From secreting hormones to regulating body temperature, fats play multiple essential roles. Therefore, striving to reduce body fat to very low levels may be harmful to health.
Fat has been viewed in a negative light for many years. Diet culture urges us to burn it, food companies promote low-fat products, and bodybuilding forums share tips on how to reach the lowest possible level of body fat.
All you have to do is browse social media for a moment to find tips on how to get a “shredded” body, a look characterized by extremely visible muscles.
This year, experts expressed concern about the re-emergence of the trend toward extreme thinness, a trend fueled in some cases by the great popularity of weight-loss medications.
Although the accumulation of excess fat raises health concerns and may lead to obesity, its levels falling below the normal limit is not good for us either. Many experts have confirmed to me that striving to get rid of fat may be harmful from both a biological and social standpoint.
“We have to accept and love our body fat, as it performs a very important biological function,” says Elif Oral, an endocrinologist and professor of medicine at the University of Michigan.
So, how much fat do we really need? Why is having a lower body fat percentage than the required level harmful to our health?
Why is body fat important?
In general, there are two different types of fat: dietary fat and body fat.
Dietary fats are those that you get through food, while body fats are a natural way to store energy that the body does not need at the moment.
When you eat a meal, the dietary fats, carbohydrates, and proteins in the food break down into simple building blocks that the body can use as a source of energy. Carbohydrates turn into glucose, proteins into amino acids, and fats into fatty acids.
If a person continues to eat more calories than he consumes, fat cells known as "adipocytes" store these excess nutrients in the form of fats, "lipids", which leads to the enlargement of the size of these cells.
However, we now realize that body fat is not just a static and inactive store, but is an active contributor to the regulation of body functions.
As in the story of “Goldilocks and the Three Bears,” our body works best when things are “just right and balanced.” Extreme deficiency, just like excess, is dangerous to our health.
“We can think of body fat as a specialized storehouse, absorbing nutrients when energy is abundant, and releasing them only when they are needed,” says Mikael Ryden, professor of clinical and experimental adipose tissue research at Karolinska Institutet in Sweden.
He adds that it is a system that helped our ancestors survive during periods of food scarcity.
Another important role is communication, as fat cells produce hormones that inform the rest of the body about available energy levels and how full we feel.
Oral explains that leptin is the most studied of these hormones, noting that “leptin sends a signal to the brain that there is a sufficient reserve of energy, which allows the brain to have a kind of relaxation.” This, in turn, makes room for the body to focus on important vital processes, such as reproduction and fighting infection.
In the absence of leptin, the brain begins to worry about the amount of energy available, which leads to a decline in the priority of basic vital functions.
Body fat also plays an important role in keeping the body warm. While white fat works to store excess energy, it also forms an insulating layer.
In contrast, brown and beige fat contain specialized cells that burn energy to produce heat, which helps the body maintain its temperature.
What happens when we have too little fat?
It is well known that excess body fat has negative health consequences, including increased risk of cardiovascular disease, type 2 diabetes, certain types of cancer, and degenerative arthritis (osteoarthritis). However, having very low fat levels is not a good thing either.
Jessica Maung, a researcher and graduate student specializing in metabolic diseases at the University of Michigan, explains that a drop in body fat to extremely low levels as a result of severe calorie restriction can have profound effects on our health and vital functions. “The lack of adipose tissue leads to dysfunction in our organs and the body,” she says.
When the body lacks adequate fat, it responds by trying to conserve energy, effectively putting itself into a "starvation"-like state.
The body's systems begin to stop working efficiently, including the immune system. In the absence of any remaining reserves, the body begins to break down muscle for energy, and bone building and repair processes stop.
This leads to frailty and an increased risk of fractures, according to Frederick Carby, professor of metabolic medicine at the University of Oxford.
“It's not a healthy condition,” Carby adds, especially since it leaves the body with no reserves to deal with severe infections or other medical emergencies.
A lack of body fat can also affect hormones and reproductive health. Men who become very thin as a result of not getting enough food for long periods may have lower testosterone levels, as well as energy levels and physical performance.
