The patient was neither obese enough nor desperate enough for stomach-stapling surgery. But he had raging diabetes and a daunting load of the most dangerous fat: the visceral kind that surrounds internal organs and swells pot bellies, inviting heart disease and stroke.
So he chose to undergo an experimental operation based on a radical proposition: that simply slicing out a hefty chunk of his visceral fat, by removing a curtainlike ﬂap of internal abdominal fat called the omentum, might help with his diabetes and other health problems. Unlike liposuction, which sucks out fat just under the skin, the omentum operation has no cosmetic effect, and is not aimed at weight loss. Rather, it reﬂects a mounting push among researchers around the world to understand and neutralize visceral fat, now that a growing body of data is showing that it is more harmful than fat near the surface.
Beth Israel Deaconess Medical Center surgeons, working with obesity specialists at Joslin Diabetes Center, have tried the experimental surgery on four patients in recent months, using a two-hour laparoscopic procedure that involves pulling strips of the yellow abdominal fat out through tiny holes. Their study, still underway, is the ﬁrst to examine the possible health beneﬁts of removing only the omentum.
Excess fat is the major cause of Type 2, or adult onset, diabetes, which affects about 17 million Americans, more than twice as many as in 1980. If the experiment pans out, it could conceivably give these multiplying millions a one-time surgical solution to replace a lifetime of medication, said Dr. Edward Mun, director of bariatric surgery at Beth Israel Deaconess and the studys leader. But I think thats a real long shot, and I dont want to speculate that far off, he said.
Doctors have known for decades that top-heavy people nicknamed apples tend to be at greater risk for heart problems and other ills associated with obesity than bottom-heavy people, who are known as pears. But over the last several years, a spurt of research has built an ever-stronger case against visceral fat, to the point that we believe that this hidden fat is the most dangerous fat in our body, said Dr. Osama Hamdy, director of the Visceral fat obesity clinic at the Joslin.
The amount of fat that people accumulate in the central abdominal area is the best correlation to obesity side effects including diabetes, high blood pressure, heart disease, and high cholesterol, he said.
One of the best ways to detect visceral fat turns out to be the simple tape measure. Men with waists over 40 inches, and women with waists over 35 inches, are likeliest to have problems. Interestingly, the average American waist has gone up by about 1 inch over the last six years, Hamdy added ominously.
Exercise and weight loss are known to help reduce visceral fat, Hamdy said. But otherwise, there is no established medical strategy for ﬁghting it, he and others said; and except for the omentum, which is relatively free-hanging and makes up roughly one-third of a persons visceral fat, most of it is in hard-to-get-at spots that do not lend themselves to the scalpel. Surgery to reduce visceral fat has been tried in rodents, however, and studies have indicated that when it is cut out, the animals diabetes improves, the researchers said.
In humans, the most intriguing clues come from gastric bypass surgery: after having the operation, which reduces the patients stomach to a small pouch, most patients with Type 2 diabetes have been cured. The reason is unclear, but the operation does reconﬁgure the digestive system to bypass areas heavy on visceral fat. The cure usually comes so quickly that it cannot be attributed to weight loss.
And a 2002 Swedish study indicated that among 50 patients who underwent gastric banding surgery, which also limits the stomach, the half who also had their omentum removed showed much more improvement in their blood sugar readings than those who only had the basic operation. Gastric bypass surgery is radical and a bit risky, however, and is generally approved only for patients who are more than 100 pounds overweight.
The omentum operation could eventually offer a less radical alternative for people who would not qualify for gastric bypass, said Dr. Justin Maykel of Beth Israel Deaconess, who initiated the omentum study.
It has been enrolling diabetic patients with a body mass index between 30 and 40 for someone 5 foot 8, that would translate to a weight between 197 and 262 pounds and who have heavy visceral fat, as revealed in a CAT scan. The study will track everything from blood sugar levels, an indicator of diabetes, to fat-related hormones in patients, and the researchers hope it will advance basic understanding of visceral fat.
It is increasingly clear, they say, that such fat is not a passive repository of energy, but rather functions as an active organ that emits hormones and other chemicals, some of them harmful. Visceral fat appears to be more metabolically active than surface fat, but much of how it works remains mysterious. The researchers are seeking a total of six patients for this initial pilot study, but they hope the results will be promising enough that they can undertake a larger, longer study to test the operation. The results of the current study have not been analyzed yet and any conclusions are months away, said Maykel.
The researchers believe, he said, that any decrease in the volume of visceral fat should bring beneﬁts. The question is, what beneﬁt, what degree of beneﬁt, and what will be the long-term impacts? he said. It may be the wrong area of visceral fat or not enough thats what makes science interesting.
Obesity researchers unconnected with the omentum experiment offered mixed assessments of its chances.
Dr. Walter J. Pories, a professor at East Carolina University and a gastric bypass surgery pioneer, said he believed the omentum operation would prove an important piece of work in terms of advancing the understanding of how fat acts on an individuals metabolism.
As for the diabetic patients, My guess, and its a straight guess, is that their insulin resistance meaning their bodies do not properly respond to insulin will diminish and that the patients will do better, he said. Of course, the question is, How much?
Dr. Nir Barzilai, director of the Institute for Aging Research at Albert Einstein College of Medicine in New York, sounded more skeptical, though certainly intrigued. I do have a lot of questions, he said.
One of them is, Can they take enough fat to make an impact? said Barzilai. His work in aging rats has shown that removing large amounts of their visceral fat could prevent the rats from developing diabetes, but, he cautioned, The fat in rats and the fat in humans is not in the same place.
The patient with raging diabetes who underwent the operation said his blood sugar fell dramatically as a result and has remained lower, but he has gained back most of the 20 pounds or so he lost in the weeks following the surgery. A 52-year-old Boston Web producer, he asked to remain anonymous to keep his medical details private.
The operation went uneventfully, and he recovered fully within days; there have been no complications with any of the four patients, Mun, the study leader, said. But, the patient said, Its not a panacea, unfortunately. These days, he is taking drugs for lingering diabetes, high cholesterol, and appetite control, but still carrying about 215 pounds on his 5-foot-7-inch frame.
I think the jury is out in terms of the long-term beneﬁts, he said. But one thing is clear to him, he said: I dont think theres an easy way around this. We as a society have to eat differently, eat less, and get off our butts.
Carey Goldberg is reachable at firstname.lastname@example.org.
Q. Who should worry?
A. Men with waists over 40 inches and women with waists over 35 inches are considered at particular risk, but even people with seemingly healthy weights may have a problem.
Q. How can you tell if its a problem?
A. One telltale sign of visceral fat is that it tends to make a belly feel ﬁrm, rather than ﬂabby. Doctors generally use a simple tape measure to check waist length, though researchers can use high-tech methods like CAT or MRI scans to examine the innards of an abdomen.
Q. What should you do about it?
A. Exercise helps greatly. Also, weight loss helps, and initial weight loss is often heavy on visceral fat.