• There are six classes of nutrients in the human diet. The macronutrients—nutrients that we need a lot of—include carbohydrates, protein, fats, and water. The micronutrients—nutrients we need a little of—include the vitamins and minerals. Of these, only carbohydrates, protein, and fats provide energy. That is, they provide calories that allow us to live, work, and function. The amount of energy you get from foods is measured in calories. Each of the energy-yielding nutrients provides different amounts of energy. For every gram of carbohydrate or protein you eat, you take in 4 calories. Fats are the most energy-rich nutrients, and they provide, gram for gram, more than twice the calories of the other nutrients at 9 calories per gram.
• One-pound equals 3,500 calories. Now that we know where our energy comes from—calories—let’s talk about energy balance. It’s a simple equation. When energy in—that’s calories—equals energy out—activity—your weight and energy stay the same. If you have more coming in than going out, you gain weight. If you have more going out than coming in, you lose weight. Most people are more concerned with weight loss than weight gain, so let’s figure out how to do this sensibly in a systematic and gradual way. In order to lose a healthy 1-2 pounds a week, you need to reduce your calories by 3500 to 7000 per week, or about 500 to 1000 calories per day. You can do this by eating less or exercising more or a combination of the two.

Hydration and Water

Although we typically think of nutrients as being foods, water is a nutrient, too. It is the most abundant component of the human body and about 50-70% of your body weight is water. You need it to carry the other nutrients in your body, to help your blood and other tissues get rid of wastes, to lubricate your joints, and maintain body temperature.  In less than a day, water deprivation can alter your body’s chemistry and metabolism, impair your judgment, and reduce your ability to carry out normal activities. Each day, water enters your body in liquids and foods, and your body produces some water as a byproduct of metabolism. Water leaves your body in the moisture of exhaled breath, in urine and feces, and through sweat evaporation. You can lose up to 2 quarts an hour in a hot environment or during intense activity. A 2.5% loss of all of your body’s water weight will result in a loss of performance. Water needs vary from person to person and from day to day, depending on a person’s activity level, environment (hot or cold, humid or dry), and food.

Vitamins and Minerals

Vitamins and minerals are vital to life. We get our vitamins and minerals from our diets. One exception to the rule is vitamin D, which our bodies produce following exposure to sunlight. There are two types of vitamins: fat soluble and water soluble. This just refers to how your body absorbs them and then carries them in the bloodstream. It also emphasizes how important fats and water are to our diets. Without them, we can’t absorb vitamins. Sometimes an individual’s needs can’t be met by the food supply because of a medical condition. Such individuals might require vitamin or mineral supplements. The fat-soluble vitamins can be stored in your body, primarily in your liver. For this reason, they can be toxic if you take too much. We typically only get concerned about taking in too much of these vitamins when people are taking them in supplement form. It’s hard (but not impossible) to get too much from the diet. There are 8 known B vitamins. They play many important roles from metabolism of fats, carbs, and protein to the production of red blood cells. They’re found in meats, fruits, vegetables, grains, and fortified foods such as breakfast cereals. The best source for B vitamins is a balanced diet. In spite of all they do for you, one thing B vitamins don’t do is give you energy. This is one of the most commonly heard nutrition myths. But they are involved in nearly every reaction in your body that processes and metabolizes the energy-yielding nutrients. They are necessary for the yield of energy but they don’t provide any directly. Minerals play many roles in metabolism, growth, and development. Key minerals include calcium, phosphorus, iron, magnesium, zinc, copper, sodium, chloride, and potassium. When minerals are dissolved in water, they all become electrolytes, but we usually refer only to sodium, chloride, and potassium as “electrolytes.”