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An exploration of explanation for the modern pandemic.

by Adrienne Dy, M.D.

JULY 2012

Centuries of combat with disease has seen many changes in the health battlefield. While many have perished to infectious plagues in the past, today’s pressing problems are mostly linked to more insidious causes. ‘Acute’ is giving way to ‘chronic,’ and while past epidemics wiped out majority of populations in one fell swoop, present-day pandemics are leaving a trail of people living with, not dying from, disease.

One of the most evident problems today is obesity—probably due to the undeniable visual reminders we see every day. It isn’t just your husband who’s piling on the layers around the middle—it’s men, women, the elderly, even the younger populations. Recent studies have pointed out how obesity even cuts across socioeconomic factors; in the U.S., the marginally poor and homeless have been paradoxically found to be obese rather than emaciated.

Many investigations have been made about the root cause of obesity. The first famous theory on the subject was pitched by geneticist James Neel.

The gift of thrift

Neel introduced the ‘thrifty gene hypothesis’ back in 1962 to initially explain diabetes. The large number of people afflicted with diabetes suggested a genetic component. Neel’s dilemma as a geneticist was, why would nature allow such negative traits to persist into modern times? Blatantly disadvantageous genes are usually removed by natural selection. So he theorized that these genes gave our ancestors some benefit during their time.

The hunter-gatherers had a harder time surviving. They lived in a feast-to-famine cycle—with periods of plenty until supplies lasted. Thus, Neel surmised that their bodies coped by developing a mechanism to store energy, probably in the form of fat stores, during bountiful times to give them a buffer for times of starvation.

That ancient genetic boon might well be the bane of today’s generations, who enjoy more stable food supplies. Our bodies still store fat in anticipation of food shortages that never come—and we don’t stop storing it.

Another take on the theory is the ‘thrifty phenotype hypothesis,’ which is a compromise between nature and nurture. It proposes that conditions inside the womb determine the probability of an individual becoming obese or diabetic later on. Poor fetal and infant growth translated to the development of these problems, because very early in life, the body had already begun bracing itself for the possibility of starvation. Children of poorly-nourished mothers are equipped to withstand low food supplies—but if they get lucky and experience more affluent lifestyles, then their thrifty phenotype or body type works against them.

The new malnutrition

While the thrifty gene theories have been debunked, rethought and revised many times, it is still a well-accepted belief that lifestyle diseases like diabetes and obesity are the result of both nature and nurture. That combination has reached a new permutation in developing countries, where it has been observed that obesity is fast becoming a problem in the poorer segment of their population. Common sense dictates that people used to starving wouldn’t have issues with weight gain. Yet in a recent study by Harvard Medical School, the medical records of more than 5,000 homeless Americans showed that only 1.6 percent were underweight; about 30 percent were of normal weight; and a whopping 60 percent were overweight—half of which fell into the obese category.

This illustrates the ‘hunger-obesity paradox’ coined by neurophysiologist Lawrence Scheier in 2005. An unstable access to food makes the poor binge whenever there is food, and starve when there is none—a simulation of the hunter-gatherer experience. The resulting weight problem may be the ancient mechanisms of energy storage kicking in.

However, this paradox is not generally true for the indigents of developing countries like ours. In the article Homeless and Overweight: Obesity Is the New Malnutrition by Brandon Keim, the proposed explanation is that the thrifty gene is not operating alone. The external environment—such as the access to cheap, filling, but not necessarily nutritious food—is needed for the paradox to manifest.

No matter what the cause, obesity is a real problem because of the maladies it brings, like diabetes and cardiovascular disease. Find out more in the July issue of HealthToday, out now in bookstores and newsstands.

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