What does body fat percentage mean?

Dear Alice,

I'm a vegetarian with 'wanna-be vegan tendencies' (i.e., I don't eat eggs or milk as a substance itself, but do it 'hidden' in other foods, like bread, pasta, etc.)

I've been advised by my fitness instructor that my 'body fat' percentage is too low, and I need to consider eating oily fish, milk, eggs, etc. in order to gain weight.

A strict vegan friend of mine has just suggested that I eat extra nuts, rice, and veg, and the extra calories will be converted to fat if I don't 'use them up,' but I'm not convinced. As a woman, I'm sure I need 'fats,' but how to get them when my choices seem limited?

Also, could you explain 'body fat percentage,' and what is safe and unsafe?

Thanks, Alice.

Dear Reader, 

Body fat is indeed essential to normal body functioning, and you may be surprised to learn that your choices for increasing fat aren't as limited as you may think, even considering your "wanna-be-vegan tendencies." Body fat plays important roles in your body: it stores energy for you to use between eating; releases hormones which regulate your metabolism, appetite, and insulin sensitivity; and releases proteins for the immune system. Fat cells (also known as adipocytes) are the main storage sites for energy in the body. They express and secrete endocrine hormones, which send messages to tissue cells and organs throughout the body. Body fat percentage indicates how much of your total body composition is fat. The designation of healthy or unhealthy is determined by your body and its needs. Too low a body fat percentage results in disrupted metabolism, fatigue, and lowered cognitive function, among other things. Read on for more! 

In most people, about 90 percent of body fat is subcutaneous, meaning it's found right under your skin. The other ten percent is visceral fat, which is under the abdominal wall, in the space around the liver and intestines, and in the omentum—a multilayered fold of fatty tissue that supports abdominal structures. In people who menstruate, visceral fat tends to sit around the waist during middle years, or after menopause. When in excess, visceral fat has been associated with cardiovascular disease, dementia, asthma, breast cancer, and colorectal cancer. People who menstruate with body fat lower than between 10 and 22 percent may develop amenorrhea (absence of menstrual periods), because the body senses inadequate energy reserves or high physical stress—this may also impact pregnancy. There are many different ways to measure body fat, and these can vary in accuracy, cost, and complexity. Some of those ways include: 

  • Skinfold calipers pinch your skin to measure its thickness in millimeters, assessing your subcutaneous fat. These calipers are specially designed and calibrated, and even when used by someone with substantial training, can still have a high error rate. 
  • Body measurements such as waist and neck circumference can be used to measure body fat. Waist circumference approximates your body make-up by calculating your waist-to-hip ratio (WHR) or waist-to-height ratio (WHtR), which is slightly different from the body mass index (BMI). Neck circumference (NC) is also a screening measure for body fat value. 
  • Hydrostatic weighing—also known as underwater weighing—is one of the most accurate methods of measuring body composition but is inaccessible to most people because it’s very expensive and requires special equipment and personnel training. 
  • Air-displacement plethysmography is similar to hydrostatic weighing, but it replaces water with air and has a similar accuracy and much lower cost than hydrostatic weighing. 
  • Bioelectrical impedance assesses how electrical currents flow through your body to determine body fat percentage, and while this can be low-cost and easy to use at home, these devices can also have error rates over ten percent. 
  • Three-dimensional (3-D) body scans are a newer technology that use laser capture technology to assess body composition. 
  • Dual energy x-ray absorptiometry (DEXA) uses x-rays that measure variations in tissue density to assess body composition. 

In terms of ways to increase body fat, you can do so by taking in more calories than you expend, eating regularly, and eating more proteins, carbohydrates, and fats. Fat-soluble vitamins such as vitamins A, D, E, and K and phytochemicals—compounds produced by plants—are essential to maintaining health. Your vegan friend suggested high fat foods because they provide more calories for a smaller amount of food than low fat foods. Plant-based foods such as vegetables, legumes, fruits, whole grains, nuts, and seeds provide a solid framework for managing your caloric intake. A good rule of thumb is that about 25 to 35 percent of your total caloric intake should be from fats, and at most five to six percent of your daily caloric intake should be from saturated fats

Although saturated fats are often found in meat, eggs, and dairy, there are a few plant-based foods, such as coconuts, which contain high levels of saturated fats and can support your vegan-leaning diet. If you're looking to eat more unsaturated fat, healthier fat source options to consider are monosaturated and polysaturated fats, both of which have a variety of plant-based food options to choose from. As you navigate different types of foods to support your dietary needs, consider discussing nutritional options with a dietitian or a health care provider for additional support. 

Hope this helps you understand your body a little better. 

Last updated May 26, 2023
Originally published Apr 25, 2003

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