Fats are a group of substances found in food. They have one major property in common: They are not soluble in water. If you have ever tried to mix vinegar and oil when making salad dressing, you have observed the principle of water and fat solubility firsthand.
Fats are actually a subcategory of the fat-soluble substances known as lipids. Lipids include fats, oils, and cholesterol. Dietary fats such as butter, margarine, and shortening are often distinguished from oils by their property of being solid at room temperature. This physical difference between fats and oils is due to their chemical structures. Dietary fats have the following roles in our body:
Fats in Foods Supply Energy and Fat-Soluble Nutrients
Dietary fats are a concentrated source of energy. Each gram of fat consumed supplies the body with 9 calories worth of energy. That’s enough energy for a 160-pound person to walk casually for a little over two minutes or to jog at a slow pace for about a minute. Fats in food supply the essential fatty acids and provide the fat-soluble vitamins D, E, K, and A. So, part of the reason we need fats in our diet is to get a supply of the essential nutrients they contain. Diets containing little fat (less than 20% of total calories) often fall short on delivering adequate amounts of essential fatty acids and fat-soluble vitamins.
Fat Contributes to the Body’s Energy Stores
Fat consumed as part of a dietary intake that exceeds calorie need is converted to triglycerides and stored in fat cells. A pound of body fat can provide approximately 3,500 calories of energy to the body when needed. Body fat is not just skin deep. Fat is also located around organs such as the kidneys and heart. It’s there to cushion and protect the organs and keep them insulated. Cold-water swimmers can attest to the effectiveness of fat as an insulation material. They purposefully build up body fat stores because they need the extra layer of insulation.
Fats Increase the Flavor and Palatability of Foods
Although pure fats by themselves tend to be tasteless, they absorb and retain the flavor of substances that surround them. Thus, fats in meats and other foods pick up flavors from their environment and give those flavors to the food. This characteristic of fat is why butter, if placed next to the garlic in the refrigerator, tastes like garlic.
Fats Contribute to the Sensation of Feeling Full
As they should, at 9 calories per gram, Fats tend to stay in the stomach longer than carbohydrates or proteins and are absorbed over a longer period of time. Their presence in the stomach and small intestine triggers a feeling of fullness. That’s why foods with fat stick to your ribs.
Fats are a Component of Cell Membranes, Vitamin D, and Sex Hormones
Some types of fats give cell membranes flexibility and help regulate the transfer of nutrients into and out of cells. Others serve as precursors to vitamin D and sex hormones, such as estrogen and testosterone.