Although it's more common in the United States to have too much body fat than too little, make sure you don't go too far in your weight-loss efforts. If your body fat drops too low, it can have health consequences, just as when your body fat is too high. To get a more personalized assessment of your current health, speak with your doctor if you're concerned that you may be too slim.
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Essential Fat Levels
You need to have at least a certain amount of fat in your body for good health, which varies based on your gender. If you're a woman, you need at least 10 to 13 percent body fat. Some athletes have body fat percentages between 14 and 20 percent, and 21 to 24 percent is common in fit people. The average woman, however, has between 25 and 31 percent. More than that is considered considered too high.
For men, essential fat levels are between 2 and 5 percent, with male athletes often having levels from 6 to 13 percent. A fit man might have a body fat percentage between 14 and 17 percent, while the average man ranges from 18 to 24 percent fat. Having more than that can have adverse health effects and isn't recommended.
Fat-Soluble Vitamin Deficiencies
To maintain a very low body fat percentage, you usually can't eat much fat. Doing so could lead to deficiencies of the fat-soluble vitamins -- A, D, E and K -- as they can only be absorbed by your body in the presence of fat. A deficiency of vitamin A can interfere with your vision or cause your skin to be very dry, and it can also decrease immune function and make illness more likely. Not getting enough vitamin D causes your bones to become weak, and an insufficient intake of vitamin K can cause your blood to not clot properly.
Increased Disease Risk
Body fat is important for a wide variety of body functions. Having too little body fat may increase your risk for heart disease, gastrointestinal problems and damage to your nervous system, Also, the University of Pennsylvania adds, you incur the risk of organ shrinkage. Because a very low body fat percentage can affect your immune system, you are more likely to experience infectious diseases as well. Limited fat stores may affect your body's ability to use insulin, making you more likely to develop diabetes.
If you're a woman with a low body fat percentage, you may not be able to become pregnant, even if you have more than the amount of fat considered essential. You may need as much as 22 percent body fat to have regular menstrual cycles and become pregnant. Should your body fat decrease too much while you're pregnant, you may not be able to sustain the pregnancy.
Other Potential Effects of Low Body Fat
Being extremely thin can also cause problems with your metabolism, decrease your brain function and cause fatigue. Body fat helps keep you warm when it's cold, and without fat to help hold it up, your skin may sag and start to look wrinkled, making you look older than you are. If you don't have a lot of fat and aren't consuming enough calories, your body will start to break down muscle for energy, making you weaker overall. Eventually, if you don't start to eat and drink more to increase your body fat levels, you could become too dehydrated or starve to death, although starvation is uncommon in the United States.
- American Council on Exercise: What Are the Guidelines for Percentage of Body Fat Loss?
- University of Nevada Cooperative Extension: Weighing in on Body Fat
- PennRec: Body Composition Information and FAQ’s Sheet
- Go Ask Alice!: What Does Body Fat Percentage Mean?
- Colorado State University Extension: Fat-Soluble Vitamins: A, D, E, and K
- The New York Times: Too Little Fat Can Be As Bad As Too Much