What is a healthy body fat percentage range, and what happens if it falls below that?

Doctor's Answers 1

What is fat?

The scientific term for body fat is "adipose tissue." Adipose tissue serves a number of important functions. Its primary purpose is to store lipids from which the body creates energy. In addition, it secretes a number of important hormones and provides the body with some cushioning as well as insulation.

All our body cells have membranes made from fats. And many substances such as hormones are also made from fats, so we need the right kind of fats and oils from our foods. These come from oily fish, and also from nuts, seed oils, and olive oil. A healthy way is to use olive oil, nut oils and rapeseed oil for cooking, dressings, and sauces. Fat-soluble vitamins are present in the fatty elements of foods such as cheese, eggs, milk, butter and spreads, oily fish, nuts and seeds.

How much fat is healthy?

Body fat includes essential body fat and storage body fat. Essential body fat is a base level of fat that is found in most parts of the body. It is necessary fat that maintains life and reproductive functions. The amount of essential fat differs between men and women and is typically around 2-5% in men, and 10-13% in women. The healthy range of body fat for men is typically defined as 8-19%, while the healthy range for women is 21-33%.

You need to have at least a certain amount of fat in your body for good health, which varies based on your gender. Some athletes have body fat percentages between 14-20%, and 21-24% is common in fit people. The average woman, however, has between 25-31% of fat.

For men, essential fat levels are between 2-5%, with male athletes often having levels from 6-13%. A fit man might have a body fat percentage between 14-17%, while the average man ranges from 18-24% fat.

What if I have too little fat?

Reasons 1-4: Fat-soluble vitamins, disease risk, fertility, and energy level

The following are possible consequences of low body fat percentage:

First, there could be deficiencies of the fat-soluble vitamins -- A, D, E and K -- as they can only be absorbed by one’s body in the presence of fat. A deficiency of vitamin A can interfere with our vision or cause our skin to be very dry, and it can also decrease immune function and make illness more likely. Not getting enough vitamin D causes our bones to become weak, and an insufficient intake of vitamin K can cause the blood to not clot properly.

Second, there are increased risks of diseases. Having too little body fat may increase our risk of heart disease, gastrointestinal problems, and damage to our nervous system. An extremely low body fat percentage can stir up the normal functions of the cardiovascular system. When bodybuilders prepared for competition by additionally lowering their body fat, their heart rate dropped to 27 beats per minute. Such a condition is called bradycardia and can lead to vertigo, fainting, or even worse – cardiac arrest. Very low lipid index can make electrolyte imbalances, and low-caloric intakes can be the cause of arrhythmia or sudden cardiac death.

There is also a risk of organ shrinkage. Because a very low body fat percentage can affect one’s immune system, one is more likely to suffer from infectious diseases as well. Limited fat stores may affect one’s ability to use insulin, making one more likely to develop diabetes.

The third issue pertains to fertility. 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% 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. This is a very likely outcome for women.

Men too can experience bad aftermaths from having too low body fat index. Males can have their testosterone levels dropped, and this leads to loss of sexual desire, low production and low quality of sperm, as well as problems in accumulating lean muscle tissue.

The fourth concern is related to our energy level. Being extremely thin can also cause problems with our metabolism, decrease our brain function and cause fatigue. If one does not have a lot of fat and is not consuming enough calories, one’s body will start to break down muscle for energy, making one weaker overall. When one is deprived of too much fat, one does not have energy reserves. His body will not be able to function properly, as it requires sufficient energy to do so. A too low fat index is connected to thyroid dysfunction and slow heart rate.

Reasons 5-8: Food cravings, muscle loss, feeling cold, and a weaker immune system

Fifth, one develops nagging food cravings. When one is dieting and has low body adiposity, circulating levels of the hormone leptin start to decrease drastically. Leptin receptors, located in the hypothalamus in the brain, react to this drop by enhancing appetite. This leads to one feeling hungry almost all the time.

Sixth, muscle gain becomes nearly impossible and muscles get weaker. When body fat is too low, testosterone levels drop critically, muscles become weaker and recover slowly. Bodybuilders who wanted to significantly drop their body fat also had their body mass and strength dropped too, months before a bodybuilding competition. It took them more than half a year to regain the lost muscle.

Seventh, one feels cold. Since body fat has a role in maintaining body temperature and insulating the organs, those with low body fat index often complain about being cold. The internal temperature can also be unbalanced due to thyroid dysfunctions.

Eighth, immune system grows weaker. Very low energy intake and body fat are linked to higher cortisol levels which tamper with the immune system. This tremendously increases one’s risk of getting an infection.

Reasons 9-11: Mood swings, brain fog, and social problems

Ninth, one can experience severe mood swings. Sufficient essential fatty acids in the brain are required for proper neurologic functions, brain development, and overall brain health.

Tenth, having brain fog. Omega fats are vital for normal brain functions, and if the brain does not receive enough of them, one will experience bad concentration, mental fatigue, and slow thinking.

Eleventh, problems with social life. Having too low body fat index requires certain lifestyle changes. For instance, one has to decrease alcohol intake and observe one’s diet strictly.

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