Fats provide the body with a key source of energy. Although glucose is the main source of energy for the brain and nervous system, muscle tissues prefer fats for energy. During exercise, muscles rely on fats for energy after glucose and glycogen (stored glucose) have been depleted.
Fats also insulate and protect our bodies and vital organs, including the brain. About 15-30 percent of our total body weight comes from stored fat. The two main types of fat in our bodies are visceral fat and subcutaneous fat.
Visceral fat is buried below the body’s muscle tissue. It surrounds vital organs to cushion and protect them. Women usually have more body visceral fat than men and tend to store more in their breasts, hips, and thighs as a way of protecting organs involved in reproduction. Having excess visceral fat in the lower part of the body appears to be less harmful than having it in the abdominal area, where men tend to accumulate it. Visceral fat in the abdominal area is believed to secrete powerful chemicals that can increase the risk for diseases such as heart disease, diabetes, hypertension, metabolic syndrome, and breathing problems.
Subcutaneous fat is the fat you can see; it lies just beneath the skin. This fat also protects and insulates the body.
Fats also carry some important vitamins (including vitamins A, D, E, and K), carotenoids, and other substances that dissolve in fat to help them be better absorbed and used by the body. Fats are also used to create and maintain cell membranes (the outer layer or cells that protect them) and help maintain healthy skin and nails.
Dietary fats, also known as dietary triglycerides, are found in a variety of foods from both animal and plant sources. They are more than twice as energy-dense as the other macronutrients: carbohydrate and protein. Fat provides 9 calories per gram, although carbohydrate and protein each contain only 4 calories per gram. (Incidentally, alcohol, not a nutrient but still a source of calories, falls somewhere in between and provides 7 calories per gram).
Fats also promote satiety, or the feeling of fullness. Fats in foods add a lot to their taste, texture, smell, and mouth feel. Fats in foods are versatile, can be heated to high temperatures without degrading, and can be used in countless cooking methods to create highly palatable foods.
If you consume too much dietary fat, your body can efficiently store it as body fat. This stored fat can be easily accessed when your calorie needs increase – for example, during periods of growth (such as in pregnancy or childhood), during illness or after an injury, or during a natural disaster or at times when food is scarce. In normal circumstances, too much dietary fat can put you at risk for being overweight or for obesity, and too much of certain types of fats (including saturated and trans fats) can contribute to the development of heart disease and other diet-related diseases and conditions.
If you consume too little dietary fat, your body fat stores can become depleted. If you’re a woman, you might stop menstruating and have reproductive problems. Your skin might deteriorate, you might fell cold (because you have less body fat to warm you), and your organs and tissues might be at more risk for injury. This can be a problem, especially for older people who might have a chronic disease. Children who don’t consume enough fat (it’s rare, but can happen) won’t get enough essential fats that they need to get from the diet. If they don’t consume enough calories, they don’t’ accumulate / have enough body fat (everybody needs some body fat), and they can literally stop growing. A deficiency is rare especially in the United States, but still kids need enough fat to grow optimally.
Carotenoids are a group of yellow, oranges and red pigments found in plant foods (most often in fruits and vegetables). They act as antioxidants to protect body cells against damage caused by free radicals (harmful substances found in the body and environment).
Triglycerides are made of three fatty acids jointed to a glycerol unit (an alcohol that forms the backbone of triglycerides). Triglycerides are found in fats and oils and foods made with tem as well s in meats, dairy products, nuts, and seeds.