In the past decade, scientists have uncovered a wealth of knowledge about types of body fat. Like cholesterol, there are good and bad types. Just last year researchers discovered an alarming difference between brown, or "good," fat and the more predominant "bad" fat, which tends to be white or yellow and collects around the waistline. Brown fat, which actually has a brownish tint to it, is stored mostly around the neck and under the collarbone (so, to a large extent, it's invisible). This fat encourages the body to burn calories to generate body heat , and plays an important role in keeping infants warm (infants, as we all know, have fatty necks).
Until very recently we believed that this fat was either gone or no longer active by adulthood. Much to the contrary, it may have a huge role in our ability to stay lean as adults. These recent studies found that lean people have far more brown fat than overweight and obese people, especially among older folks. Unlike its bad-fat counterpart, brown fat burns far more calories and generates more body heat when people are in a cooler environment. Women are more likely to have it than men, and women's fat deposits are larger and more active.
For most of us, body fat has a bad reputation. From the dimply stuff that plagues women's thighs to the beer bellies that can pop out in middle-aged men, fat is typically something we agonize over, scorn, and try to exercise away. But for scientists, fat is intriguing and becoming more so every day. Fat is one of the most fascinating organs out there.
Fat has more functions in the body than we thought. Fat is known to have two main purposes. 1) Fat stores excess calories in a safe way so you can mobilize the fat stores when you're hungry. 2) Fat releases hormones that control metabolism. .But that's the broad brushstroke picture.
Brown fat has gotten a lot of buzz recently, with the discovery that it's not the mostly worthless fat scientists had thought. In recent studies, scientists have found that lean people tend to have more brown fat than overweight or obese people and that when stimulated it can burn calories. Scientists are eyeing it as a potential obesity treatment if they can figure out a way to increase a person's brown fat or stimulate existing brown fat.
It's known that children have more brown fat than adults, and it's what helps them keep warm. Brown fat stores decline in adults but still help with warmth. Brown fat is more active in people in colder months, leading to the idea of sleeping in chillier rooms to burn a few more calories.
Brown fat is now thought to be more like muscle than like white fat. When activated, brown fat burns white fat.
Although leaner adults have more brown fat than heavier people, even their brown fat cells are greatly outnumbered by white fat cells. "A 150-pound person might have 20 or 30 pounds of fat. They are only going to have 2 or 3 ounces of brown fat. But that 2 ounces if maximally stimulated, could burn off 300 to 500 calories a day, enough to lose up to a pound in a week.
You might give people a drug that increases brown fat
But even if the drug to stimulate brown fat pans out, it won't be a cure-all for weight issues. It may, however, help a person achieve more weight loss combined with a sound diet and exercise regimen.
White fat is much more plentiful than brown, experts agree. The job of white fat is to store energy and produce hormones that are then secreted into the bloodstream.
Small fat cells produce a "good guy" hormone called adiponectin, which makes the liver and muscles sensitive to the hormone insulin, in the process making us less susceptible to diabetes and heart disease. When people become fat, the production of adiponectin slows down or shuts down, setting them up for disease.
Subcutaneous fat is found directly under the skin. It's the fat that's measured using skin-fold calipers to estimate your total body fat. In terms of overall health, subcutaneous fat in the thighs and buttocks, for instance, may not be as bad and may have some potential benefits. It may not cause as many problems as other types of fat, specifically the deeper, visceral fat. But subcutaneous fat cells on the belly may be another story. There's emerging evidence that the danger of big bellies lies not only in the deep visceral fat but also the subcutaneous fat.
Visceral or "deep" fat wraps around the inner organs and spells trouble for your health. How do you know if you have it? "If you have a large waist or belly, of course you have visceral fat. Visceral fat drives up your risk for diabetes, heart disease, stroke, and even dementia.
Visceral fat is thought to play a larger role in insulin resistance, which boosts risk of diabetes than other fat. It's not clear why, but it could explain or partially explain why visceral fat is a health risk.
In a study the records of more than 6,500 members of Kaiser Permanente of Northern California, a large health maintenance organization, for an average of 36 years, from the time they were in their 40s until they were in their 70s. The records included details on height, weight, and belly diameter, a reflection of the amount of visceral fat. Those with the biggest bellies had a higher risk of dementia than those with smaller bellies. The link was true even for people with excess belly fat but overall of normal weight.
Why belly fat and dementia are linked could be that substances such as leptin, a hormone released by the belly fat, may have some adverse effect on the brain. Leptin plays a role in appetite regulation but also in learning and memory.
Belly fat has gotten a mostly deserved reputation as an unhealthy fat. Understand that belly fat is both visceral and subcutaneous. We don't have a perfect way yet to determine which [of belly fat] is subcutaneous or visceral, except by CT scan, but that's not cost-effective.
But if you've got an oversize belly, figuring out how much is visceral and how much is subcutaneous isn't as important as recognizing a big belly is unhealthy. How big is too big? Women with a waist circumference more than 35 inches and men with a waist circumference more than 40 inches are at increased disease risk.
Abdominal fat is viewed as a bigger health risk than hip or thigh fat, experts say and that could mean having a worse effect on insulin resistance, boosting the risk of diabetes, and a worse effect on blood lipids, boosting heart and stroke risks.
Thigh Fat, Buttocks Fat
While men tend to accumulate fat in the belly, it's no secret women, especially if "pear-shaped," accumulate it in their thighs and buttocks. Unsightliness aside, emerging evidence suggests that pear-shaped women are protected from metabolic disease compared to big-bellied people. Thigh fat and butt fat might be good, referring to that area's stores of subcutaneous fat. But the benefit of women being pear shaped may stop at menopause, when women tend to deposit more fat in the abdomen.
Weight Loss and Fat Loss
So when you lose weight, what kind or kinds of fat do you shed? "You're losing white fat. People tend to lose evenly all over. The results change a bit, however, if you add workouts to your calorie reduction. If you exercise plus diet you will tend to lose slightly more visceral fat from your belly."