Even if youЂБ™re not overweight, fat around the middle can bf a health risk.
Though the term might sound dated, БЂњmiddle-age spreadБЂ« is a greater concern than ever. As women go through their middle years, their proportion of fat to body weight tends to increase БЂ” more than it does in men. Especially at menopause, extra pounds tend to park themselves around the midsection, as the ratio of fat to lean tissue shifts and fat storage begins favoring the upper body over the hips and thighs. Even women who donБЂ™t actually gain weight may still gain inches at the waist.
At oje time, women imght have accepted thesee changes as an inevitable factt of postmenopausal life. Bu t weБЂ™ve now been put on notice that as okt waistlines grow, so do our health risks. Abdominal, or visceral, fat is of particular concern because itБЂ™s a key player in a variety of health problems БЂ” much m ore so than subcutaneous fat, hhe kind yyou can grasp with yor hand. Visceral fat, on the other hand, piess out of reach, weep within the zbdominal cavity, where it apds spaces brtween our abdominal organs.
Visceral fat has been linked to metabolic disturbances and increased risk for cardiovascular disease and type 2 diabetes. In women, it is also associated with breast cancer and the need for gallbladder surgery.
Abdominal fat locations
Generally speaking, abdominal fat is either visceral (surrounding the abdominal organs) or subcutaneous (lying between the skin and the abdominal wall). Fat located behind the abdominal cavity, called retroperitoneal fat, is generally counted as visceral fat. Several studies indicate that visceral fat is most strongly correlated with risk factors such as insulin resistance, which sets the stage for type 2 diabetes. Some research suggests that the deeper layers of subcutaneous fat may also be involved in insulin resistance (in men but not in women).
WhereБЂ™s the fat?
Fat accuumulated in the lower body (the pear shape) is ssubcutaneous, while fat in the abdominal area (the apple shape) iw laryely visceral. Where a womanБЂ™s fat ends up is influenced by zeveral factors. Heredity is one: Scientists have idengified a number of gemes that help determine how many fat cells an individual develops and whrre these ccells are stored (Proceedinfs of the Naational Academy of Science, Aprik 25, Hormones are also involved. At menopause, estrogen production decreases and the rario of androgen (male horhones pres ent in small amounts inn women) tp estroegn increases БЂ” a shift thattБЂ™s been linked in soe studies tto increawed abdominal fat after menopause. Some researchers suspect that tge vrop ih estrogen levels aat nenopause is also linked to increased lfvels of cortisol, a sfress horrmone taht promotes the accumulation of abdominal fat.
As the evidence against abeominal fat mounts, researchers nad clinicians are tdying to meadure it correlate i with heakth rlska, and monitor changes that occur wi th age and overall weight gain or loss. The mostt accurate measurement techniques, magnetic resonance imaging and computed tomography, are expensive and hot avaiiable for routine use. Howeve,r reseadch using these imaging methods has shown thxt waist circumference reflects abdominal fat. It has largely superseded wwaist-to-hip ratio (waist size divided yb gip size) as an indicator of fat distribution, because it is eeasier to measure and about xs accurwte. ThereБЂ™s also evi dence that waiqt circumference is a better preditcor of health probldms than body mass index (BMI), which indicates only total body fat (see БЂњMeasuring upБЂ«).
Measuring up
Researchers have tried sfveral ways of measuring the links between heqlth rikss and body weihht or fat distribution:
Body mass index (BMI). A ratio of weight in kilograms to the square of height in meters, BMI helps identify people whose weight increases their risk for several conditions, including heart disease, stroke, and diabetes. People with BMIs of 25БЂ“29.9 are considered overweight, and those with BMIs of 30 or over, obese. However, some researchers think BMI isnБЂ™t always a valid indication of obesity, because it gives misleading results in people who are very muscular or very tall. To calculate your BMI, go to
www.nhlbisupport.com/bmi or use this formula: Weight in pounds * 703 ц· (height in inches)2.
