While fats previously had a bad reputation, it’s now more commonly understood that we need fats for a variety of reasons that include energy production, storage for later use, and assistance with essential functions such as transporting fat-soluble vitamins, maintaining cell membranes and insulating/protecting us.

Traditional Indigenous cultures often included fat-rich foods. Indigenous knowledge recognizes the significance of these foods in providing essential energy and nutrients for various life stages and activities. For example, Indigenous communities have traditionally relied on sources of healthy fats like wild game, fish, and nuts, which are not only calorically dense but also offer important nutrients needed for optimal growth, development, and physical performance.

Providing Energy

Lipids provide 9 kcal per gram and are a major source of energy, particularly during rest and low-intensity exercise. During exercise, stored lipids can be mobilized from the muscle, adipose tissue and blood lipoproteins. The degree to which lipids are used will depend on the exercise intensity and duration, training status, time of last meal, as well as the dietary intake of lipids. The lower the intensity of exercise, the greater the proportion of lipids used to produce energy. However, as exercise intensity increases, this proportion shifts towards carbohydrates being the major energy source. As the body has limited glycogen stores, the longer the exercise duration, the greater the proportion of energy coming from fats. Endurance training causes a metabolism shift towards more lipid use and sparing of glycogen. After a fast (e.g., overnight), lipids dominate one’s energy supply. Those who consume a high-carbohydrate, low-fat diet experience reductions in the oxidation of fats, whereas those on a low-carbohydrate high-fat diet, experience increases in the oxidation of fats.

Hormones such as epinephrine increase lipolysis, and hormones such as insulin decrease lipolysis. Once fatty acids have been liberated from their storage site, they are transported in the blood attached to albumin, and delivered to the muscle. When in the muscle, fatty acids undergo beta-oxidation to produce ATP, which provides the energy necessary for muscle contraction and bodily functions.

Storing Energy

The excess energy from the food we eat is digested and incorporated into adipose tissue, or fatty tissue. Most of the energy required by the human body is provided by carbohydrates and lipids. As discussed in the Carbohydrates chapter, glucose is stored in the body as glycogen. While glycogen is a readily accessible source of energy, lipids primarily function as an energy reserve. As you may recall, glycogen is quite bulky with heavy water content, thus the body cannot store too much for long. Alternatively, fats are packed together tightly without water and store far greater amounts of energy in a reduced space. A single gram of fat is densely concentrated with energy—it contains more than twice the amount of energy than a single gram of carbohydrate. Energy is needed to power the muscles for all the physical work and play an average person or child engages in. For instance, the stored energy in muscles propels an athlete down the track, spurs a dancer’s legs to showcase the latest fancy steps, and keeps all the moving parts of the body functioning smoothly.

Unlike other body cells that can store fat in limited supplies, fat cells are specialized for fat storage and can expand almost indefinitely in size. An overabundance of adipose tissue can result in undue stress on the body and can be detrimental to your health. A serious impact of excess fat is the accumulation of too much cholesterol in the arterial wall, which can thicken the walls of arteries and lead to cardiovascular disease. Thus, while some body fat is critical to our survival and good health, large quantities can be a deterrent to maintaining good health.

Regulating and Signaling

Triglycerides control the body’s internal climate, maintaining a constant temperature. Those who don’t have enough fat in their bodies tend to feel cold sooner, are often fatigued, and have pressure sores on their skin from fatty acid deficiency. Triglycerides also help the body produce and regulate hormones. For example, adipose tissue secretes the hormone leptin, which regulates appetite. In the reproductive system, fatty acids are required for proper reproductive health. Women who lack proper amounts may stop menstruating and become infertile. Omega-3 and omega-6 essential fatty acids help regulate cholesterol and blood clotting and control inflammation in the joints, tissues, and bloodstream. Essential fatty acids also play a role in cell membrane structure, preventing DNA damage, fighting infection, and promoting fetal growth and development. Fats also play important functional roles in sustaining nerve impulse transmission, memory storage, and tissue structure. More specifically, lipids are focal to brain activity in structure and function. They help form nerve cell membranes, insulate neurons, and facilitate the signalling of electrical impulses throughout the brain. Lipids, specifically polyunsaturated fatty acids and phospholipids, are critical to cell membranes and determine what enters and exits the cell.

Insulating and Protecting

Did you know that up to 30 percent of our body weight is comprised of fat tissue? Some of this is made up of visceral fat or adipose tissue surrounding delicate organs. Vital organs such as the heart, kidneys, and liver are protected by visceral fat. The composition of the brain is outstandingly 60 percent fat, demonstrating the major structural role that fat serves within the body. You may be most familiar with subcutaneous fat, or fat underneath the skin. This blanket layer of tissue insulates the body from extreme temperatures and helps keep the internal climate under control. It pads our hands and buttocks and prevents friction, as these areas frequently come in contact with hard surfaces. It also gives the body the extra padding required when engaging in physically demanding activities such as ice- or roller skating, horseback riding, or snowboarding.

Aiding Digestion and Increasing Bioavailability

The dietary fats in the foods we eat break down in our digestive systems and begin the transport of precious micronutrients. By carrying fat-soluble nutrients through the digestive process, intestinal absorption is improved. This improved absorption is also known as increased bioavailability. Fat-soluble nutrients are especially important for good health and exhibit a variety of functions. Vitamins A, D, E, and K—the fat-soluble vitamins—are mainly found in foods containing fat. Some fat-soluble vitamins (such as vitamin A) are also found in naturally fat-free foods such as green leafy vegetables, carrots, and broccoli. These vitamins are best absorbed when combined with foods containing fat. Fats also increase the bioavailability of compounds known as phytochemicals, which are plant constituents such as lycopene (found in tomatoes) and beta-carotene (found in carrots). Phytochemicals are believed to promote our health and well-being. As a result, eating tomatoes with olive oil or salad dressing will facilitate lycopene absorption. Other essential nutrients, such as essential fatty acids, are constituents of fats themselves and serve as building blocks of a cell.

Note that removing the lipid elements from food also takes away the food’s fat-soluble vitamin content. When products such as grain and dairy are processed, these essential nutrients are lost. Manufacturers replace these nutrients through a process called enrichment.