When it comes to body-weight maintenance or weight loss, the accepted belief used to be all calories are the same, or, as many nutritionists used to say, "A calorie is a calorie is a calorie."

Cursed with an incredible craving for fudge while on a 1500-calorie-per-day diet? According to the old line of thinking, you can eat nothing but 1500 calories of fudge one day and not derail your diet.

After all, a calorie is a calorie is a calorie.

While overeating a craved food for one day often cures a craving, recent research suggests that the all calories-are-equal theory is a bunch of bunk. A study published last year in the Journal of the Academy of Nutrition and Dietetics found a strong link especially for adults between consuming foods with a higher energy density and higher body weight.

In this study, the researchers reviewed 17 past studies on energy density and weight throughout the world. Fifteen of the 17 studies clearly showed that a diet lower in energy density but not necessarily lower in total total calories improved weight loss or the odds of maintaining a desirable weight.

How weight loss can occur without a reduction in total calories is explained in a concept nutrition guru John Parrillo calls nutrient partitioning. In short, the theory holds that because of the different ways in which the body handles the different macronutrients, protein and complex carbohydrates are unlikely to be stored as fat.

Even on a day where they are consumed in excess, and you exceed the number of calories you need to maintain your desired weight.

Fat and simple carbs, however, easily turn to fat, even when you don't exceed your target amount of calories for the day.

Furthermore, the concept of energy density itself explains why it's so easy to eat energy-dense foods in caloric excess.

A simple example establishes the concept. Every single gram of a raw potato contains .74 calories. So if you bake one that weighs 230 grams, about eight ounces, and eat it plain, you consume 170 calories.

If you eat eight ounces of potatoes in the form of French fries, however, the energy density increases dramatically because the potatoes are deep fried in energy-dense cooking oil. Get those fries from McDonald's, and you consume 754 calories, an increase of 584 calories.

In other words, you could eat three more eight-ounce baked potatoes two pounds of total food! and still consume 74 fewer calories than are found in the eight ounces of McDonald's French fries.

Subbing potato chips for French fries further increases the inequality. Eat eight ounces of plain Pringles, for example, and you ingest 1280 calories, over 1100 more than the plain baked potato of the same weight.

If you find the comparison of potato products a bit obvious, consider that I select my daily vegetables with energy density in mind. While I enjoy steamed broccoli, I love corn, yet I haven't had the latter in a very long time.

That's because there's more natural sugar in corn, which increases its energy density to such a degree that canned corn contains .54 calories per gram. Raw broccoli contains .27 calories per gram.

Since I can eat twice as much broccoli by weight for the same number of calories, I pass on corn time and time again.

Even if sugar and especially high-fructose corn syrup don't harm our health the way we fear they do, we should still avoid them because of what researchers have discovered about energy density.

Oatmeal, for instance, is seen as a great breakfast food. But that really isn't so if you eat a prepackaged portion with added sugars.

A packaged portion of Quaker Oats' raisin and spice contains 161 calories, 54 of which are sugars. Yet a packaged portion of Quaker Oats' low sodium because it has no added sugars, contain 103 calories, about 2 of which are natural sugars.

A change of one single serving from the former to the latter for one year creates a weight loss of six pounds. This example illustrates how reducing the energy density in your foods can be your saving grace if you want to lose weight or maintain a certain weight after following a weight-loss diet.

Other calorie-saving strategies include replacing protein sources like red meats high in fat with chicken and fish, exchanging sugar-sweetened beverages for ones with no calories, and substituting white bread and traditional pasta for versions that are whole grain.

Another sound strategy in the battle to control your body weight is to eat slower and chew longer. If you rush, you can down a ton of calories in 15 minutes, yet that's how long your body takes to recognize that it's full.

Eat more slowly and you'll find you eat fewer calories naturally.