Calories are units of energy that can be found in the foods that we eat and the liquids we drink; they are either used up/burned to produce energy, or stored as excess fat if unused. The recommended amount of calories to eat per day varies from person to person, and has a lot to do with age, weight, height, activity level, sex, and overall physical health (Nordqvist, 2012). http://www.medicalnewstoday.com/articles/245588.php
To maintain a healthy weight, people need to burn as many calories as they eat. Losing weight requires burning off more calories than you eat, and people gain weight when they consume more calories than they burn over a period of time. There is a tool called a BMR calculator, which uses your height, weight, age, and other factors to calculate the number of calories your body will use if you were to engage in no kind of physical activity all day. This amount can then be adjusted based on a person’s activity level (Weight Loss Resources, n.d.). https://www.weightlossresources.co.uk/calories.htm
Health Canada has an equation that can be used to calculate one’s daily caloric need; realistically, however, it is not very user-friendly and can confuse people (Health Canada, 2010). http://www.hc-sc.gc.ca/fn-an/nutrition/reference/table/index-eng.php#eeer
The website for the Canada Food Guide also has a page for estimated energy requirements, in which they put the average caloric needs of all age groups, into two tables, split into male and female categories. This table, however, does not accurately display the amount of calories a person should be eating, and this will be discussed further in Chapter 2 (Health Canada, 2014). http://www.hc-sc.gc.ca/fn-an/food-guide-aliment/basics-base/1_1_1-eng.php
Macronutrients are the nutrients that provide a person with calories, the unit of energy mentioned previously. They are referred to as “macro” nutrients because a person requires a large amount of them in comparison to “micro” nutrients. Nutrients are what the body requires for growth, metabolism, and other bodily functions. There are three types of macronutrients which all serve different yet essential purposes in the body (Saleem, 2013). http://dietdatabase.com/macronutrients-and-micronutrients/
Carbohydrates are the nutrients that the body uses to create glucose, the body’s main energy source, which is why they are typically needed in the largest amounts (aside from water) (Saleem, 2013). http://dietdatabase.com/macronutrients-and-micronutrients/ There are 4 calories of energy per gram in carbs.
There are several other reasons why carbs are important to have in one’s diet. They are easily used by the body for energy; all of the tissues and cells in our body can use glucose for energy; and they’re needed for the central nervous system, the kidneys, the brain, the muscles (including the heart) to function properly. The can be stored in muscles and the liver and can later be used for energy, are important in intestinal health and waste elimination, and can also help the body utilize its fat stores (McKinley Health Centre, 2014). http://www.mckinley.illinois.edu/handouts/macronutrients.htm
Complex vs Simple Carbs
There are two kinds of carbohydrates, which can be categorized into good carbs and bad carbs - or, more technically, complex carbs and simple carbs.
Simple Carbs are considered to be the “bad” carbs. They are simple sugars, with a simple chemical structure, that can be found naturally in foods - such as fruits, milk, and milk products - and artificially when added to foods that are processed and refined. These sugars have a high glycemic index (GI) which means, when consumed, they are converted into glucose and enter your bloodstream fairly quickly. This results in a sudden burst of energy but because they are consumed so quickly, the feeling is followed by a plateau or crash which leads to hunger and cravings (Saleem, 2013). http://dietdatabase.com/macronutrients-and-micronutrients/
Simple carbohydrates can be further divided into two types: monosaccharides and disaccharides. Monosaccharides consist of a single sugar molecule, and include sugars such as fructose and glucose. Disaccharides consist of two monosaccharides that have bonded together, and include compounds such as lactose and sucrose (FitDay, 2012). http://www.fitday.com/fitness-articles/nutrition/carbs/simple-vs-complex-carbohydrates.html#b
Complex Carbs are considered the “good” carbs. They are also referred to as polysaccharides - 3 or more monosaccharides bonded together - and can be categorized into starches and dietary fibres. Starches take a lot longer to break down than simple sugars, and have a lower glycemic index than their simple carb counterparts. This means that they will be digested slowly and will enter the bloodstream as glucose more gradually, providing the body with energy and creating a feeling of fullness over a longer period of time. Some foods that contain complex carbs include grains such as pasta, bread, and oatmeal, as well as many nuts, seeds, and legumes (Saleem, 2013). http://dietdatabase.com/macronutrients-and-micronutrients/
