Is "diet" really anything more than a marketing buzzword? That's the question bestselling nutritionist JJ Smith is asking, and the answer may be surprising. In her book Lose Weight Without Dieting or Working Out, Smith contends that most, if not all, of the products being labeled as diet may in fact be contributing to the obesity epidemic.

Naturally, everyone wants a convenient, straightforward and one-size-fits-all solution to the problem of putting healthy food on the table. Marketing gurus know this, and they've capitalized on the naivete of the average consumer.

"Most 'diet' foods are a gimmick, plain and simple," explains Smith. "The companies behind them are preying on the lack of consumer knowledge, all to make a fast buck. Unfortunately, these foods are more than worthless -- they may actually be contributing to obesity. To see why, you have to look at the biochemistry of hunger and fulfillment. Then, you'll realize how so many of these foods play tricks on the mind, starting a vicious cycle of unsatisfying meals and constant cravings."

Artificial sweeteners in those little yellow, pink and blue packages, for example, may have zero calories, but dieters pay for the instant gratification in the long run. These sweeteners actually increase appetite by sending false signals to the brain that sweet food is on the way.

When that food never arrives, the brain never gives the signal that the person is satisfied -- causing cravings for sweets. There's research that shows that aspartame in particular stimulates the release of insulin, which tells the body to store fat. "The bottom line," says Smith, "is that these calorie-free sweeteners actually contribute to weight gain."

Smith identifies some of the biggest culprits in the pyramid scheme of faux diet food:

1. Fat-free foods: These often contain higher-than-usual amounts of sugar, which cancels any benefits earned by the lack of fat.

2. Sugar-free foods: Be on the lookout for artificial sweeteners. They confuse the brain and lead to more cravings.

3. Diet soda: As with sugar-free foods, diet sodas contain worrisome amounts of artificial sweeteners, preservatives and food coloring.

4. Protein shakes and bars: Protein is fine, but the trouble starts when the body tries to break down the starches, sugars and other fillers in these "quickie" food substitutes. Hint: There's no "substitute" for real, nutritious food.

5. Fruit snacks: These are nearly always bursting with added sugar and artificial ingredients. They may taste like fruit, but they're nowhere close.

"I'm not the first to say this, but water and fresh, natural foods are what people are supposed to be eating, not processed junk," laments Smith. "Diet foods are just one more category of food best avoided, no matter what the advertisers say."