Defiant claims of a renegade genius.
Watch out for a diet guru who professes to understand nutritional science but rejects it, contending that prevailing views on weight control are misguided. Posing as an unconventional genius who perceives truths mere mortals can't see is an easy way to get attention. Conventional wisdom is indeed wise—and hard earned, the product of painstaking research and long-term observation.

Dis-counting calories
Beware of any regimen suggesting that the key to weight loss lies not in controlling calorie intake but in tinkering with the body's level of a single hormone or chemical, such as insulin (Atkins, Sugar Busters, Carbohydrate Addicts) or eicosanoids, a class of hormone-like substances involved in many body processes, especially the production and prevention of inflammation. In reality, the regulation of weight involves the complicated interaction of many hormones and chemicals. It also rests on a simple truth: You gain weight when you take in more calories than you use up. If a fad diet works, it's because the dieter lowered her calorie intake.

Enticing testimonials
Ads for fad diets generally offer convincing quotes from highly-satisfied customers. These are as easy to obtain, as they are meaningless. The quotes may come from the brief period of peak satisfaction. How do these folks feel six months later, when the weight is likely to have come back? The ads don't say.

The promise of a quick fix
Fad diets promise—and may even deliver—rapid weight loss, offering a short-term solution to a permanent problem. The tendency to gain weight will not go away after a few weeks of eating only grapefruit or bacon. A diet so unbalanced that you can't stay on it for more than a few weeks or months without feeling awful is of no use for lifelong weight control. And the lack of balance can hurt your health. Extreme high-protein, low-carb diets can lead to vitamin deficiencies, a loss of bone density and other problems.

What You Should Do
What to do after you've protected yourself against squandering time, money and perhaps even your health on nutritional nonsense? Keep the constant company of your common sense and learn the skills and strategies you need to eat well despite the challenges of modern living—skills such as controlling hunger, balancing pleasure from food with pleasure in health and weight control, interpreting food labels so you can stock a pantry and fridge with healthful brands and products, making ingredient substitutions that add nutrition without subtracting taste, avoiding social pressure to overeat, and making physical activity an everyday part of life.

The Final Word
When you consider a new food program, first check to make sure it has none of the red flags listed previously. Remember that any weight control program that doesn't include physical activity isn't a good one. If you're a parent, consider whether it's a way of eating you would endorse for your kids. If it's not healthful enough for them—offering an abundance of vegetables, fruits and whole grains—it's not healthful enough for you! Ask yourself whether you'd feel comfortable and confident eating this way for the rest of your life. If not, it's an on-again, off-again diet, and these simply don't work.