ReZoom

Our genes are at odds with our current style of eating and living. How did this happen? It all just got too easy ...There are now 45 million obese people in the United States, the majority of whom are over the age of 40. Since being overweight is a key reason that individuals develop diabetes, it is no mystery why America's medical community is alarmed by the now epidemic level of diabetes sweeping our nation's aging population.

The fact that two-thirds of the U.S. adult population is overweight or obese is a new phenomenon not only in our nation's history, but also in the evolutionary development of the human species. Can you imagine a Western movie portraying an overweight cowboy chasing down a steer or a 19th-century farmer tilling his field of vegetables with an overhanging belly? When American's men went to enlist in World War II, approximately 20 percent were turned away because they did not weigh enough. Even as recently as the 1950s, '60s and '70s, Americans were typically slim.

So what's happened? Our lifestyle and eating habits have changed – in fact, transformed – dramatically over the last 50 years. Fifty years is less than a blink of an eye within the context of human evolution.

How We Got This Way

These days, we are accustomed to getting our food by driving up to a drive-through window and placing our orders for "super-sized" portions. But our ancestors had to work for their food. Men went out and hunted and women foraged for nuts, berries, fruits, vegetables and roots. It was all a full-time job with lots of legwork. The men often trekked great distances in their search for game and often came home empty-handed. When a hunt was successful, the meat that they brought back "home" was leaner than the meat we eat today, because, unlike our modern-day, grain-fattened cattle, the animals our ancient ancestors ate were free-range and busy hunting for their next meal.

Our ancestors were subject to feast and famine. Because they did not know where or when they would encounter their next meal, our forefathers were conditioned to gorge when they did have available food. They would gorge and then efficiently store the excess so that they could make it through the long periods of time when there was nothing to fill their stomachs.

To survive as a species, our forefather's bodies evolved to be remarkably, metabolically efficient. This efficiency was due to the acquisition of "thrifty genes," which maximize energy from every calorie consumed. Thrifty genes helped keep our ancient relatives alive. But now, thrifty genes are what are causing obesity and diabetes – and not all of us have the same dose of these genes. Rates differ across the various ethnic and racial groups. This variability relates to the adequacy of the food supply and many other factors that different populations experienced throughout thousands and thousands of years of human development.

Those living where food was plentiful didn't need thrifty genes as much as those living where food was scarce. Those living in the European land mass, where the population was dense, learned to grow crops and domesticate animals. Today, their descendants have fewer thrifty genes than other ethnic and racial groups – and today their descendants have less diabetes and obesity.

It's Not Our Fault

There are evolutionary survival reasons why we like buffets and sweets.

Have you every wondered why you start salivating at just the thought of a bountiful buffet? Again, we are the victims of our ancestors who came before us. Their brains were wired to like a wide variety of foods so they could get all of the micronutrients and calories they needed. Eons ago, our ancestors had to migrate for food, and along the way they came across a wide variety. Their taste buds were ready for the varying commodities they found along the way. Now we wax eloquent on the shape, size, texture and taste of thousand of varieties of foods.

As well, our communal "sweet tooth" has its roots in biochemistry. There is little doubt that our fondness for sugar comes from an earlier attraction for sweet fruits that provided quick energy for a life that needed it in surges.

All of this is to say that the genes that we carry served our Paleolithic forbearers well. But they lived extremely active lives, had to undergo long periods of hunger and had diets that were low in fat. Those same genes are now challenging our capacity to maintain good health in times of abundance and sedentary lifestyles.

Give Our Body What It Needs

It will take hundreds if not thousands of years for our bodies to adapt to our contemporary way of life, long after all of us are gone. Our only hope for good health as a population is to recognize how our bodies are programmed and give them what they need to operate at their best. And that is just enough to stay in energy balance – so that the calories we take in equal the calories we burn.

Diabetes Series:

Last week: How diabetes became a silent epicdmic.

Next week: What you may not know about diabetes. It's worse than you think.

Francine R. Kaufman, M.D. is a past president of the American Diabetes Association and author of "Diabesity: What You Need to Know If Anyone You Care About Suffers from Weight Problems, Pre-Diabetes, or Diabetes."