What Role Does Fat Serve in Your Body?

The 1970s and 1980s diet lore demonized all dietary fat as increasing your risk for heart disease and weight gain. Moderate fat intake supports a healthy body and can help you feel more satiated so that you eat less overall and better manage your weight. Weight management doesn't mean you lose all body fat either -- you need some to support good health. Body fat consists of essential fat and storage fat.

Dietary Fat and Your Body

Dietary fat promotes a healthy, functioning body, and fat is an essential nutrient necessary for energy. When you exercise, for example, you use carbohydrates for the first 20 minutes. Exercise for longer than that, though, and fat fuels much of your effort.

Fat plays a role in the absorption of the fat-soluble vitamins: A, D, E and K. Fats also help you absorb certain antioxidants, known as carotenoids, such as lutein, lycopene, beta-carotene and zeaxanthin, which are found in yellow and orange vegetables. That's why eating a little fat with your veggies is a good idea, according to a Purdue University study published in 2012. Salad dressings containing monounsaturated fats, as opposed to fat-free dressings, helped study participants better absorb the carotenoids in the vegetables.

The fats you eat are incorporated in the membranes surrounding the cells in your body. These fats play a role in helping certain compounds -- such as proteins, ions, antioxidants and vitamins -- pass in and out of the cells through the membrane.

Essential fatty acids -- specifically linoleic and linolenic acid -- support eye and brain health, control inflammation and help with blood clotting. They're called "essential" because you need to get them from your diet and can't produce them on your own. Fatty fish, seeds and olive oil are quality sources.

Consuming fat also promotes healthy-looking skin and hair. The essential fatty acids known as omega 3s -- acquired from fatty fish and walnuts, for example -- help keep your scalp moist, so your hair grows lush. These fatty acids contribute to a moist, supple complexion, too, and fight premature aging.

Making Fat Part of Your Diet

Dietary fat has 9 calories per gram -- compared to the 4 calories per gram in protein and carbohydrates -- and ideally, fat should make up between 20 and 35 percent of your total calorie intake daily. For a person who eats 2,000 calories per day, that's between 44 and 78 grams daily. Include mostly healthy mono- or poly-unsaturated fats found in olive oil, avocados, nuts, fatty fish and seeds.

It's prudent to limit saturated fats, found in fatty cuts of meat and whole-milk dairy, to no more than 6 percent of your total daily calories. For a 2,000-calorie plan, that's about 13 grams maximum. Saturated fat may increase your levels of bad cholesterol, or low-density lipoprotein, and contribute to an increased risk of heart disease.

Avoiding trans fats may be one of the best things you can do for your health. They're oils that have been hydrogenated -- or chemically altered -- in order to have a longer shelf life. They cause the double whammy of raising the bad LDL cholesterol and lowering the good cholesterol, or high-density lipoprotein. Trans fats are in some restaurant foods and processed snacks, but the Food and Drug Administration is requiring manufacturers to phase them out by summer 2018.

The Role of Essential Body Fat

The fat that is part of your very body structure and function is known as essential fat. Women have more of it because hormones drive fat to be stored in the breasts, pelvis, hips and thighs to support pregnancy and breastfeeding. No matter how lean people appear, they all carry some body fat. Men have on average a minimum of 3 percent fat and women 13 percent to support life and reproductive functions.

Essential fat is found in the internal organs and the marrow of the bones. Fats make up some of the structure of the central nervous system as part of brain cell membranes. In addition, fat helps form special sheaths that surround nerves and enable them to transmit messages throughout the body.

Some fat also exists within your muscles. Your body mobilizes this intramuscular fat for energy, especially when you exercise at moderate intensity levels.

Storage Fat's Role in the Body

When you think of body fat, storage fat is likely what comes to mind. It makes your pants hard to zip and causes the jiggle at the back of your arms. Some storage fat is important to optimal body function, but too much body fat can be deleterious to your health. Your body mobilizes storage fat for energy when it doesn't have enough calories available to fuel your activity. The body houses two kinds of storage fat -- visceral and subcutaneous -- which serve different roles.

Visceral storage fat, often referred to as deep belly fat, weaves around your organs and provides some cushioning, but too much of it can release compounds into the bloodstream that raise your risk of chronic disease, such as type-2 diabetes and cardiovascular disease.

Subcutaneous fat sits just under your skin and is usually located on your hips, thighs, upper arms and buttocks. Pinchable fat at your belly is also subcutaneous. Your body uses some of this fat for energy, but it also acts as a layer of insulation to help regulate your body temperature.

A certain amount of stored body fat is required to help regulate your hormone production. Fat is particularly instrumental in the production of sex hormones, especially in women. Women who don't have enough body fat can experience a halt in their menstrual cycle.

Healthy Body Fat Levels

The average, healthy level of body fat is 15 to 20 percent for a man and 20 to 25 percent for a woman. Athletes and fitness enthusiasts may have body fat percentages that are lower to support athletic performance. Body fat levels below 8 percent in a man or 14 percent in a woman afford no additional health benefits and could put these individuals at risk of being too lean. Having too little fat can result in menstrual cycle interruptions, greater susceptibility to illness and hormone dysfunction.

A body fat percentage of 20 or more for a man or 30 or more for a woman increases the risk of chronic disease, such as type-2 diabetes and cardiovascular disease. Even if a person falls into a normal weight range, if too much of that weight comes from fat tissue, he is still at risk for developing weight-related health issues.