This unit, we focused on health. But what exactly is health? In the beginning of the unit, our group-made definitions included keywords like "exercise" and "mental and physical health." As we learned in class, health is the measure of our body's efficiency and overall well being. Health can be thought of as a triangle, with the three sides of mental health, physical health, and social health. Mental health is how we think and cope with situations, and whether we suffer from mental illnesses or disorders. Physical health is our body's ability to function. Social health is how we react to others in our environment. Health can also be thought of as a columned building with 5 pillars: nutrition, exercise, sleep, stress, and social life. Each of these pillars is essential to the building's foundation, and if one pillar is skewed, the building is structurally weak and may collapse.
When our bodies are physically healthy, certain hormones known as the Big Four are doing their jobs correctly. The first of these hormones is insulin, the hormone that facilitates the movement of macro-nutrients into the cells and regulates the blood glucose levels. In western society, we tend to "overcarbsume," which can lead to insulin resistance, a dangerous condition that affects the body's ability to detect insulin's presence. The second hormone is leptin, which tells the brain how much fat there is on the body. It also regulates the energy intake and expenditure, controlling how much we eat and feel the need to get moving. When we have a lack of fat, no leptin is released, which tells the brain to eat and retain fat. When we have an excess of fat, leptin is released, which tells the brain to stop eating and increase activity. The third hormone is glucagon, which allows access to the body's glycogen storage for energy. This can be stimulated by low blood sugar, stress, or an intake of protein. The last hormone is cortisol, not so affectionately known as the "stress hormone" because it is prevalent in response to stress. It raises blood pressure by stimulating glycogen breakdown, and can be dangerous if elevated for long periods of time.
Now, to focus back on the pillars of health, let's look at nutrition. A nutrient is a substance in food that exerts a biological function and is necessary to live. The classes of different nutrients are carbohydrates, lipids, proteins, minerals, vitamins, fiber, water, and phytochemicals. The amount of each nutrient needed varies. In order to maintain a healthy diet, follow these four rules: Adequacy, Moderate, Variety, and Balance. Always look for nutrient dense foods, which have lots of nutrients for relatively low calories. Carbohydrates in food can be simple (mono/disaccharides) like fruits, dairy, honey, sugar, syrup, and agave; complex (polysaccharides) like grains, legumes, and tubers; or fiber (soluble or insoluble) like whole grains, which is resistant to digestion and prevents constipation. For carbohydrates, choose fiber rich foods, limit foods with added sugar, choose a variety of fruits and vegetables, and half of your grains should be whole grains. Lipids in food can be saturated like coconut oil, butter, cheese, or lard; unsaturated like olive oil, avocado, nuts,or canola oil; or trans-fat like hydrogenated oils in processed/fried foods. There are 4 main types of fat in food, polyunsaturated fats (PUFAs), monounsaturated fats (MUFAs), saturated fats (SFAs), and trans-fats (TFAs). PUFAs like omega 3 help with brain and heart health, but too much omega 3 can lead to inflammation. MUFAs increase HDL, the good cholesterol. SFAs increase LDL, the bad cholesterol. TFAs increase LDL and decrease HDL, hardening the arteries. Limit your fat intake to 25-30%, choose low fat or fat free dairy, avoid trans-fats, and increase your intake of omega 3. Proteins in food account for the 9 amino acids that our bodies can’t produce and must obtain from food. They provide energy, repair things, transport and store molecules, increase immunity, and more. Eat high protein foods with low fat. Vitamins maintain growth and normal metabolism, act as coenzymes, and can be antioxidants. Water accounts for ⅔ of the body’s overall weight. We are dependant on water to survive, and will die without it in a few days. It regulates our body temperatures, lubricates joints, makes up saliva, and more. In general, drink either 6-8 glasses a day or half your bodyweight in ounces.
Now, we look at exercise. There are four types of exercise: aerobic, muscle strengthening, bone strengthening, and flexibility. Aerobic, known as cardio or endurance, works muscles as groups and increases the heart rate. Muscle strengthening works muscles against a force or a weight, creating tiny tears in the muscle that heal to strengthen it. Bone strengthening pits force on bones that promotes bone strength. Flexibility increases the range of motion, but should not be counted toward overall minutes of exercise. When we exercise, we rely on different metabolic pathways for energy throughout our workouts. First we use the phosphagen pathway for high power, short exercises, relying on creatine phosphate. Then we use the glycolic pathway for lower power exercise up to 10 minutes, relying on glycolysis until the lactic acid concentration in the body is too high. Then we use the oxidative pathway for exercise upwards of 10 minutes, relying on cellular respiration for energy.
Next, let’s look at sleep. Sleep is a sensory shutdown where we are no longer aware of our environment, and is reversible. There are 2 types of sleep that we cycle through each night, REM and Non-REM sleep. During REM sleep, pronounced “rem” and named for the binocularly synchronous “rapid eye movement” that occurs, the brain is very active and most of the body is paralyzed as we experience vivid dreaming, indistinguishable from reality until we wake up. In Non-REM sleep, the eyes roll slowly and independently, and the body is not paralyzed. The body has an internal biological clock called the Circadian Rhythm, controlled by the hypothalamus which dictates when certain biological processes, such as sleep, take place each day. Melatonin, the hormone secreted by the pineal gland and known as the “Dracula hormone,” causes you to fall asleep, while cortisol, the “stress hormone,” causes you to wake up. If you do not sleep an adequate amount, you amass sleep debt, which can lead to sleep deprivation, impaired performance, mood swings, hunger, etc. All sleep debt must be paid at some point. 
Lastly, we shall look at the final pillar, stress. Stress is any event or demand that causes a predictable physiological response. Stress can be eustress, providing extra energy, momentum, and boosted productivity. But it can also be distress when it persists after the stressor is gone or persists daily. The first stage of stress is the alarm phase, or the “fight or flight” response. The body is ready for immediate physical activity. The second stage of stress is the resistance phase. Cortisol levels are high, and blood pressure and appetite are raised. The last stage of stress is exhaustion, where energy reserves deplete and feelings of lethargy raise. If this stage persists, death can occur. 
https://en.wikipedia.org/wiki/Food_pyramid_(nutrition)
https://commons.wikimedia.org/wiki/File:StressSymptoms.gif
https://en.wikipedia.org/wiki/Sleep_deprivation
https://en.wikipedia.org/wiki/Stress_(biology)
http://www.nhlbi.nih.gov/health/health-topics/topics/sleepapnea
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