"Many of the health issues associated with poor eating habits are a result of an energy imbalance. Most Americans are obtaining more energy from food than they actually need to function in their daily lives. With a large percentage of Americans engaging in no physical activity, this excess of energy is stored as fat in the body. This food energy is measured in calories, also known as kilocalories (kcals). A kilocalorie is the amount of energy needed to raise 1 kilogram of water 1 degree Celsius, but food labels use the term calorie to describe the amount of energy in the individual foods described. The term calorie is used in this textbook to describe food energy.\n\nIdeally, when we consume and obtain energy from our food, we will primarily eat nutrient-dense foods. A nutrient is a compound that provides a needed function in the body. Nutrients can be further classified based on the amount needed in the body. The six essential nutrients are the nutrients that our bodies need in order to survive. They can be broken into two categories: macronutrients and micronutrients.\n\nMacronutrients are nutrients needed in larger amounts. There are four macronutrients: carbohydrates, which provide 4 calories per gram; fats, or lipids, which provide 9 calories per gram; protein, which provides 4 calories per gram; and water, which contains 0 calories. Carbohydrates, protein, and fats provide energy. However, alcohol is another energy source in the diet that is not a nutrient. Alcohol is not a nutrient, but it does provide energy and has 7 calories per gram.\n\nMicronutrients are nutrients needed in smaller amounts, but they are still considered essential. There are two groups of micronutrients: vitamins and minerals."