Seven is a powerful and highly symbolic number.

For example, there’s the Seven Deadly Sins. Most of us—regardless of religious affiliation—have at least heard about what theologians identify as sloth, envy, gluttony, lust, pride, anger and greed.

Or, if you prefer it in shorthand: Member of Congress.

Then there’s the Seven Cardinal Virtues: Chastity, temperance, diligence, charity, patience, kindness and humility.

In much the same way that half of all schoolchildren can’t find France on a map, I doubt if even a quarter of adults these days could actually define those first three virtues.

Nevertheless, like obscenity, even if we can’t define them, we know ’em when we see ’em.

Now consider another symbolic seven, one that has real relevance to the contemporary debates about diet and nutrition and their connection to animal agriculture: The Seven Essential Foods.

These are: Vegetables. Fruits. Nuts. Seeds. Meat. Eggs. Fish.

For millions of years, as best we can estimate, our human and pre-hominid ancestors lived solely on those foods. Nothing more. As human physiology evolved, that’s what people thrived on, and as a result, that’s what our bodies are genetically programmed to prefer.

Along with procuring the primitive versions of the plant foods with which we’re familiar, early humans spent the bulk of their productive time on Earth hunting, fishing and trapping animals that could provide sustenance.

What’s the point of mentioning all this? To underscore the dietary variables relevant to the nation’s current obesity crisis. To listen to activists critical of the very concept of animal agriculture, the “overconsumption” of red meat and poultry is a prime suspect in the development of the chronic diseases plaguing post-modern societies.

Yet the sea change that permanently altered humanity’s fundamental dietary patterns, ones that had existed for millennia, wasn’t the relatively recent growth in production and consumption of meat and poultry, it was the emergence of the agricultural technology to grow grains. As farming became more sophisticated, more productive and ever-expanding, people’s diets in many civilized regions of the world shifted from the cavemen’s menu of mammoth meat to the consumption of calories derived from grains: bread, pasta, beer, rice, potatoes, etc.

The statistics are staggering

In more recent times post-World War II that trend has increased exponentially. Even the stricter diet regimens suggested by a variety of nutritional experts recommend what are historically excessive amounts of calories from carbohydrates.

You can witness the results of such a significant dietary shift every time you stroll through the local mall, attend a ball game or ride a city bus. Heck, look around anywhere people congregate and you will have firsthand, eyewitness evidence of the statistics cited by a host of government agencies: Fully one-third of U.S. adults (34%) are classified as obese—that’s 72 million people—and more than two-thirds (68%) are considered overweight. Want to know the worst part? If the trend lines continue without interruption by 2020 exactly half of all the people in the United States will be obese. Not merely overweight—obese.

You can fudge those figures up or down; it doesn’t matter. The reality is that millions of Americans right now are fat, and millions suffer serious health issues because of being overweight.

It all comes down to human physiology. We’re simply not equipped to be consuming 50% (or more) of our daily calories from carbohydrates. Even if one were to dismiss the controversies over refined versus unrefined carbs, the reality is that, like Jack Nicholson’s character in “A Few Good Men,” we can’t handle the truth.

The truth being that we ought to start shifting our dietary preferences away from the foods and food products that historically as “unnatural,” and start consuming more of the seven essential foods that our bodies are best equipped to digest and which supply the nutrients we need.

All of this make the vegetarian diet, with its inordinate reliance on plant sources of carbohydrates and protein—to the exclusion of three of the seven essential foods—an even greater travesty than its supposed avoidance of cruelty.

We’re made to eat meat, and we have a million years of archaeological data to back it up.

That, plus the current evidence of how inappropriate our “modern” diets really are, which is accessible by going to any public place and simply scanning the crowd.

The bottom line is very simple: We’re not eating what we should be eating.

The opinions expressed in this commentary are solely those of Dan Murphy, a veteran food-industry journalist and commentator.