A few decades ago, "fat" was practically considered a curse word — it wasn't considered "healthy" to eat or, indeed, to have anywhere on your body. Today, however, research has shown that "fat" isn't such a simple term — a person can have four different types of fats, in fact — and it's also not necessarily something to avoid.
Here, we'll explore the different types of body fat and how can they affect your health in positive and negative ways.
Is Body Fat Bad?
First things first: Not all body fat is harmful to your health. In addition to keeping you warm, the fat in your body stores important vitamins, such as vitamins A, E, D and K, which are essential for organ and tissue function. Fat can also store and help regulate hormones, such as estrogen, which protects bones and female reproductive organs.
Having enough fat is also important for healthy brain function, and it even plays a role in balancing your metabolism and blood sugar.
But experts say that body fat can be potentially harmful, depending on what type of fat it is and how that fat is stored in the body.
What Are the Four Fats?
There are four main types of fat in the body:
First, one harmful type of fat is called visceral fat (aka hard fat) which lies deep underneath our abdominal muscles, wrapped around the organs in our abdominal cavity.
According to Tom Rifai, MD, a board-certified physician who specializes in metabolic disorders, visceral fat is often caused by a diet high in saturated fat, trans fats, refined carbohydrates and alcohol. When visceral fat surrounds our organs it can cause "metabolic mayhem," Dr. Rifai says, by releasing harmful chemicals such as cytokines that generate inflammation and disrupt healthy organ function.
Because of this, visceral fat "substantially" increases the likelihood of diseases like cancer and dementia, while also increasing the risk for heart attacks and stroke. Indeed, according to a study in the November 2014 issue of JACC: Cardiovascular Imaging, researchers found that patients with high levels of visceral fat stores also tended to have high levels of calcification in their coronary arteries and a higher risk of metabolic syndrome, regardless of their body mass index, or BMI. Visceral fat is also thought to influence insulin production, which could lead to diabetes. In other words? The less visceral fat a person has, the better.
Read more: Why Hard Belly Fat Is More Dangerous Than Soft Fat
A less harmful type of fat is called subcutaneous fat, or soft fat, which sits directly under our skin and, where belly fat is concerned, outside of the abdominal wall.
While visceral fat can't be measured without special equipment, Bonnie Taub-Dix, RDN, CDN, says that subcutaneous fat is visible from the outside of a person's body and can be measured easily using skinfold calipers. Subcutaneous fat commonly appears around the waist, hips, thighs and bottom, and unlike visceral fat, it can actually have some benefits.
Studies, such as one in the October 2015 issue of Cardiovascular Diabetology, have shown that subcutaneous fat corresponds with a lower risk of atherosclerosis, which is a build-up of fats and cholesterol inside artery walls. Similarly, in the 2014 study from JACC: Cardiovascular Imaging, subjects with high levels of subcutaneous fat had a lesser likelihood of having calcium deposits in their coronary arteries.
Although too much subcutaneous fat can strain tendons and ligaments, between the types of abdominal fats we can have, subcutaneous fat is definitely healthier.
Dangerous visceral fat is often caused by a diet high in saturated fat, trans fats, refined carbohydrates and alcohol. Nixing these things from your diet may help decrease the amount of hard fat in your body.
So where do white fat and brown fat fit in? White fat, says Dr. Rifai, makes up the vast majority of the fat we have in our bodies and can either be subcutaneous or visceral, depending on where it's located. If white fat is in the abdominal cavity, for example, it's visceral — but white belly fat that happens to be outside of the abdominal muscles is subcutaneous.
The purpose of white fat is to store energy and vitamins.
Brown fat, on the other hand, "is usually in subcutaneous areas, such as in between the shoulder blades, above the collarbone, and along the length of the spinal cord," says Dr. Rifai. But because brown fat can also surround our kidneys, it can technically be considered a visceral fat as well.
Brown fat, named for its iron-based, brown-colored pigmentation, makes up very little of our total fat stores as adults, though it's plentiful in babies. This makes sense when you consider that, according to the National Institutes of Health, the purpose of brown fat is to burn energy to generate heat — in this way, newborns get added protection against hypothermia when they need it the most.
White fat can be either harmful or helpful, depending on where it's located, but brown fat is still more of a mystery to researchers, although it hasn't been linked to any serious health issues.
Even more of a mystery is the recently discovered beige fat. While not a whole lot is known about this type of fat, researchers seem to think it's linked to a healthy weight, and that it helps the body burn calories to generate heat, per Harvard Medical School.
What Is Deep Fat?
Deep fat is just another term for visceral fat, Dr. Rifai says, because visceral fat is located deep in the abdominal cavity.
Because of its location, doctors need a special imaging tool called a DEXA scanner to be able to see and measure visceral fat and calculate your risk for metabolic disorders. But for people who don't have access to a practitioner with a DEXA scanner, Dr. Rifai recommends measuring the circumference of your waist rather than consulting your BMI. According to the American Diabetes Association, a waist circumference of 90 centimeters for men and 80 for women indicates central obesity and a high level of visceral fat.
Read more: How to Estimate Your Body Fat Percentage
How Much Body Fat Should I Have?
While subcutaneous brown and white fats aren't nearly as dangerous as visceral fat, excess fat still puts people at risk of health conditions such as sleep apnea, osteoarthritis and high blood pressure, according to the National Institute of Diabetes and Digestive and Kidney Diseases.
In general, people should aim for a body composition of about 14 to 38 percent fat for women and 6 to 24 percent for men, which is considered a healthy range. However, there is no one universal standard for how much body fat a person should have, since exercise level and risk factors play into what amount of body fat is right for each person. If you're concerned about your body fat percentage, speak with your doctor or another qualified professional, such as a certified personal trainer or registered dietitian.