(HealthiNation)

So you've got your plot to drop the extra pounds. It certainly seems sensible: You're going to eat right, eat less, and exercise. After weeks of declining dessert and diligently hitting the treadmill, you step on the scale and...only 2 pounds gone? You conclude that something or someone must be sabotaging you.

You might be right. While experts say weight loss can always be reduced to the simple "calories in, calories out" mantra—meaning if you eat fewer calories than you burn, you'll lose weight—a host of oft-hidden saboteurs may be meddling with the balance. Here's a smattering of them:

1. Treating healthy foods as low-calorie foods. "A lot of times they're not consistent," says Scott Kahan, co-director of the George Washington University Weight Management Program in Washington, D.C. So while whole grains, avocados, and nuts might be kind to your heart or cholesterol levels, dieters who binge on such foods can, before they know it, add hundreds of calories to the day's total. Enjoy calorie-rich healthy foods, dietitians urge, but ration them out: a quarter of an avocado on a salad or a small handful of almonds for a snack.

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2. Shunning shuteye. Some research has linked shorter sleep duration to a higher body mass index (a measure of body fat) and increased hunger and appetite. Additionally, if you're tired, you might be prone to grab a sugar-laden treat for a midday boost, skip the gym, and have takeout for dinner to avoid cooking. It's a vicious cycle. Aim for seven or eight hours a night.

3. Underestimating calories eaten. Quick—how many calories have you had today? No idea? Calorie ignorance is common and fueled by quite a few factors, dietitians say. First is a warped understanding of portion sizes. "People will tell me, 'Oh, I eat a half teaspoon of butter and I spread that on a piece of toast,' " says Ellen Liskov, a registered dietitian and nutrition specialist at Yale-New Haven Hospital. "I don't think you can do that mechanically." (People typically use a tablespoon or more.) You're going to have to recalibrate: Measure everything for a few days and work from recipes that calculate calories per serving or do it yourself. And be diligent about checking serving sizes. One sleeve of PopTarts, for example, is two servings. Also, be wary of seemingly innocent things like fruit, juice, trail mix, and dips. It's particularly easy to go overboard here.

Forgetfulness magnifies calorie ignorance. With all the to-do's jammed into your brain, you probably don't want to add a food diary. Too bad—your selective food memory is going to continue to sabotage you "until you start to pay attention every time you put something in your mouth," says Madelyn Fernstrom, founding director of the University of Pittsburgh Medical Center Weight Management Center and author of The Real You Diet. Also, while a couple healthy snacks strategically spread throughout the day is a good hunger-control tactic, Liskov warns of "random" snacking. You'll almost certainly lose track of all those calories.

4. Overestimating calories burned. "We tend to reward ourselves with too many calories of food for the amount of calories we burned exercising," says Kahan. Suppose you go for a 30-minute jog. The University of Maryland Medical Center's "calories burned calculator" estimates a 150-pound person would burn about 370 calories. Eat a few cookies later that day and you've just canceled it out.

5. Feeding your thirst. If you're not sure whether you're hungry or thirsty, assume it's the latter. Drink a water or tea and see how you feel. Some research even suggests drinking two 8-ounce glasses of water before breakfast, lunch, and dinner may help you manage hunger and eat less.

6. The food environment. Commercials on TV hawk junk food. Billboards for fast-food restaurants bombard you on the road. "We're in a society that really lends itself to eating a lot," says Kahan. Without addressing these saboteurs, he says, it's "almost overwhelmingly difficult" to lost weight. His solution: "Engineer your environment." At home, do a junk-food purge. At work, avoid the treats in the kitchen and lobby your coworkers to hide the Hershey's Kisses and go on a healthy-eating kick with you.

7. Saving up calories to eat junk. A couple hundred calories a day for an indulgence is OK, but don't get carried away. "You could eat a bag of chips 'til the cows come home, but that's not going to make you satisfied," says Marilyn Tanner-Blasiar, a dietitian at the Washington University School of Medicine in St. Louis. Without enough protein and fiber, you'll be ravenous an hour later and blow your calorie limit.

8. Medications you take. It's worth a check with your doctor if you don't know whether weight gain is a side effect of a medicine you're on. Psychiatric medications to treat bipolar disorder, schizophrenia, and depression, along with heart medications like beta blockers, commonly cause weight gain. While treating the primary condition is most important, says Kahan, you may be able to find a substitute sans the side effect.

9. Your family and friends. This can manifest in many ways. Maybe it's too heartbreaking to turn down grandma when she insists you have a third helping of her double-fried chicken. Or the rest of the family isn't on a diet, meaning some junk foods linger to tempt you. Perhaps your nights out with friends always revolve around food-and-drink binges. No wonder a 2007 report in the New England Journal of Medicine found that one's chance of becoming obese increase by 57 percent if a close friend becomes obese.

10. Yourself. Don't be overly restrictive. "If you set too many limits on yourself, you get bored and resentful. And that, mentally, will hinder your weight loss," says Tanner-Blasiar. Aim for slow and steady, shedding maybe a couple pounds a week, and don't obsess over the scale. You didn't gain the weight over the course of a couple weeks; likewise, it'll take more than that to lose it.

Above all, remember: "You can't be perfect. You can't be perfect in your relationships, in your job, in your life—certainly not in your weight-loss attempts," says Kahan. "There's nothing wrong with having a piece of cake on your birthday. There's nothing wrong with trying to aim for moderation."