There are a lot of marketing messages trying to get you to eat this or drink that, and while some are fact, many are fictions and fads. Here are the latest fads, foods and fictions on your supermarket shelves.

SPECIAL K DIET

Fad: On the Special K plan, you'll lose up to 6 pounds in two weeks. The plan: Eat Kellogg's Special K with 2/3 cup skim milk and fruit for two meals a day. Eat your third meal as usual. For snacks, choose fresh fruits and vegetables or a Special K Bar.

Fact: One cup of Special K has 110 calories. Add 60 calories for skim milk, 60 to 80 for the fruit and you're at about 230 calories per meal. Basically, you're lowering your overall calorie intake, so of course you're going to lose weight. However, can you get by on just a bowl of cereal with a piece of fruit for breakfast and lunch?

Fiction: There's nothing about Special K that will cause you to lose more weight than if you were having a low-calorie, healthy, water-based soup twice a day. You could call that the Soup Diet. Or how about the Carrot Stick Diet or the Oatmeal Diet? The question is: Can you stick with any of these diets? The answer is probably no.

Plus, Special K has added sugar and is not whole grain.

Bottom line: You probably can lose weight eating just cereal for two meals a day. However, if you substitute any lower-calorie food for what you ordinarily eat, you will lose weight over time.

YOGURT CEREAL

Fad: If your cereal is made with yogurt, it must be healthy.

Fact: Low-fat and nonfat yogurts can be extremely low in calories and have many reported health benefits, including improved digestion, prevention of intestinal infection and increased immune function.

Fiction: Unfortunately, you're not getting all those "yogurt" health benefits when you grab a box of Yogurt Burst Cheerios Vanilla or Life Vanilla Yogurt Crunch. The assumption that the yogurt coating is somehow channeling the health perks of regular yogurt is not accurate.

Bottom line: The coating appears to be nothing but a frosting. However, on the plus side, these cereals are made with whole grains, and the calories are not excessive — 3/4 cup of Life's cereal has 126 calories, while 3/4 cup of Cheerios has 120.

'WHOLE GRAIN' OFTEN MEANS NUTRIENT LOSS

Fad: Cereals, snacks, pasta — they're all becoming "whole grain" to convince you that eating them will make you healthier and trimmer.

Fact: When grains are refined, fiber and other nutrients, such as vitamin E, vitamin B6 and magnesium, are removed. There has been evidence that whole grains reduce the risk of cardiovascular disease, diabetes and certain cancers, whereas refined grains do not. Plus fiber increases feelings of satiety, which may help you eat less — and lose weight.

Fiction: Most whole-grain products do not have fewer calories than products made with white flour. That's not to say you can't find a low-cal whole-grain food — you can. But while switching from refined grains to whole grains is great, some of us simply eat too much of them.

Bottom line: They're better, but you can't give yourself carte blanche to eat more of anything that says "whole grain." The calories add up just as fast.

100-CALORIE SNACKS CONTROL PORTION SIZE

Fad: Balance Bars, Oreo Thin Crisps, Wheat Thins, popcorn packs. Food companies are packaging 100-calorie snacks on the theory that by limiting your snacks you will lose weight and be healthy.

Facts: Portion control is a huge issue. We eat what we see — therefore, packaging foods in smaller quantities helps. And seeing how little you get for 100 calories can also help you learn the true value of a calorie.

Fiction: "Know thyself." Will you really limit yourself to just one pack, or will you be going back for more?

Bottom line: If you can avoid going for more than one pack, and it helps to limit your consumption, this is a good way to stay on track.

LOW IN FAT AND CARBS BUT NOT IN CALORIES

Fad: The idea is that you will lose weight by consuming these foods, as opposed to traditional versions.

Fact: Sometimes low-fat or low-carb foods really are better choices, but it depends. The best examples of great low-fat foods are dairy products such as milk, cheese and yogurt, excellent sources of calcium. For instance, if you switch from 2 tablespoons of half-and-half in your coffee (39 calories) to skim milk (10 calories), you've just saved about 30 calories per cup. If you drink three cups per day, that's 90 calories or about an 8-pound weight loss in a year. Other low-fat/carb options that probably make a difference: mayonnaise, certain soups, sometimes even cakes, muffins and chips.

Fiction: Many of these foods don't taste very good, and/or have added sugar (low-fat foods) or fat (low-carb foods) and end up having roughly the same number of calories as their traditional counterparts. Also, sometimes when we eat lower-carb or lower-fat foods, we think it's OK to overindulge because it's "diet food."

Bottom line: Don't just go by what the label says. You also need to look at the calories, compare the taste and watch your behavior — do you end up eating more?

Charles Stuart Platkin is a nutrition and public-health advocate. Write to info@thedietdetective.com.