Why Doctors Say Not All Fat Is Created Equal

The recent report that having a pot belly in your 40s roughly triples your risk of dementia in later life is just the tip of an ominous adipose iceberg.

Belly fat -- the visceral kind that accumulates around internal organs -- has also been linked to diabetes, high blood pressure, stroke, heart disease, gallbladder disease, sleep apnea and numerous cancers.

Having a big belly is even more closely correlated with health problems than obesity in general. Last week, researchers from Harvard Medical School reported that in a study of 44,636 women, those with waists larger than 35 inches were 79% more likely to die prematurely than those with waists less than 27 inches, even if their weight was normal.

For men, the danger point seems to be 40 inches or more. 'These guys with small behinds but big 'beer guts' are at greater risk for health problems than men with higher Body Mass Index, but relatively less fat in the abdominal region,' says Rudolph L. Leibel, co-director of the Naomi Berrie Diabetes Center at Columbia University Medical Center in New York.

What makes abdominal fat so sinister isn't completely understood. One body of research suggests that visceral fat may make metabolic mischief in its own right, promoting insulin resistance, a precursor to diabetes, and inflammation, which may lead to heart disease.

Another theory suggests that a big gut is essentially a marker -- an all-too-visible sign of psychological stress and other health problems, since the stress hormone cortisol seems to send fat into the abdomen. 'It's possible it's a semi-innocent bystander, like a canary in the coal mine,' says Dr. Leibel, who notes that if fat is building up inside the belly, it's probably also collecting in the liver, where it can lead to cirrhosis.

The connection with dementia is also not well-understood; it could be that belly fat is linked to high blood pressure and poor vascular function, which then leads to Alzheimer's disease; or it could be a more random association, like gray hair going hand in hand with heart disease.

Experts now think that subcutaneous fat -- the flabby variety under the skin in areas like the buttocks, legs and arms -- while unfashionable, is fairly benign. Researchers at the Washington University School of Medicine in St. Louis demonstrated that when they removed an average of 22 pounds of subcutaneous fat via liposuction from 15 overweight women, they found no change in the women's cholesterol levels, triglycerides, insulin sensitivity or other health risks. 'If they had lost that much fat by dieting, they would have substantially improved their metabolic profile, but they didn't,' says Samuel Klein, the study's principal investigator.

Of course, people generally can't choose where their fat is stored. That's determined mostly by heredity, hormones and aging. Men tend to deposit more fat in the gut than women, though after menopause, women start accumulating fat in the abdomen, too.

The good news for both sexes is that visceral fat is often the first to go when someone loses weight in general. Aerobic exercise, like walking or running, is particularly effective. Doing sit-ups, abdominal crunches and pilates can strengthen your abdominal muscles, and help hold your stomach in, but they won't target visceral fat specifically.

'I've seen guys at the gym with impressive six-pack abs, but their gut is sticking out,' says Michael D. Jensen, an endocrinologist at the Mayo Clinic in Rochester, Minn. 'The minute they stop working out four hours a day, they'll be in big trouble.'

Surgically removing visceral fat has been done on animals and some humans experimentally, but it is far more difficult and isn't likely to be a weight-loss option anytime soon.

Reducing stress may be helpful. But supplements that promise to flatten your belly by reducing cortisol could be harmful, some experts warn. 'Your adrenal gland is like a power tool,' Dr. Leibel says. 'You don't want to be messing around in the garage with it without supervision.'

Melinda Beck


>最近一项报告指出，如果你在40多岁时有一个大肚腩，那么在晚年患上痴呆症的几率大概
要增加两倍。不过，这也许只是肥胖所带来恶果的冰山一角。

内脏器官周围脂肪堆积而成的大肚腩还跟糖尿病、高血压、中风、心脏病、胆囊疾病、睡眠窒息和多种癌症有关。

大肚腩不只是过于肥胖那么简单，它与健康问题密切相关。2007年4月初，哈佛医学院(Harvard Medical School)的研究人员表示，经过对44,636名女子的研究，腰围超过35英寸的女子，即使体重属于正常范围，但未成年夭折的几率要比腰围小于27英寸的女子大79%。

对男子来说，腰围的危险临界点可能是40英寸以上。“与体量指数较高但腹部脂肪相对较少的男人相比，那些小臀但‘熊’腰的男人出现健康问题的风险更高，”纽约哥伦比亚大学医学院Naomi Berrie糖尿病治疗中心主任鲁道夫-雷贝尔(Rudolph L. Leibel)说。

我们还无法完全理解，腹部脂肪的危害为何如此之大。一个科研机构表示，脂肪堆积本身就会造成新陈代谢紊乱，导致身体出现糖尿病的先兆──胰岛素抗体并产生炎症，从而可能引发心脏疾病。

另一种理论认为，大肚腩从本质上讲是一种信号─表明此人心理压力很大，还有其它一些健康问题，因为这些情况下人体会产生应激激素皮质醇将脂肪送到腹部堆积起来。“大肚腩可能就像个旁观者，好比煤矿里的金丝雀，矿工从金丝雀的表现就能判断是否有瓦斯泄漏。” 雷贝尔医生说。他还表示，如果腹部有脂肪堆积，那肝脏可能也在堆积脂肪，从而可能导致肝硬化。

大肚腩与痴呆症的内在联系还不是很清楚，腹部脂肪堆积可能与高血压和血管功能退化有关，后者会引发老年痴呆症；或者，两者的关联性其实比较随机，就像灰白头发与心脏病同时出现一样。

专家现在认为，臀部、大腿和胳膊等处的皮下脂肪虽然不讨人喜欢，但相对来说是安全的。圣路易华盛顿大学医学院的研究人员做过一个试验，通过抽脂手术从15名超重女性身上取走平均约22磅皮下脂肪，发现这些女子体内的胆固醇、甘油三酸酯、胰岛素敏感度或其它健康指标均无变化。“如果这些脂肪是通过节食方式减下去的，那她们的新陈代谢情况应会有极大改观，但情况并非如此。”该项研究的负责人塞米尔-科兰(Samuel Klein)说道。

当然，通常来说人们无法选择自己体内脂肪的存储部位，这大多是由遗传、荷尔蒙及年龄决定的。与女性相比，男性的脂肪更容易出现在腹部；但在更年期后，女性也开始在腹部堆积脂肪。

不过也有一个好消息，一般来说，当男人和女人减肥时，最先减掉的往往是腹部脂肪。走路和跑步等有氧锻炼尤其见效，仰卧起坐、腹肌练习、普拉提塑身运动能锻炼你的腹部肌肉，减少赘肉，但它们并不专门针对腹部脂肪。

“我在健身房里见过有人举很重的东西，但他们的肚腩还是很大。”明尼苏达州罗切斯特市马约诊所的内分泌专家迈克尔-严森(Michael D. Jensen)说，“他们一旦每天锻炼时间少于四小时，身体就会出现大问题。”

通过手术减少腹部脂肪的做法有过动物和人体试验，但技术难度很高，近期不太可能成为减肥的方法。

一些专家警告说，减压可能有所帮助，但服用那些号称通过减少皮质醇分泌来改变大肚腩的保健药反而有害。“肾上腺素就像一台大功率机器，”雷贝尔医生说，“随便碰它可要不得。”

Melinda Beck