(RNS)--Even given its oversized plates piled high with mashed potatoes, turkey, homemade stuffing, candied yams, a plethora of vegetables and pumpkin pie  – followed by after-dinner lethargy — Thanksgiving may be the one day that Americans are not guilty of gluttony.

The November holiday is, after all, about expressing gratitude, building family memories and celebrating the Earth’s bounty. The annual occasion promotes taste, togetherness and joy.

It’s the other 364 days of the year — like Black Friday — we should be worried about, said Mary Louise Bringle, professor of philosophy and religion at Brevard College in North Carolina.

“Sitting around the table at a feast is not a gluttonous act,” Bringle said. “Sitting in front of the television gobbling potato chips is.”

Gluttony as sin is a centuries-old concept, said the professor, author of “The God of Thinness: Gluttony and Other Weighty Matters,” but applies even more today.

Contemporary Americans are obese and anorexic, diet obsessed and food snobs, vegan and omnivorous, nibblers and pigs, counting calories and piling on toppings.

Some ancient Christians knew better, Bringle said. Our relationship to food should be one of reverence and thankfulness; our bodies should be temples.

The idea of gluttony as evil originated with Egyptian monks in the fourth century, she said. They renounced earthly pleasure to get closer to God, and their greatest temptations were food and sex. Thus, gluttony and lust topped the monks’ list of no-nos.

But when the categories moved from the monastic into the masses of humanity, these two became the least important, Bringle said. “It was an issue of balance.”

Food is not the enemy, she said. Excess is.

Pope Gregory in the seventh century expanded the notion of gluttony from mere overeating to include also eating too early, too eagerly, too expensively and with too much or too little attention.

Thus, he argued, it is wrong to think about food the minute you awake, to eat rapidly without saying grace or to fail to recognize God’s hand in providing the sustenance. It is sinful, then, to stuff yourself rather than savoring each bite, to spend so much on food that you go broke, or to be too picky about what you eat.

“Eating too much is a small part of gluttony,” Bringle said. “Fixating on three grapes and two curds of cottage cheese is a form of gluttony. Buying Lean Cuisine and obsessing about fat grams is gluttony.”

Indeed, she said, anything that keeps us from accepting the gift of food with humility and moderation is a sin. Both self-indulgence and self-denial undermine our relationship to God, the Earth and others.

“Christian moralists argued that it is as big a sin to fast on feast days,” she said, “as to feast on fast days.”

Gluttony, Bringle said, is a symptom of other, greater failings — such as pride, vanity and selfishness.

Clearly, America knows a lot about those.

The sin in all this greedy consumption, according to St. Thomas Aquinas, is not in the food, the cars or the clothes, but in the ravenous yearning for more, more and more.

“The vice of gluttony does not regard the substance of food, but in the desire thereof not being regulated by reason,” Thomas wrote. ” It is a case of gluttony only when a man knowingly exceeds the measure in eating, from a desire for the pleasures of the palate.”

That’s often the case these days.

Obesity has ballooned to an epidemic in the U.S., food portions have expanded, plates have grown ever larger and daily caloric intake has skyrocketed.