In one segment of Morgan Spurlock's well-known documentary, "Super Size Me," he takes to the streets and asks a number of New York City residents, "What is a calorie?" No one comes close to the proper definition.

Talk about situational irony. In a country where two out of every three adults are considered overweight and probably at least that percentage have dieted on occasion, you would expect people to know the term responsible for weight gain or weight loss as well as they know, let's say, the jingle for McDonald's Big Mac something an entire family visiting Washington D.C., can recite for Spurlock in a humorous but pointed scene after repeatedly flubbing The Pledge of Allegiance.

So Spurlock interviews Marion Nestle, author of Nutrition in Clinical Practice and Food Politics, to provide the standard definition. She explains that a calorie is a unit of energy, technically the amount of energy needed to raise the temperature of one gram of water by one degree Celsius.

Ultimately, that unit of energy serves as a reference point. Quite often, you decide if foods are "good" or "bad" based on the amount of calories. You also determine portion size and your eating plan for the day based on the same.

While "Super Size Me" clearly showed that the typical American can't define a calorie, my guess is that most are also information deficient, so here are some of the most important information related to calories that have been published recently.

A study published in the January issue of the journal Medicine & Science in Sports & Exercise, reinforced something already well known: cutting calories leads to losing weight.

In a six-month study of 36 overweight men and women whose average age was 39, the group that cut calories by 25 percent lost an average of nearly 18 pounds but so did the group that cut calories by 12.5 and increased exercise to burn the other 12.5 percent. Most of the exercise group burned the additional calories by walking briskly four or five times a week, but the researchers allowed the subjects to change the intensity of the exercise and even the type if they so desired.

While my guess is that most people would rather exercise along with dieting to avoid the rather dramatic step of cutting cals by 25 percent, the researchers found another important reason why losing weight by a combination of diet and exercise is preferable. Those who exercised also recorded a reduction in blood pressure and an improvement in cholesterol as well as a greater sensitivity to insulin, a key in staving off diabetes.

Other research done with flies suggests that protein consumption more so than caloric reduction may be the key to healthy aging and even life extension.

Researchers from the Max Planck Institute for Biology of Ageing in Cologne, Germany used female fruit flies because even though humans have about four times as many genes as fruit flies, enough of the essential mechanisms are the same so that what applies to the one applies to the other. And what these researchers found was that calorie reduction was not the only way to get the life span of the female fruit flies to increase.

In the past, scientists have been able to increase the life span of fruit flies considerably by cutting a considerable amount of calories from their diet. While it's been hypothesized that the same would happen to humans, our life span and the discomfort created by eating 40 or 50 percent fewer calories for a lifetime makes research with humans impractical.

The Max Planck researchers, however, were able to elicit the same results without compromising the female fruit flies ability to reproduce by making sure the flies received the proper amounts of vitamins, fats, and amino acids (the building blocks of protein). But it was the manipulation of the amino acids that the researchers found that aided the female fruit flies the most.

What this suggests is that a steady stream of the right protein sources and the right type of other calories more so than the amount of total calories could allow humans to live healthier and longer lives.

Two other related articles showed just how the American public leaves its diet to chance and even possibly why there is an obesity epidemic. In the first, Margo Wootan estimates that Americans now consume one third of their calories in restaurants, and the second stresses just how frequently nutritional labels for reduced-calorie fare are inaccurate in restaurants and grocery stores.

Tufts University researchers analyzed 29 reduced-calorie restaurant menu items and found an average of 18 percent more calories than advertised. Analysis of 10 frozen meals purchased at grocery stores found those caloric totals off an average of eight percent.

Since an additional 100 calories a day produces more than a 10-pound weight gain in a year, this study suggests that consumers attempting weight loss need to be wary of foods that they do not make from scratch even the ones designed to aid weight loss.