Dontcha love it? What I’m talking about here is the increasingly common “beer belly” on men of a certain age (mine) -- men who look nine months pregnant before the baby has “dropped;” You have a high, hard abdomen. Your jacket button doesn’t button any more. You can’t hug without first bumping into the huggee. I know. I was “there” once, before I lost 170 pounds.
I first came across the noun form “omentum” about six years ago in You on a Diet, a book by Dr. Michael Roizen, popularized by Oprah and later by a PBS series. The omentum is a sheet of fat that is covered by the peritoneum. The greater omentum is attached to the bottom edge of the stomach, and hangs down in front of the intestines. The other edge attaches to the transverse colon. The lesser omentum is attached to the top edge of the stomach, and extends to the undersurface of the liver. In humans, especially men who make bad choices about food (not necessarily beer), the omentum is a mass of fat around and especially in front of the stomach, liver, spleen, kidneys and intestines. It’s not healthy. There is a strong correlation between abdominal obesity, aka ‘central obesity,’ and cardiovascular disease.
This ‘visceral fat,’ also known as organ fat or intra-abdominal fat, is located inside the peritoneal cavity, packed in between internal organs and torso. It is differentiated from subcutaneous fat which is found underneath the skin, and intra-muscular fat which is found interspersed in skeletal muscle. Other distinctly different types of body fat include bone marrow fat and epicardial fat, deposited around the heart and found to be a metabolically active organ.
The immediate cause of obesity is a net energy imbalance. But the fundamental cause of obesity is not well understood, and many believe is a metabolic disorder of fat regulation. There is a growing consensus that, in humans, central obesity is related to the excessive consumption of fructose. It is also associated with elevated levels of the hormone insulin. In a large study (NHANES III), excessive waist circumference appears to be more of a risk factor for metabolic syndrome than BMI (Body Mass Index). The Index of Central Obesity is another measure more predictive of increased risk than BMI. See the Wikipedia entry or consult Medscape for more information on abdominal obesity, BMI and Central Obesity Index.
Central obesity is associated with a statistically higher risk of heart disease, hypertension, insulin resistance, and Type II diabetes. Belly fat is a symptom of metabolic syndrome (see http://danbrown-thenutritiondebate.blogspot.com, column #9).Central obesity is also associated with glucose intolerance and dyslipidemia (‘high cholesterol’), as well as a group of diseases that are either inherited or due to secondary causes (Cushing’s syndrome, PCOS, and treatment for AIDS).
There are numerous theories as to the exact cause and mechanism in Type II diabetes. Central obesity is known to predispose individuals for insulin resistance. Discoveries in recent decades have revealed that abdominal fat is especially active hormonally, secreting a group of hormones called adipokines that may possibly impair glucose tolerance. Central obesity seems to be the foremost type of fat deposit contributing to rising levels of serum resistin, one such hormone. Conversely, serum resistin levels have been found to decline with weight loss, especially decreased central obesity.
And if that ain’t enough, a study reported in the May 2010 Annals of Neurology examining over 700 adults found evidence to suggest higher volumes of visceral fat, regardless of overall weight, were associated with smaller brain volumes and increased risk of dementia, to wit, Alzheimer’s Disease.
Of course there are sex differences in fat accumulation. Female sex hormones cause fat to be stored in the buttocks, hips and thighs of women. Men are more likely to have fat stored in the belly. When women reach menopause and estrogen produced by the ovaries declines, fat migrates from the buttocks, hips and thighs to their waists and bellies.
So, what can be done about “omental adiposity”? Low fat and restricted calorie diets have not proven to be an effective long term intervention. Most people regain virtually all the weight that was lost and many regain still more. Spot exercises, such as sit-ups, crunches and other abdominal exercises are useful in building the abdominal muscles, but they have little effect, if any, on the adipose tissue located there. And, just for the record, there is little evidence that beer drinkers are more prone to abdominal adiposity than non-drinkers or drinkers of wine or spirits.
The best regimen for losing and keeping off excess omental weight – the pot belly – is a diet that provides satiety (a high fat diet), that digests slowly and restores skeletal muscle (moderate protein), and allows you to burn body fat for energy. See column #11 in my blog at http://danbrown-thenutritiondebate.blogspot.com. That means low carbohydrates. After the body burns the “sugars” in the carbs for energy, it turns to fat for energy, that is, your body fat. I know. I’ve regained some of the 170 pounds that I lost, but I have lost my “beer belly” forever.
© Dan Brown 12/7/11