The other type of complex carb, dietary fibre, is essential for your health and can help you maintain a healthy weight while also lowering your risk for heart disease and diabetes. It is found mainly in fruits, vegetables, and some whole grains and legumes, and it includes all parts of plant food that can’t be digested and absorbed by the body (this is also why it is best known for its ability to keep bowel movements regular). It can be further categorized into soluble and insoluble fibre. Soluble fibre can dissolve in water and help lower blood cholesterol as well as glucose levels in your blood. This kind of fibre can be found in oats, peas, beans, barley, and some citrus fruits. Insoluble fibre, on the other hand, can’t dissolve in water and instead promotes the movement of substances through the digestive system, which is what helps those who struggle with constipation. Good sources of insoluble fibre include whole wheat foods, legumes, nuts, and some vegetables like green beans and potatoes. The institute of medicine recommends that men under 50 eat around 38 grams of fibre a day, and that women under 50 eat around 25 grams. These values decrease slightly for adults over age 50 (Mayo Clinic, 2012). http://www.mayoclinic.org/healthy-living/nutrition-and-healthy-eating/in-depth/fiber/art-20043983
It is typically recommended that 55-65% of one’s daily caloric intake come from carbohydrates, and that at least 80% of that comes from complex carb (Rosenbloom, 2013). http://www.canadianliving.com/health/nutrition/calories_protein_carbohydrates_and_fat_how_much_do_i_need_2.php
Fats are organic molecules, and are made up of hydrogens and oxygens joined together to create long chains called hydrocarbons. Because these molecules can be constructed in several different ways, there are many different kinds of fats, and they can have either healthy or unhealthy qualities. In our bodies, fats are responsible for normal growth and development, providing a source of energy, absorbing certain vitamins (like vitamins A, D, E, K, and carotenoids), providing cushioning for the organs, maintaining cell membranes, and providing taste, consistency, and stability to foods (Andrews, n.d.). http://www.precisionnutrition.com/all-about-healthy-fats
In dietary terms, there are three main types of fats: saturated, monounsaturated, and polyunsaturated. They are split into these categories based on their chemical properties. Saturated fats have no double bonds and are therefore “saturated” with hydrogen atoms, causing them to be solid at room temperature; these fats include any animal fats or tropical oils (e.g. coconut, palm). Unsaturated fats, on the other hand, have one or more double bonds between carbons; monounsaturated have one double bond, while polyunsaturated have at least two. Some foods containing monounsaturated fats include olive oil, avocados, and nuts, while foods containing polyunsaturated fats include flax, fish oil, and most seed oils (Andrews, n.d.). http://www.precisionnutrition.com/all-about-healthy-fats
Furthermore, there are other fats that have been introduced into the human diet more recently and tend to appear in processed foods; these are the trans fats, which contain hydrogenated fats and oils. Trans fats do not occur naturally, but are produced when a liquid vegetable oil is chemically altered by having hydrogens added to it, turning it into a solid fat. This process is called hydrogenation. Trans fats are often added to processed foods because of their ability to “improve taste and texture and help the food stay fresh longer” (EatRight Ontario, n.d.). http://www.eatrightontario.ca/en/Articles/Fat/Tackling-Trans-Fat.aspx#.U5OOafmwJBc
Fat is probably the most misunderstood macronutrient of the three. More often than not, people tend to believe that eating fat will make you fat. This is a common misconception; eating fat, period, will not cause you to gain weight. Eating excessive quantities of the wrong kind might, however, since eating more calories than you burn is the easiest way to gain weight (Saleem, 2013). http://dietdatabase.com/macronutrients-and-micronutrients/ There is a place for “healthy fats” in our diet, as they are an important source of energy (1 gram has 9 calories) and also act as insulators and protectors of vital parts of our body. There is strong evidence to suggest that fats can aid in cardiovascular protection, improve body composition, and ease depression (Andrews, n.d.). http://www.precisionnutrition.com/all-about-healthy-fats There has also been some average evidence to suggest that consuming fats can reduce your risk for cancer, preserve your memory and eye health, reduce symptoms of ADD and ADHD, and reduce the potential for aggressive behaviour (LiveScience, 2012). http://www.livescience.com/20429-good-fats-good-brain.html
Different diets will recommend different amounts of fats that should be consumed per day, but the general consensus is that 20-35% of your daily caloric intake should come from fats, and that these should be “healthy fats” (Rosenbloom, 2013). http://www.canadianliving.com/health/nutrition/calories_protein_carbohydrates_and_fat_how_much_do_i_need_2.php
