6 Warning Signs of a Bad Diet

Fad or not, some diets just aren't made to stick

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These days there's a new diet almost weekly, and it's easy to find their glittering promises alluring. "People are sick of their old habits and being overweight, and they're looking for something new," says registered dietitian Jessica Crandall, a spokesperson for the American Dietetic Association (ADA). But embark on a bad diet and you could pay a price beyond fleeting results. Some diets can cause a range of side effects, from bad breath and frequent urination, to fatigue and slowed metabolism.

That's why it's important to choose your diet wisely. For a diet that's going to yield long-term, healthy results, steer clear of these attributes:

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1. It's too restrictive. Diets are supposed to be restrictive, right? Well, yes and no. A healthy diet does entail some calorie cutting and self-discipline. But a diet that has too many rules spells trouble, Crandall says. "Extreme food restrictions are hallmark signs of a quick-fix plan," she says, adding that you shouldn't have to cut out your favorite foods completely—and doing so can intensify cravings. That's one reason diets that strictly limit food options, such as the Atkins and raw food diets, tend to have higher drop-out rates than, say, the Mediterranean diet, whose general guidelines leave room for variety.

2. It bans whole food groups. Removing food groups—or worse, entire macronutrients (carbohydrates, fats, and proteins)—can catch up with you quickly. These diets eliminate nutrients the body needs to function optimally. "The brain and muscles need carbohydrates," says registered dietitian Andrea Giancoli, a nationally known nutrition expert and nutrition policy consultant for the California Center for Public Health Advocacy, which helps cities develop and adopt healthful food and beverage polices. That's why low-carb, high-protein diets often cause weakness, irritability and fuzzy-headedness, she explains. And short-term fasts and detox diets, like the popular Master Cleanse diet (a hot water with lemon and maple syrup variation), can have lasting side effects, including slowed metabolism and lower bone density from calcium loss. "Diets that allow you to incorporate all foods in healthy portions are the ones people stick with long term," says Giancoli, who is one of 22 members of a panel assembled by U.S. News to rate diets.

3. It's the opposite of what you're doing. People often start a diet in desperation. "They feel so bad about what they've been eating that they want to make a drastic change," says Crandall. But you didn't form your habits overnight, so how can you expect an instant reversal? Better to start slow, reducing portion sizes and making simple substitutions like switching to a lower-calorie bread, she suggests. Small changes will help you avoid diet shock, which can quickly sour even the best plan.

4. It calls for extensive prep work. "Be cautious of plans that involve labor-intensive cooking or prep work," Crandall says. "With any diet, it shouldn't be too challenging." You still have to make a commitment to planning meals in advance, she says, but following 20-ingredient recipes, or cutting up four apples a day because it's in the diet is excessive—and likely won't help you stay on the wagon.

5. It comes in a package. Just as complex food preparation can be a diet's downfall, so too can over-simplified preparation, Giancoli says. Programs that hinge on prepackaged foods can leave you without an idea of how to prepare healthy meals on your own. "You don't know how to shop and cook for yourself. They don't leave you with any tools to adopt a healthful lifestyle," Giancoli says.

6. It touts a magic bullet. If a diet rules out obvious components of a healthy regimen, such as exercise or calorie monitoring, Giancoli's advice: run. "Some of these fad diets just talk about a certain food you need to eat. But when you consume too many calories of any food you're going to gain weight," she says. As for exercise, you can lose weight without it, but the body needs physical activity to be healthy, Giancoli says. Also, be wary of diets that promise drastic weight loss in a short time frame; as a general rule, healthy weight loss means losing 1 to 2 pounds per week.

"Most fad diets aren't designed to be a lifestyle change—they're designed for quick weight loss so you think they work," Giancoli says. By assessing the pitfalls of a diet program, as well as your own lifestyle and long-term nutrition needs, there's a good chance you'll find a diet worth sticking to.

Chelsea Bush writes for AskFitnessCoach, a site with straightforward advice on how to gain muscle and lose weight.