ______ Wt. (lbs) = _____ kcal Step 2: PA (kcal) = ______ BMR(step 1) x _______ PA level * = _____ kcal = _____ kcal Estimate your activity level and use the following values in the calculation: Inactive = .30 Moderately active = .50 Vigorously active = .80 Step 3: Total EE (kcal) = ___________ BMR (step 1) + _________ PA (step 2) This calculation can provide only a rough approximation of a person’s energy expenditure. Basal metabolic rate (step 1) will depend largely on body size since larger people will require more energy at rest. The contribution from physical activity will vary by a person’s activity status. This is expressed here as a multiple of a person’s BMR since larger people will expend more calories for a given level of physical activity. The sum of these two effects provides an estimate of energy expenditure. The results can only reflect a “typical” energy expenditure value as your activity level is likely to vary considerably from day to day. Web Review - Chapter 16 – pg. 4 Concepts of Fitness and Wellness / Concepts of Physical Fitness Web16-3: A Comparison of Dietary Fats (p. 311) Fat is one of the three main nutrients that supply energy to the body. The other two are carbohydrates, and proteins. Fats are made up of hydrocarbon chains (chains of carbon and hydrogen) of varying lengths. Fats vary in the exact arrangement of carbon and hydrogen on the molecule and in the overall length of the chain. A fat is considered saturated if all of the available carbon molecules have hydrogen on them. This chemical structure causes saturated fats to be solids at room temperature. Saturated fat comes mainly from animal sources, like meat, butter, and milk. A fat is considered unsaturated if it has one (mono-) or more (poly-) carboncarbon “double bonds”. This double bond changes the chemical properties and causes these fats to be liquids at room temperature. Unsaturated fats are typically from vegetable sources and inlclude the fats found in corn, safflower, soybean, and sunflower oils, for example. There is also the type of fat (Omega-3 fatty acids) found in many higher-fat seafoods such as mackerel, and salmon. The chemical structures of a saturated and unsaturated fat are presented below for comparison. H HHHH H HHHH H HHHH0 HC- C- C-C-C-C-C-C-C-C- C-C-C-C-C-C-OH H HHHH HHHHH H HHHH Palmitic Acid - a saturated fat H HHHH H HH HH H HHHH 0 HC-C- C-C-C-C-C-C-C= C-C-C--C-C-C-C-C-C-OH H HHHH HHHH H HH H HHHH Oleic Acid - an unsaturated fat While the two compounds look very similar, the chemical properties and metabolic effects of these fats are very different. Saturated fats are known to be atherogenic, meaning they have a tendency to promote atherosclerosis (the buildup of fatty plaque on the walls of the arteries). Unsaturated fats, on the other hand, do not raise cholesterol or promote atherosclerosis. Mono- Concepts of Fitness and Wellness / Concepts of Physical Fitness Web Review - Chapter 16 – pg. 5 unsaturated fats (which have only 1 double bond) such as olive oil, canola oil have been found to lower cholesterol and have beneficial effects on lipid profiles. The same beneficial effect is found for the omega-3 fatty acids in seafood. There has been considerable interest in recent years in a type of fat known as a “trans-fatty acid” which have been found to be highly atherogenic. This type of fatty acid is created when an unsaturated fat (e.g. an oil) is converted into a saturated one in the process of hydrogenation. The hydrogenation process extends the shelf life of products and makes the fat more solid at room temperature. For example, this is how vegetable oils are converted into margarine that can be more conveniently spread onto foods. To complete the hydrogenation process, hydrogen is bubbled into the oil until the hydrogen molecules bond to the “free” carbon molecules. The resulting compound becomes a saturated fat known as a “trans” fatty acid because the chemical bond is different than in other fats. From a dietary standpoint, foods that are hydrogenated may be as harmful as saturated fats. Web Review - Chapter 16 – pg. 6 Concepts of Fitness and Wellness / Concepts of Physical Fitness Web16-4: Composition of Oils (p. 313) Because oils are liquids at room temperature many people assume that they are completely unsaturated. A closer look reveals that not all oils are created equal. Oils vary considerably in the percentage of saturated, poly-unsaturated and mono-unsaturated fats that they contain. Type Saturated Polyunsaturated. Monounsaturated Safflower 9 75 16 Sunflower 10 66 24 Corn 13 59 28 Soybean 14 58 28 Sesame 14 42 44 Peanut 17 32 51 Palm 49 9 42 Olive 14 8 78 7 35 58 Canola Note: values reflect percentages of each type of fat. In selecting oils, it is best to choose oils that are high in mono-unsaturated fats and low in saturated fats. Good choices for the kitchen are olive oil and canola oil since they have the larger percentage of mono-unsaturated fats. This type of fat has actually been shown to be good for health since it can actually lower blood levels of LDL cholesterol. Concepts of Fitness and Wellness / Concepts of Physical Fitness Web Review - Chapter 16 – pg. 7 Web16-5: Comparing Simple and Complex Carbohydrates (p. 314) Carbohydrates are the body’s primary source of energy. There are two types of carbohydrates (simple and complex). They each are composed of the same three elements (carbon, hydrogen, and oxygen) - these are also the same components that also make up dietary fat – but they have different functions and