Keeping your fat intake in check helps you stay healthy, but avoiding fat altogether can do serious harm to your body. Eating no fat can disrupt your hormone levels, weaken your bones and impair your digestion, kidney function and immune function. In severe cases of fat deficiency, organ failure and death result. Because even a very low-fat diet may undermine your health, it's important to include a moderate amount of fat in your meal plan.
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Fat-Soluble Vitamin Deficiency
Without enough fat in your diet, you may have trouble obtaining and absorbing the fat-soluble vitamins A, D, E and K. Lack of vitamin A can lead to night blindness and eventually compete blindness, while too little vitamin K may cause poor blood clotting. Severe lack of vitamin D may lead to the bone-softening diseases rickets in children and osteomalacia in adults. While vitamin E deficiency is extremely rare, it can lead to muscle weakness and vision problems. Less than optimal levels of fat-soluble vitamins can also leave you with severely dry skin, eczema and other skin conditions.
Essential Fatty Acid Deficiency
Essential fatty acids, or EFAs, are fats your body requires for health but can't produce on its own, meaning you need to get them from your diet. These are fats alpha-linolenic acid, or ALA, and linoleic acid, or LA. Your body uses EFAs to produce hormone-like substances that help control certain physical processes, including kidney and gastrointestinal function, immune function and blood pressure. Low intake of omega-3 fatty acids, a group that includes alpha-linolenic acid, is among the leading preventable causes of death in the United States, determined a Harvard School of Public Health study published in "Public Library of Science Medicine" in April 2009.
A diet devoid of fat or too low in fat can disrupt your levels of estrogen and testosterone, warn experts from Columbia University's Go Ask Alice! service. In women, this may alter the menstrual cycle and undermine bone health. Estrogen supports bone health by aiding calcium absorption and inhibiting the breakdown of bones, protecting them from osteoporosis. In men, low testosterone levels can interfere with the ability to increase muscle strength and size.
Getting Enough Healthy Fats
Ideally, you should get around 20 to 35 percent of your total daily calories from fat. One gram of fat provides 9 calories, so if you need 2,000 calories daily, you'll need 44 to 78 g of fat a day. At minimum, you'll need at least 10 of your total calories from fat, according to United Nations Food and Agriculture Organization experts; but because this is less than optimal, avoid reducing your fat intake this low without consulting a health care provider. When choosing fat sources, focus on monounsaturated fat and polyunsaturated fat from sources like vegetable oils, nuts, seeds and avocados; and include omega-3 fatty acids as found in sources like fish and walnuts. Limit saturated fat, found in foods like meats, cheese and butter, to 10 percent of your total fat intake, and avoid trans fats often found in margarine and commercial baked goods.