November 2000 • Volume 6 Number 11
'Apples' and 'pears': defining the shape of the problem
BY CINDY McCANSE
Think about it: Lugging around those extra pounds can't possibly be good for you in the long run. Just consider the strain on the heart and joints, boosting the risk of cardiovascular complications and ost eoarthritis. And then there are the psychosocial implications: Obesity remains highly stigmatized in our society.
To make matters even more complex, it's now a well-established scientific fact that it's not just the extra weight that's problematic, but how that weight is distributed. Patients with an abdominal fat distribution pattern ("apples") face even greater health risks than those whose fat is deposited primarily in the thighs and buttocks ("pears").
The reason?
Abdominal fat cells are larger than those deposited in the lower body -- and they're more efficient at breaking down lipids into fatty acids, says Ahmed Kissebah, M.D., professor of medicine and chief of endocrinology, metabolism and clinical nutrition at the Medical College of Wisconsin, Milwaukee. Circulating free fatty acids hamper muscle cells' glucose uptake, which, in turn, elevates blood glucose levels and increases the risk for type 2 diabetes.
The picture is further complicated by the fact that fatty acids from abdominal fat can travel directly along the portal vein to the liver, where they suppress insulin breakdown. Resulting increases in circulating insulin can lead to decreased insulin sensitivity and insulin resistance.
The flood of circulating fatty acids may have other consequences as well, Kissebah and others believe. Namely, it appears to stimulate hepatic release of triglycerides, leading to atherosclerosis and increasing the risk of heart attack and stroke. Some even postulate that this barrage of fatty acids may in and of itself raise blood pressure, perhaps by increasing arterial sensitivity to hormones that mediate blood vessel contractility, such as epinephrine.
Upper-body obesity also affects respiratory function, according to obesity researcher Peter Kopelman, M.D., a professor at the Royal London School of Medicine who has studied the problem. Increased fat deposition in the chest wall and abdomen alters the mechanical properties of the chest and diaphragm, reducing lung volume and necessitating increased respiratory effort to compensate for decreased ventilatory capacity.
Typically, a waist-to-hip ratio value of greater than .80 in women and greater than 1.0 in men confers an increased risk for these complications. Obesity-related respiratory changes are exaggerated during sleep, often producing apnea and associated hypoxia, Kopelman says. Prolonged, severe hypoxic episodes can result in cardiac arrhythmias. Alternatively, chronic hypoxia and hypercapnia, pulmonary hypertension overlying an already stressed circulatory system and right-sided cardiac failure form the clinical picture of obesity-hypoventilation syndrome, previously known as pickwickian syndrome.
Although standardized height-for-weight charts, calculation of body mass index and measurements of skinfold thickness are all used to identify overweight and obese patients, waist-to-hip ratio is considered the most reliable method to differentiate apples from pears. Typically, a WHR value of greater than .80 in women and greater than 1.0 in men confers an increased risk for these complications.
While the science of obesity may be complex, the take-home message seems clear: Yes, size does matter, but in the end, it may be the shape that determines things to come.
FP Report is published by the AAFP News Department.
Copyright © 2000 by American Academy of Family Physicians.
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