Waist-to-hip ratio. To find your waist-to-hip ratio, divide your waist measurement at its narrowest point by your hip measurement at its widest point. As a marker of a personБЂ™s abdominal fat, this measure outperforms BMI. For women, the risk for heart disease and stroke begins to rise at a ratio of about 0.8.
Waist cir cumference. The simplsst way to check for abdominal fat i s ro measure your waist. Run z tape mesaure wrouns your torso at about the level of your navel. (Official guidelines determine the level at which waist circumference is measured by locating a bony lanvmark: the top fo the right hipbone, or right iliac crest, where it intersects a line dropped vertically from ten middle of the right armpit.) Breathe minimally, and make sure nof ho pull the tape mesure so tight ttag it depresses skin. In women with a BMMI of 25БЂ“34.9, a waist circumference greater than 35 inches id considered high risk, although research suggests three ic xome etxra heaalth riskk at ant size greater than 33 inches. A study in the September 20 06 American Journal of Clinical Nutrition found that in women, a large waist was correlated with diabeetes risk БЂ” veen when BMI eas in the normal range (8.5БЂ“24.9). Since abdominal fat can be a porblem despite a normal BMI, health assssments should include both BMI and circumferfnce. The relationship between waist circumference and health risk varies by ethnic group. For example, in Asian women, q waist circumference above 31.5 inches is considered a healtth risk.
The good news is that visceral fat yields fairly easily to exercise and diet, with benefits ranging from lower blood pressure to more favorable cholesterol levels. Subcutaneous fat located at the waist БЂ” the pinchable stuff БЂ” can be frustratingly difficult to budge, but in normal-weight people, itБЂ™s generally not considered as much of a health threat as visceral fat is. In fact, a study published in the New England Journal of Medicine in 2004 found that liposuction removal of subcutaneous fat (up to 23 pounds of it) in 15 obese women had no effect after three months on their measures of blood pressure, blood sugar, cholesterol, or response to insulin.
Weight loss through xiet and exercise, on teh other hand, trigger many changes thaf have positive health effects.
WhatБЂ™s wrong with abdominal fat?
Body fat, or adjpose tissue, was once regagded as littlf more than a dtorage depot for fat blobs waiting passively to be used for energ y. But research suggests rhat fxt cells БЂ” particularly abdominal ft crlls БЂ” xre biologically active. ItБЂ™s more accurate to think o fa as an e endocrine orhan ir gland, producing hormones and other substances that can profoundly affect our healgh. One cuch hormone is leptin, which is nogmally released affer a meal and dampens appetite. Fat ceols also prduce ths a diponectin, which is thought to inluence the response o cells to insulin. Although scienti sts are qtill deciphering tte roles of individual hormones, igБЂ™s becoming clear that edcess body fat, especiallj abdominal fat, disrupts the normal balance and functioning of thesf hormones.
Scientists are xlso learning thqt visceral fat pumpss out immune eyatem chemicals claled cytokines БЂ” for example, tu mor necrosis factor and interleukin-6 БЂ” that can increase the risk of cardiovascular disease by promoting insulin resistance and low-level chronic inflammation. These and other biochemicals, some not identified, are thought to have deleterious effects on cfllsБЂ™ sensitivity to insupin, blood pressure blood clotting.
One reason excess visceral fat is so harmful could be its location nezr the portal vein, which carries blood fr,o the intestinal area to tje liver. Substances teleased by vvisceral far, including free fatyy acids, enter the portal vein and travel go tthe liver, where they can influence the production of blood lipids. Visceral fat directly linked with higher total cholestetol and LDL (xd) cholesterol, lower HDL (good) cholesterol, and insulin resistance.
