Have you ever wondered why it is that some people accumulate fat predominantly in the abdomen, while in others the fat is spread all around? Are people who are generally thin but have big bellies at high risk for chronic diseases, such as diabetes and heart disease although they have normal weight?
I’m sure we can all recognize abdominal fat when we see it, and a measuring tape quantifies what the naked eye easily identifies. Other names include “central fat”, “beer belly” and “visceral fat.” The latter term actually helps explain why abdominal fat behaves differently: The viscera are our internal organs, and visceral fat is the fat deposited between the abdominal organs in the torso, as opposed to subcutaneous fat, which is fat under our skins—the type you can pinch between your fingers. Abdominal or visceral fat is especially active metabolically and plays a part in insulin resistance and diabetes, lipid abnormalities, hypertension and cardiovascular risk.
Several studies have shown that fat distribution patters do matter.
A huge new study in the New England Journal of Medicine confirms this notion. It shows that abdominal obesity is more closely associated with the risk of chronic diseases than is general obesity, and that waist circumference or the waist-to-hip ratio, may be better predictors of the risk of disease than the body-mass index (BMI).
This study comes from the European Prospective Investigation into Cancer and Nutrition (EPIC), one of the largest long-term prospective studies in the world, which studies the relationships between diet, nutritional status, lifestyle and environmental factors and the incidence of cancer and other chronic diseases.
In this study, the researchers looked at 359,387 participants from 9 European countries. During the follow-up period, which averaged almost 10 years, 14,723 (or about 4%) of the participants died. The data suggest that both general fatness and abdominal fatness are associated with increased risk of death.
After taking general fatness into account, waist circumference and waist-to-hip ratio were strongly associated with the risk of death independently of overweight. People with the most belly fat had about double the risk of dying prematurely as people with normal amount of belly fat, and death risk increased with waist circumference whether the participants were overweight or not.
This study, essentially confirms what we already know: Excess body fat affects mortality, and the effect depends not only on the amount of extra fat (as reflected by BMI) but also on its distribution, with belly fat predicting higher risk.
This study provides important further evidence that in normal weight individuals abdominal obesity is a significant risk factor.
The authors write:
And they advise:
“Our finding of a positive association between waist circumference and the risk of death among participants of normal weight may also explain why studies have been unable to show a linear relationship between BMI and the risk of death across the entire range of BMI values.”
“The results support the use of waist circumference or waist-to-hip ratio in addition to BMI in the assessment of the risk of death, particularly among persons with a low BMI.”
As to why some people accumulate fat in the center, while others spread it around, there are no clear answers. Some ethnic groups—such as Asian Indians and Hispanics—have a higher tendency to accumulate abdominal fat, as do children born small who rapidly gain weight between the ages of 4 and 7 years. Aging, imbalanced hormones, being male, over-intake of sugars and lack of exercise have all been suggested to be factors for belly fat accumulation, too.
As to the “beer belly” theory: There’s a common belief that beer drinkers have bigger bellies than either nondrinkers or drinkers of wine. The few studies on the association between consumption of beer and abdominal obesity produced inconsistent results. Beer has plenty of calories (an average of 150 calories for a 12 oz. bottle), so drinking lots of beer regularly adds a lot of calories one needs to burn, otherwise fat will accumulate. However, I don’t think there’s good evidence to show that this fat will find its way specifically to the abdomen.
What’s clear is that, unlike banks, which give us a choice of where to deposit our money, we don’t get to choose where to put our fat. And unfortunately, no amount of sit-ups will make a fat belly go away. The overlying muscles will get stronger, but the fat inside won’t dissolve preferentially in the exercised areas.
So what to do about abdominal fat? Lose weight. That, of course, is easier said than done, but the good news is that visceral or fat is lost preferentially with even modest weight loss—belly fat is the first to go when you diet!