As for female athletes who have a very low percentage of body fat, they may suffer from irregular menstruation or stop it completely.
Numerous studies have shown that being overweight in middle and later life is associated with better chances of survival when developing serious diseases.
For example, although obese people are more likely to develop cardiovascular diseases, they are less likely to die from these diseases compared to lighter people with the same condition, a phenomenon known as the “obesity paradox.”
Having fat stores appears to help the body withstand serious heart attacks, strokes and other severe illnesses, according to Oral.
In extreme cases, severe lipid deficiency can lead to serious health consequences or even death. For example, anorexia nervosa can cause permanent organ damage or death.
How much fat do we really need?
It may be difficult to measure your body fat percentage yourself, and we will discuss this later. There is no unified global percentage that can be considered a goal for everyone, as needs differ from one person to another.
However, as a general indicator, the body fat percentage of healthy adult men typically ranges between 10 percent and 20 percent, while that of healthy adult women ranges between 20 percent and 29 percent. As for people who suffer from obesity, the percentage of fat in their bodies exceeds 30 percent.
Regarding the ideal ratio, Ryden says: “It is very difficult to determine an exact range, as this ratio may vary according to people, gender, and races.”
The percentage of body fat is usually lower in athletes.
As part of her research, Tamara Hugh Butler, a researcher specializing in sports performance at Wayne State University in Detroit, and her team conducted examinations of more than 700 athletes using the DEXA device, which is a device that measures body composition, including internal fat.
The researcher says: “The lowest percentage of fat we observed in athletes was 10 percent for men and 16 percent for women.”
She adds that some participants were surprised by these results, given that the athletes in the study were training regularly, and they believed that the percentage of fat in their bodies was very low, ranging between only 1 percent and 2 percent.
The location of fat storage in the body also plays an important role, as visceral fat, also known as belly fat, is extremely harmful when accumulated in large quantities.
Unlike subcutaneous fat, visceral fat surrounds vital internal organs and secretes inflammatory chemicals, which leads to high blood pressure, interference with insulin action, difficulty in controlling blood sugar levels, and increases the risk of developing type 2 diabetes.
How do we measure fat percentage?
There are several ways to measure the amount of body fat.
Whole-body DEXA scans are the most accurate and detailed methods, as they can distinguish between body fat, lean muscle mass, and bone mass. However, these tests require specialized equipment and may be expensive.
A common home test is the “skinfold” test, in which the thickness of the layer of fat located directly under the skin is measured by pinching it using a measuring tool (special forceps) designed specifically for this purpose.
However, this tool only measures the thickness of fat folds in specific areas of the body, and cannot directly measure visceral fat.
Another option for home use is smart scales.
These devices work by passing a weak electrical current through the body to estimate fat mass, but the readings are affected by the level of fluids in the body, so they are not accurate for measuring fat levels. It also does not explain where fat is stored in the body, and does not distinguish between visceral fat and other types of fat.
Once you measure your waist circumference, you can use a calculator to determine this ratio, noting that a healthy range is usually between 0.4 and 0.49.
The "waist to hip ratio" can also give a good indicator. To obtain this ratio, measure the waist circumference at the level of the navel and divide this value by the measurement of the widest part of the hips.
A ratio exceeding 0.90 for men and 0.85 for women is considered high, as excess fat around the waist indicates poor metabolic health.
It is worth noting that the body mass index (BMI) is not an accurate measure of body fat, because it does not distinguish between fat and muscle mass. People who have a large muscle mass and a very low percentage of fat may have a high BMI.
You may want to pay more attention to your body composition as we age, as our fat mass tends to increase while muscle and bone levels decrease.
Since this may lead to negative health effects, it is important to follow a good diet and exercise, including strength training.
However, we should recognize the importance of the vital functions that fat performs in our bodies, and not be overly preoccupied with extreme fat goals.
The most important thing is to maintain the appropriate amount, rather than striving to reduce it to the minimum possible. Or as Oral says: “We believe that fat is both powerful and beautiful.”
