Where did she turn? To a local doctor who advertised 'before' and 'after' pictures of his clients. And now, several months later, our friend held out pictures of her newly-slim daughter.

What was the doctor's secret? To eliminate white flour and sugar because our friend's daughter supposedly "could not metabolize these food ingredients and, as a result, they made her fat." As diet myths go, this wasn't new to us. It's a good example of the magic bullet approach to weight loss, and also demonstrates how Americans are encouraged to adopt approaches that, in the long run, make them fatter.

Carbohydrates are carbohydrates. First, let's lay to rest the 'myth-conception' that white flour and sugar are metabolized by the body differently. It doesn't matter whether carbohydrates, the focus of a flour/sugar prohibition, come from whole grain or white flour, potatoes, pasta, fruit or table sugar. The body handles them all in the same way. True, some people with carbohydrate metabolism problems, such as diabetes, must be more careful about how much carbohydrate they eat. But a person with diabetes can still eat sugar. It's the total carbohydrate that counts, not so much where it comes from.

(To be clear, we're not denying the superior nutrition of whole grains, or that too much sugar isn't wise. We're just pointing out there is no scientific basis for claims that white flour and sugar are inherently 'bad' for you.)

So why did the diet work? Our guess is that our friend's daughter lost weight because she ate less. By eliminating white flour and sugar, she cut out a lot of the foods she regularly ate. Many foods contain these ingredients, so she was left with a fairly short list of 'allowed' foods, which reads a lot like many diets - no 'fun' foods that people, especially teenagers, sometimes eat a bit too much of. As a result, she cut her calorie intake dramatically.

So what? She still lost weight. Yes, she did. But unfortunately, the 40+-year history of dieting in this country doesn't convince us she will keep the weight off. Why not? Because she had to give up what were likely some of her favorite foods.

Picture her at the pizza parlor. Can she eat pizza with her friends, or does she have to limit herself to a salad? According to the doctor, it's the salad. But what's her inclination? The pizza, of course. So she eats it, and it's downhill from there. Because she hasn't eaten pizza for a while, she may overeat it just because it tastes good. Or maybe she plans to go back on her diet tomorrow, so she thinks she better enjoy all she can right now.

Thus she begins a pattern of overeating pizza. The diet theory tells her that she overeats it because she lacks willpower or some other unfounded premise. But whatever the reason, it becomes clear to her -- if she wants to remain slim, she will have to give up pizza forever.

We want what we "can't" have. The trouble is, forbidding foods -- the key to the white flour/white sugar theory -- doesn't work for the majority of people. Tell someone they can't eat salads, and they'll probably start thinking about salads more often. They may develop a penchant for salads, even though they didn't particularly like them before.

Maybe you aren't convinced a salad prohibition will cause this reaction. What if it's potato chips, ice cream, French fries or chocolate? It's easier to see how prohibition can set up an unusual desire for those types of foods. Then the desire can lead to a destructive cycle of overeating or bingeing on such foods, followed by an attempt at eliminating them, followed by feelings of deprivation, which leads back to an overeating or bingeing episode. We never learn how to eat these foods in moderation. Instead, they become triggers for overeating and feeling bad about ourselves.

The solution. To successfully achieve fitness goals, it's important to remove all judgment about whether a food is 'good,' 'bad,' 'fattening,' 'allowed,' 'high fat,' 'high sugar,' or 'illegal.' While awareness of nutrition is important, we want to make food choices based on total intake and how we feel, not on any one food's nutritional value. That way, we can enjoy all foods as part of a varied, balanced eating plan and still achieve our goals. We avoid feelings of deprivation, or not being satisfied with our meals and snacks, which can lead to eating for reasons that have nothing to do with physical hunger.

Achieving health and fitness goals also requires we meet our needs for physical activity, stress management, adequate rest, and having the right attitude about ourselves and our lives that can help keep us happy and well. But in our book, a life without chocolate...well, it's not a pretty picture!

A note about allergies and other food intolerances….
Some people have to avoid certain foods because the foods literally make them ill. To help participants come to grips with this, we encourage a focus on how a food makes us feel. Even though it may taste good initially, if a food makes us ill afterwards, our awareness of that - and the desire to not feel bad - can help make the food less desirable. Of course, the severity of the reaction contributes strongly to how undesirable the food will become. Ask a person who risks anaphylactic shock (a severe allergic reaction that can cause death) from eating strawberries, and she'll likely tell you she's happy to avoid them. With a less dramatic reaction, the desire may be slower to wane. But if we regularly eat other foods we enjoy, we can find that one particular food isn't important enough to risk feeling unwell.