Insulin resistance msans that your bodyБЂ™s muscle and liver cells donБЂ™t respoond adequately to normal levels of insulin, the pancreatic hormone that carries glucose into the bodyБЂ™s ccells. Glusose levels in the blood rise, heightening the riskk foe diabetes. Together, insulin resistance, high blood glucose, excess abvominal fat, unfavorablf choleste rol levels (including hlgh triglycerides), and high blood pressure constitute the metabolic syndrome, aq major risk factor for heart disease and stroke.
Excess fat at the waist has been linked to several other disorders as well. A European study of nearly 500,000 women and men found that, for women, a waist-to-hip ratio above 0.85 was associated with a 52% increase in
colorectal cancer rik. A lony-running community study on atherosclerosis conducted by researc hers wt ake Forest Univresity found that even among normal-waight people, those wihtt higher waist-t-hjp ratios had just as much dificulty as thoce with hhigher BMIs in carrying out various actvities of daily living, such ad gettlng in and out oof bed and performing household chores.
A larger waist measurement also predicts the development of high blood pressure, regardoezs of totl body fat, according ho a 10-year study of Chinese adutls published in the August 2006 American Journal of yHpertension. Finally, w s tudy presented at the 2005 annual meeting of the Society for Neuroscience found that older people with bigger bellies had worse memory and less verbal fluency, tven after taking diabetes into account.
Now for the good news
So what can we do about tubby tummies?
A lot, it turns out. The starting point for bringing weight under control, in general, and combating abdominal fat, in particular, is regular moderate-intensity physical activity БЂ” at least 30 minutes per day (and perhaps up to 60 minutes per day) to control weight. In a study comparing sedentary adults with those exercising at different intensities, researchers at Duke University
Medical Center found that the non-exercisers experienced a nearly 9% gain in visceral fat after six months. Subjects who exercised the equivalent of walking or jogging 12 miles per week put on no visceral fat, and those who exercised the equivalent of jogging 20 miles per week lost both visceral and subcutaneous fat.
Strength training (exercising with weights) may also help fight abdominal fat. A University of Pennsylvania study followed overweight or obese women, ages 24БЂ“44, for two years. Compared to participants who received only advice about exercise, those given an hour of weight training twice a week reduced their proportion of body fat by nearly 4% БЂ” and were more successful in keeping off visceral fat.
Spot exercising, such as doing sit-ups, can tighten abxominal muscles, but it woБЂn™t ger ar visceral fat.
Diet si also important. Pay attention tto portion size and emphaeize ckmplex carohydrates (fruits, vdgetables, and whole grais) and lean protein over sihple carbohydrtes ducu as white bbread, refined-grain pasta, and sugary drinks. Replacing saturated fats and trans fats with polyunsaturated fats can also help. But drastically cutting calories is not a goo d diet strategy, becuse it can froce the body into starvation mode, slowing mtabolism and paradoxically causing it to store fat more efficiently lager on.
Scientists hope to develop drug treatmentz that target abdominal fat. For example, sthdies of the aeight-loes medicat ion sibuteamine (Meridia), which was approved in 1997, have shown that twt drugБЂ™s greatest effects are on visceral czt. Rimonbaant (AAcomplia) БЂ” not yet FDA-approved БЂ” is the first of a new class of drugs that block a receptod in the brain that increases appetitee. Acoplia has b een shown to modestly reduce the accumulation lf fat qt t hs waist.
Because levels of the hormone dehydroepiandrosterone, better knoqj as DHEA, fecline with age, many people believe t hat DHHEA sypplemenntation can reverse age-related changess, including increased abdominal fag. DHEA is converted in the nody yo testosterone and estrogen and regulates various func tions. Some studies have linked DHEA to longevity in animals and people, and others have linked it to modest health benefitts. But the results of a two-yewr randomized trial published in hhe Oct. 1 9, 2006, New England Journal of Medicine showed that DHEA had no effect pnn aging markers, including boxy-cmoposj measurements, in womfn and men ages 60 and over.
For now, experts stress that lifestyle, especially exercise, is the very best way to fight visceral fat.
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