Unlike with carbohydrates and fats, people generally understand that protein is necessary in their diet, and they typically meet their daily protein needs. Proteins are considered to be the building blocks of life; they are made up of a chain of amino acids and used by the body in structure, maintenance, and repair. Proteins are found in every cell of your body and are needed for growth, tissue repair, immune function, making essential hormones and enzymes, providing energy when carbohydrates are not available, and preserving lean muscle mass (McKinley Health Centre, 2014). http://www.mckinley.illinois.edu/handouts/macronutrients.htm
When proteins are digested, the amino acids are left behind and used to further break down food. Amino acids can be found in foods such as meats, fish, milk, and eggs, as well as in legumes, nuts, beans, and some grains; contrary to a decreasingly popular misconception, you don’t need to eat animal products in order to get the proper amount of protein/amino acids in your diet. Proteins, when broken down into amino acids, can be further classified into two different types of amino acids: essential and nonessential. Essential amino acids are ones that cannot be synthesized by the body, and must therefore come from our diet (A.D.A.M., 2011). http://www.nlm.nih.gov/medlineplus/ency/article/002467.htm The nine essential amino acids are listed below:
They do not all need to be eaten at one meal, but it is important to balance them over the course of a day. Some foods that are high in these essential amino acids are eggs, animal meats (beef, pork, chicken, turkey), soybeans, and quinoa. These foods are all considered complete proteins, meaning that a serving will contain all nine of the essential amino acids (Diggs, 2013). http://www.livestrong.com/article/249606-foods-high-in-essential-amino-acids/
Nonessential amino acids can be synthesized by the body, and come from either the essential amino acids or the regular breakdown of proteins. The term “nonessential” does not imply that these amino acids are any less important; it is simply that the body is able to create them on its own, and it is therefore not essential or necessary for a person to get these amino acids from an outside source (FitDay, 2012). http://www.fitday.com/fitness-articles/nutrition/vitamins-minerals/understanding-non-essential-amino-acid-function.html#b The nonessential amino acids are listed below:
Based on the recommendations of the other macronutrients, the most widely accepted amount of protein to eat (for Canadians) is 10-35% of the daily caloric intake (Rosenbloom, 2013). http://www.canadianliving.com/health/nutrition/calories_protein_carbohydrates_and_fat_how_much_do_i_need_2.php
Micronutrients differ from macronutrients in the sense that we need much smaller amounts of these nutrients. Nonetheless, micronutrients are essential for maintaining proper health, and deficiencies in micronutrients can lead to serious health problems. These nutrients are the ones responsible for the healthy functioning of all of your body’s systems, from the growth of your bones to the functional state of your brain (FitDay, 2012). http://www.fitday.com/fitness-articles/nutrition/vitamins-minerals/micronutrients-what-they-are-and-why-theyre-essential.html#b
Micronutrients are more commonly known as vitamins and minerals. They include vitamins such as vitamin A, B-complex, C, D, E, and K, and minerals such as calcium, magnesium, iron, zinc, sodium, and potassium. Listed below are some of the common vitamins and minerals, and what their functions are in the body:
normal bone and tooth development, development and maintenance of night vision, and maintaining health of skin and membranes
aids in normal growth and development; factor in energy metabolism and tissue formation, aids in red blood cell formation, may play a role in the prevention of neural tube disorders
development and maintenance of bones, cartilage, teeth and gums
formation and maintenance of bones and teeth
enhances calcium and phosphorus absorption and utilization
protects the fat in body tissues from oxidation
formation and maintenance of bones and teeth
energy metabolism, tissue formation and bone development
red blood cell formation
energy metabolism and tissue formation
normal cell function and regulation of blood volume
normal cell function and proper nerve, muscle and blood cell function
(Heart & Stroke Foundation, 2006) http://www.healthcheck.org/page/function-nutrients
Having enough micronutrients every day is not very difficult. The key is to eat a a balanced diet that incorporates a rainbow of fruits and vegetables - things like cherries, grapes, bananas, and carrots - and pays particular attention to leafy green vegetables. Eating nuts and whole grains on top of this will almost guarantee a full serving of all the major micronutrients (FitDay, 2012). http://www.fitday.com/fitness-articles/nutrition/vitamins-minerals/micronutrients-what-they-are-and-why-theyre-essential.html#b
The Body’s Energy Pathways
(Many of the concepts in this section can be found in more detail in the Exercise Science: An Introduction to Health and Physical Education textbook.)