properties in the body. Simple Carbohydrates: Simple carbohydrates are made up of individual sugar molecules (shown as a G for glucose). They are found in candy, soda, fruit and other sweet food. The molecules can be made up of either one (monosaccharide) or two (disaccharide) sugar units. Three types of monosaccharides are: fructose, glucose, and galactose. Complex Carbohydrates: Complex carbohydrate molecules are made up of longer chains of sugar units or simple sugars. They are often called polysaccharides, which simply means many saccharides. Complex carbohydrates are found in starchy foods such as potatoes, rice, pasta and bread as well as vegetables. Complex carbohydrates also contain dietary fiber. Puzzling Questions about Carbohydrates: 1. If starches are sugars then why don’t they taste sweet? The difference in taste is due to the length or size of the molecule. Complex carbohydrates are large molecules and they simply do not fit on the receptors of the taste buds on the tongue. As a polysacchride dissolves and is broken down by digestive enzymes in the mouth the molecules become smaller and start to taste sweeter. 2. Why are complex carbohydrates considered as “good foods” while simple sugars are considered “bad foods”? Complex carbohydrates and simple carbohydrates are basically made up of the same chemical components (sugar units or sacharide molecules). Despite these similarities, they are processed and used very differently within the body. Because simple sugars are made up of individual units they cause large increases in blood sugar which causes the body to release the hormone insulin. Insulin causes the sugars to be taken up and tends to promote the deposition of fat. Because complex carbohydrates have to be broken down one at a time, they do not cause a large increase in insulin. They therefore do not get stored as readily as simple sugars do. The excessive fluctuations in blood glucose levels caused by consumption of simple sugars can also lead to Concepts of Fitness and Wellness / Concepts of Physical Fitness Web Review - Chapter 16 – pg. 8 decreases in insulin sensitivity and an increased risk for Type 2 diabetes. In addition to these differences, complex carbohydrates tend to contain other nutrients such as vitamins and minerals as well as dietary fiber while simple carbohydrates tend to have little nutritional value. Thus, while the two compounds look alike they have very different effects on the body. 3. If fruit is considered a simple carbohydrate why is fruit considered to be healthy but other simple sugars are not? The sugars in fruit are composed of fructose molecules instead of glucose. Fructose does not cause increases in blood sugar and therefore doesn’t lead to any of the metabolic imbalances that are associated with simple sugars (see question 2). Fruit also is packed with vitamins, minerals and fiber while most simple sugar foods are just “empty calories”. Concepts of Fitness and Wellness / Concepts of Physical Fitness Web Review - Chapter 16 – pg. 9 Web16-6: Carbohydrate Loading (p. 321) Carbohydrates are the bodies preferred source of energy during exercise. The body has only a limited supply of glucose available in the bloodstream. During exercise, the surge of adrenaline causes the hormone glucagons to be released. This hormone allows the body to break down some of its stored sugar (stored as a compound called glycogen) and release it into the blood so it can be used by the exercising muscles. The body has a limited supply of glycogen (about 2000 kcal). If exercise is performed for long periods of time such as marathon running the supply of glycogen gets pretty low. When the supply gets to a critically low level, the body begins to restrict the release of glycogen in order to save glucose for the brain. This forces the body to begin having to use other energy sources (primarily fat) to contribute to the production of energy. While fat provides a good source of energy during aerobic exercise, it is harder for the body to produce the energy as quickly as it is needed and the person must usually slow down. This metabolic state is typically called “hitting the wall” because you feel quite sluggish and tired without the same supply of available glucose. Once the fat metabolism catches up the body can continue exercising more vigorously. To avoid hitting the wall, many endurance athletes try to maximize their level of stored fuel (glycogen) prior to racing or competing in a major endurance activity. An early study by Bergstrom in 1967 demonstrated that the formation of glycogen is enhanced following a diet high in carbohydrate. He also observed that endurance time is greater among the athletes consuming a higher carbohydrate diet. The practice of consuming a higher percentage of carbohydrates in the diet became known as “carbohydrate loading”. It is important to point out that the key to carbohydrate loading is not necessarily to eat more food but to eat a good sized meal that is comprised mainly of carbohydrates. Individuals interested in further information on carbohydrate loading are advised to consult a registered dietician (RD). Concepts of Fitness and Wellness / Concepts of Physical Fitness Web Review - Chapter 16 – pg. 10 Web16-7: Supplemental Readings (p. 325) Alaimo, K. et al. “Dietary Intake of Vitamins, Minerals, and Fiber of Persons Ages 2 Months and Over in the United States.” Vital and Health Statistics: Advance Data 258(1994):1. Albert, C. M. et al. 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