Fat and obesity have been getting a lot of press lately. Fat friends beget other fat friends, and while obesity is definitely on the rise (I’ll post more about that later…) fat is getting a bum rap.
From the New York Times:
By NATALIE ANGIER
Published: August 7, 2007
In this country, the most popular cosmetic surgery procedure is liposuction: doctors vacuum out something like two million pounds of fat from the thighs, bellies, buttocks, jowls and man-breasts of 325,000 people a year. What happens to all that extracted adipose tissue? It’s bagged and disposed of as medical waste; or maybe, given the recent news about socially contagious fat, it’s sent by FedEx to the patients’ old college chums. But one thing the fat surely is not, and that is given due thanks for serving as scapegoat, and for a job well done.
We are now in what feels like the 347th year of the fastidiously vilified “obesity epidemic.” Health officials repeatedly warn that everywhere in the world people are gaining too much weight and putting themselves at risk of diabetes, high blood pressure, heart disease and other obesity-linked illnesses, not to mention taking up more than their fair share of molded plastic subway seat.
It’s easy to fear and despise our body fat and to see it as an unnatural, inert, pointless counterpoint to all things phat and fabulous. Yet fat tissue is not the problem here, and to castigate fat for getting too big and to blame it for high blood pressure or a wheezing heart is like a heavy drinker blaming the liver for turning cirrhotic. Just as the lush’s liver was merely doing its hepatic best to detoxify the large quantities of liquor in which it was doused, and just as the alcoholic would have been far worse off had the liver not been playing Hepa-filter in the first place, so our fat tissue, by efficiently absorbing the excess packets of energy we put in our mouths, has our best interests at heart.
“Obesity is not due to any defect in adipose tissue per se; it’s an issue of energy balance,” said Bruce M. Spiegelman of the Dana-Farber Cancer Institute in Boston. If you are consuming too many calories relative to what you burn off, the body must cope with that energy surplus, he said, “and adipose tissue is the proper place for it.”
“If you had no fat cells, no adipose tissue, you’d still be out of energy balance, and you’d put the excess energy somewhere else,” he said, at which point really bad things can happen. Consider the lipodystrophy diseases, rare metabolic disorders in which the body lacks fat tissue and instead dumps its energy overruns in that jack-of-all-organs, the liver, causing extreme liver swelling, liver failure and sometimes liver-bearer death.
“Some adipose tissue is a good thing,” said Barbara Kahn, chief of the endocrinology, diabetes and metabolism division at Beth Israel Deaconess Medical Center, at Harvard.
Indeed, evolutionary biologists have proposed that our relative plumpness compared with our closest nonhuman kin, the chimpanzee, may help explain our relative braininess. Even a lean male athlete with a body fat content of 8 percent to 10 percent of total body mass (half the fat found on the average nonobese, non-Olympic American man) is still a few percentage points more marbled than a wild male chimpanzee, and scientists have suggested that our distinctive adipose stores help ensure that our big brains will be fed even when our cupboards go bare.
Scientists who study fat emphasize that its bland and amorphous appearance notwithstanding, our adipose depots represent highly specialized organs, as finely honed to the task of energy storage as muscle is built for flexing. Our body fat is made of some 40 billion fat cells, or adipocytes, and their supportive matrix, with most of the bulk stashed under the skin but also threaded viscerally, around and between other organs. Each fat cell is essentially a bouncing balloon filled with those greasy lipids we call triglycerides, three fatty acid chains of mostly carbons and hydrogens arrayed in high-energy configurations that explain why, gram for gram, dietary fat has more than twice the calories of meat or starch; and every fatty acid trio is tacked to a sugar-sweet glycerol frame.
In most body cells, the watery cytoplasm where the labor of proteins takes place accounts for maybe 70 percent of the cell’s volume, with another 10 percent given over to the nucleus, seat of the cell’s DNA. In a fat cell, by contrast, lipids are king, queen and bishop, and the checkerboard, too. They fill more than 95 percent of the adipocyte volume, crowding the cytoplasm with its proteins and the nucleus with its genes up against the cell wall in what Dr. Kahn calls “a crescent moon space.”
Yet for all its lipid density, the average fat cell is ever primed to hoard more, to take in more fatty acids and sugars from the blood and stitch them into triglyceride stores, and to swell to several times its cellular waistline of yore. Most weight that we gain and lose in life is the result of our existing fat cells growing and shrinking, absorbing and releasing energy-rich lipids as needed, depending on our diet and exercise regimens of the moment. But when exposed to chronic caloric overload, fat cells will initiate cell division to augment the supply; and because fat cells, like muscle cells, rarely turn over and die, those new lipidinous recruits will be your helpmeets for life.
Fat is no rutabaga. It is dynamic and mercantile, exchanging chemical signals with the brain, bones, gonads and immune system, and with every energy manager on the body’s long alimentary train.
“We used to think of an adipose cell as an inert storage depot,” Dr. Kahn said. “Now we appreciate that it is an endocrine organ,” in other words, an organ that like the thyroid or pancreas, secretes hormones to shape the behavior of other tissues far and wide. Squashed to the side a fat cell’s cytoplasm may be, but it nevertheless spins out a steady supply of at least 20 different hormones. Key among them is leptin, an essential player in reproduction. Scientists suspect that a girl enters puberty when her fat stores become sufficiently dense to begin releasing leptin, which signals the brain to set the pulsing axis of gonadal hormones in motion.
Fat also seems to know when it is getting out of hand, and it may resist new personal growth. Dr. Spiegelman and others have shown that with the onset of obesity — defined as 25 or more pounds above one’s ideal weight — the fat tissue starts releasing potent inflammatory hormones. That response is complex and harmful in the long run. But in the short term, said Dr. Spiegelman, “inflammation clearly has an anti-obesity effect, and it may be the body’s attempt to restrain further accumulation of adipose tissue.” The fat sizes up the risks and benefits, and it takes its fat chance.