Now that you know about the different kinds of nutrients your body needs, you can apply this knowledge to the body’s energy systems and metabolic pathways. The body’s main form of “currency” is called adenosine triphosphate, or ATP. It is a high energy molecule that consists of three phosphates, one of which can be cleaved from the molecule to produce energy and an ADP molecule (adenosine diphosphate). Your body has two energy systems; one can proceed without oxygen and is called the anaerobic system, while the other requires oxygen and is called the aerobic system. The anaerobic system is the first to act in exercise and occurs fairly quickly for powerful but short-lived physical exertions. It is divided into two metabolic pathways; the anaerobic alactic system, and the anaerobic lactic system (Temertzoglou, 2003).
The anaerobic alactic system, also known as the ATP-PC system, is powered by phosphocreatine (PC), a readily accessible compound stored in the muscle. PC is a high energy molecule that can have a phosphate broken off from it in order to convert ADP back into ATP, meaning that it can help the body sustain ATP levels during this short period of intense activity. This system would be most useful in an activities such as weightlifting, ski jumping, throwing, or sprinting 100m, activities that require a lot of power for a short period of time, about 10-15 seconds maximum (Temertzoglou, 2003).
Because muscles do not hold a lot of phosphocreatine, this pathway stops being effective quite quickly and another metabolic pathway must come into play. The anaerobic lactic system, also known as glycolysis, is the second energy pathway that your body uses during physical activity; the ATP produced by this pathway will give the athlete an extra 1-3 minutes of peak performance. Glycolysis, while a pathway on its own, is also the first step into the aerobic system pathway. In this stage, glucose is partially broken down to provide the body with a few more ATP molecules relatively quickly, again without the need for oxygen. In glycolysis, the main goal is to produce pyruvate, which can further be used in the aerobic pathway. However, if the body is not receiving enough oxygen, the pyruvate will instead be converted into lactic acid, which hinders the breakdown of glucose and decreases the ability of muscles to contract. This would occur in power sports that take a bit more time, such as a 400m sprint, cycling and track events, and alpine skiing. After this point, the anaerobic systems cease to be useful, and a more effective pathway is used (Temertzoglou, 2003).
The Aerobic System
If an athlete wants to maintain an intense activity for over 90 seconds, the aerobic system must come into play. Also known as cellular respiration, this system is able to use fats and proteins as energy sources, in addition to glucose, a carbohydrate, and is active in the presence of oxygen. For exercise that lasts over 20 minutes, fats become the primary resource; proteins are not used until the situation becomes dangerous, such as if a person were starving (PSE4U notes, 2014). This energy system produces almost 20 times more ATP than the anaerobic system, and can sustain an athlete for quite some time, at least until other physiological limits are reached. Cellular respiration involves three sub-pathways, one of which is glycolysis. The other two - the Krebs Cycle and the electron transport chain - each produce 2 and about 32 ATP respectively. This system is useful for activities lasting longer than about 90 seconds, including anything from synchronized swimming and figure skating, to cross-country skiing and a triathlon (Temertzoglou, 2003).
Glucose, Fats, Proteins
15 sec - 3 min
120 sec and up
Types of activities
power and speed
Types of exercise
sprints, jumping, weightlifting
200-800m runs, hockey shifts
Surely all of this information means something, right? In the next few chapters, you will see that the role of the various macronutrients in a person's diet - whether they be an athlete or a regular person - is very important. A power athlete, for example, will not eat the same diet as an endurance athlete or a person who does minimal physical activity, because his/her energy requirements are different. Different macronutrients will have different effects on the anaerobic and aerobic energy systems, and your need for these macronutrients will vary based on which systems you're most likely to use in a typical day.
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