The Two Types of Fat -- Visceral and Subcutaneous
and Which Poses the Greatest Risk to You
© 2014 Health Realizations, Inc.
It's the dreaded "F-word" -- FAT. Many of us are consumed with it ... gaining it, fearing it and doing just about anything to get rid of it. Yet we all have it. Even lean adults have 40 billion fat cells; those who are obese may have 80 billion to 120 billion. But it's not only the amount of fat that makes the difference between being healthy and unhealthy, it's the type of fat, and where it's distributed in your body.
People with large bellies are at a higher risk of dangerous visceral fat, but thin people, particularly those who lead sedentary lifestyles, are also at risk.
Visceral Fat Vs. Subcutaneous Fat
There are two types of fat: subcutaneous and visceral. Subcutaneous fat is the type found just underneath the skin, which may cause dimpling and cellulite. Visceral fat, on the other hand, is located in the abdomen and surrounding vital organs. It can infiltrate the liver and other organs, streak through your muscles and even strangle your heart; and you can have it even if you appear to be thin.
It is the latter, visceral, fat that is linked to everything from bad cholesterol and hypertension to diabetes, heart disease and stroke.
While you can spot visceral fat if you have a protruding "beer" belly, it's not always that simple. Only a high-tech MRI (magnetic resonance imaging) can really show the body's fat composition, and researchers are finding that thin people may also have high amounts of this internal fat. They've even developed a tongue-in-cheek name for them: Tofi (Thin on the Outside, Fat on the Inside).
'"We've even scanned people who are underweight and found up to seven liters of fat inside them," said Professor Jimmy Bell, head of the molecular imaging group at the Medical Research Council's center at Imperial College in the UK.
Looks Can be Deceiving
While commonsense would dictate that Japanese sumo wrestlers, who eat upwards of 5,000 calories a day and are obese by most weight standards, are setting themselves up for a barrage of obesity-related health problems, studies have found that this is not the case. Why? MRIs of sumo wrestlers have shown they have hardly any internal fat.
"They have low cholesterol, they have low insulin resistance and a low level of triglycerides," said Bell. "Their fat is all stored under the skin, on the outside."
Meanwhile, someone who appears thin on the outside, yet doesn't exercise nearly as much as a sumo wrestler, may be at risk of a host of health problems because their fat is being stored on the inside, and in the organs.
"This is particularly true of men who have a slim build but who do little or no exercise," Bell said. "We know now that 40 percent of people have fat infiltration of the liver, which is linked to so many other health problems."
Is Fat Really an Organ?
While once considered an inert storage system, researchers now know that fat cells are actually incredibly dynamic and intelligent.
"They were always thought to be poor, dumb sacks of lard," said Roger Unger, an obesity researcher at the University of Texas Southwestern Medical Center. "It turns out that they end up being very talented, very versatile, very important players."
Fat cells not only produce chemicals and hormones but they also send out signals that affect everything from our brain, liver, muscles and immune system to our mood and ability to reproduce.
"In the old days, people used to think fat tissue was a passive organ," said Rexford S. Ahima, an endocrinologist at the University of Pennsylvania. "Now it's obvious that it makes and secretes more hormones and proteins than probably any other. It's at the center of a very complex system. It coordinates how much we eat, how much energy we burn, how the immune system works, how we reproduce. The list goes on."
Jogging 17 miles a week for eight months can produce significant decreases in visceral fat, according to a Duke University study.
Do Genetics Play a Role in Visceral Fat?
Genetic factors do appear to play a role in fat storage and body shape.
"Our work so far has shown that you can take two men of the same age, with the same BMI [body mass index], and find one with five liters of fat within him and another with two liters," said Bell.
Body shape also affects a person's risk of carrying visceral fat, with those shaped like apples (who carry weight around their abdomen) at a higher risk than those shaped like pears (who carry fat around their hips, thighs and bottom).
Want to Get Rid of Visceral Fat? (Crash Dieting is NOT the Answer)
You may be tempted after reading this article to go on a crash diet to lose visceral fat, but this is not a wise choice. In fact, studies suggest that "yo-yo" dieting (constantly losing, then regaining, weight) may encourage visceral fat.
"Over the past five years, we've demonized fat and become obsessed with obesity, which is mostly talked about in terms of weight loss. But what matters is where it is distributed. As you lose weight, it tends to go from the top and bottom of your body first, so it can become concentrated in the abdomen. That is the most dangerous zone of all, and it's possible that going on a constant series of diets actually encourages the storage of fat in this region."
What can you do to lose visceral fat? Exercise. A study by Duke University Medical Center researchers found that people who were physically inactive had significant increases in visceral fat, while those who exercised frequently had significant decreases in visceral fat, over an eight-month period. The study found:
Those who did not exercise had an 8.6 percent increase in visceral fat.
Those who exercised the highest amount (17 miles of jogging per week) had an 8.1 percent decrease in visceral fat.
Those who exercised a low amount (11 miles of jogging each week) did not significantly increase or decrease visceral fat.
"The results of our investigation show that in sedentary overweight adults who continue to choose a sedentary lifestyle the detrimental effects are worse and more rapid than we previously thought," said Cris Slentz, Ph.D., who led the study.
"On the other hand, participants who exercised at a level equivalent to 17 miles of jogging each week saw significant declines in visceral fat, subcutaneous abdominal fat and total abdominal fat," he said. "While this may seem like a lot of exercise, our previously sedentary and overweight subjects were quite capable of doing this amount."
"We also found that a modest exercise program equivalent to a brisk 30-minute walk six times a week can prevent accumulation of visceral fat, while even more exercise can actually reverse the amount of visceral fat," Slentz said.
Duke University Medical Center
Journal of Applied Physiology, 99(4):1613-8