12 Surprising Reasons Why You Might Not be Losing Weight

You know about calories and portions and exercise. But if you don't know about these 12 surprising weight-loss traps, you may not see the scale budge.

1. You Assume "Healthy" Means "Low-Cal"

The label trumpets "low fat," "zero trans fats," or "no carbs." But these virtuous pronouncements don't tell you a thing about calories - which is what you need to pay attention to in order to lose weight and keep it off. "My rule of thumb is to look first at the calories per serving, then check the serving size," says Marion Nestle, Ph.D., professor of nutrition and food studies at New York University. You might be surprised by what the manufacturer considers a serving: For some cereals, like Grape-Nuts or certain brands of granola, it's only a half cup (compared to a cup and a quarter for Rice Krispies, say). "Once you match the product's serving size to what you'd actually eat, the calories might be considerably higher," says Nestle.

(Related: The Single Best Way to Lose Weight.)

2. You Discount the Little Things
Take the stairs instead of the elevator, park at the far end of the lot, walk down the hall to a coworker's desk instead of e-mailing.... You've undoubtedly heard these tips before - and you may have thought they couldn't make much difference. But just six 5-minute walks a day add up to about 100 calories, which translates into 10 pounds shed in a year. Keep on track by wearing a pedometer: A multicenter review of nine walking programs found that, on average, pedometer wearers walked an extra mile or so a day and lost about one pound every 10 weeks - without making a single change in their diets. (Think of what you could achieve if you stepped up your walking and cut calories.) (Related: The 30 Days to Thin Walking Workout)

3. You're Drinking Too Many Calories
No one knows why, but our bodies don't sense calories from liquids well, says Madelyn Fernstrom, Ph.D., director of the weight-management center at the University of Pittsburgh Medical Center. That signal failure can add up to a lot of pounds. Data from the Harvard Nurses' Health Study II on 51,603 women found that those who over four years increased their intake of sugar-sweetened soft drinks from one or fewer a week to one or more a day added 358 daily calories and put on an average of 10 pounds. Even drinks that sound innocuous - vitamin-enriched water or fruit-flavored iced tea - may be deceptively high-cal. Read labels and calculate servings. (Related: Find Out How Many Calories are in Your Cocktails)

4. You're Skimping - or OD'ing - on Sleep
Hopping out of bed a half hour earlier every day for a brisk morning walk is a great diet boost - unless you're not replacing that shut-eye. Multiple studies have shown that sleeping too little increases appetite, compromises insulin sensitivity (which can lead to weight gain), and affects other hormones that control hunger. Now a new report suggests that getting too much sleep might be linked to overweight. In a study of 276 adults, Canadian researchers found that people who slept nine or 10 hours a night put on about 3 1/2 more pounds over a six-year period than those who averaged seven to eight hours. If you're coming up short, turn off the TV and get to bed earlier. Spending too many hours in the sack? See your doctor - you could have an underlying health problem that's causing you to oversleep.

5. You're Caving on Cravings Too Often
Whether it's chocolate or chips, ice cream or whipped cream, the foods we crave have one thing in common: They are calorie-dense, a Tufts University study recently confirmed. But in that study, the researchers also noted that while virtually everyone has cravings, the dieters in the group who successfully lost weight or kept it off gave in to their must-haves less often. And when they did indulge, they kept portions reasonable. "Accept that cravings are normal, and then deal with them," advises Susan Roberts, Ph.D., professor of nutrition and psychiatry at Tufts. "Sometimes you can give in, and sometimes you need to brush your teeth and wait for the desire to pass." (Related: Conquer Your Food Cravings)

6. You Took a Break from Exercising
Maybe you got too busy with a PTA project or put in extra hours at the office, but a layoff can seriously interfere with weight-loss efforts - beyond the unspent calories. A recent study at the U.S. Department of Energy's Lawrence Berkeley National Laboratory found that joggers who temporarily cut back on distance or who stopped running altogether couldn't simply resume what they'd been doing if they wanted to drop the pounds they'd put on during their break. They needed to add extra miles in order to get back to their pre-"vacation" weight. (Related: Lose Weight Faster)

7. You've Banished All Carbs
It's not about food groups, it's about calories - consume fewer than you spend and you'll lose pounds. Does that mean you should eat a little less of everything? Probably, but tiny portions on your plate will signal "hunger" to your brain. "By the time we're adults, we've eaten thousands of meals and we have a good notion of what it will take to fill us up," says Barbara J. Rolls, Ph.D., professor of nutritional sciences at Pennsylvania State University. Eat too little at dinner, and you'll be charging the fridge before bed. Her solution: Put more veggies and fruits on your plate. True, they have carbs, but they also have fiber and water, and they're not high-cal. This way, you get the sensory experience of chewing and swallowing plenty of times, and your stomach gets filled without much risk of its also getting filled out. (Related: The Carb Lover's Diet)

8. You Listen to the TV, Not to Your Body
A recent study showed that Americans use external cues, like waiting till their TV show is over, to stop eating, unlike the don't-get-fat French, who rely on internal messages, such as feeling full. We're also susceptible to social influences. "Many of us keep eating until almost everyone at the table is finished," says Brian Wansink, Ph.D., a nutrition expert at Cornell University and the author of Mindless Eating. The damage can be serious if you're picking at the macaroni and cheese, so if you tend to finish before your family, "keep the salad bowl or veggies in front of you," suggests Wansink. Better yet, ask yourself if you're really still hungry. Unless the answer is truly yes, put down your fork.

9. You're Keeping Your Diet a Secret
Support is key to dropping pounds and keeping them off. That's why groups like Weight Watchers and online diet communities work so well. But be careful whom you turn to: Canadian researchers recently interviewed people trying to change their diets and found that some spouses actively hindered the dieters' efforts (by eating forbidden foods in front of them, for example). If that sounds like someone in your household, try an online buddy. (Related: The Best Diet Websites)

10. You're Working Out Too Hard
You may be setting yourself up to drop out. Research has shown that the best way to stick with an exercise program is to build confidence by starting slow and learning the proper mechanics - not by throwing yourself into it. And don't skip the cooldown. A study of 110 adults found that a happy ending makes the workout seem easier, "and in a related study we found exercisers reported they would be more likely to repeat the activity in the future," says study leader Britton Brewer, Ph.D., of the Center for Youth Development and Research at Springfield College in Massachusetts. Perhaps most important: You may be less likely to undo all the good by rewarding yourself afterward with a high-calorie treat.

11. You're Not Addressing Your Stress
Chronic tension alters hormones, like adrenaline, corticotropin, and cortisol, that can increase your appetite and make you store more fat. Normally, cortisol peaks in the morning, then decreases throughout the day. But a multicenter study found that women facing stresses at home often fail to show a drop in cortisol in the evening. That's when you're likely to turn to high-carb, high-calorie snacks for the soothing serotonin they trigger. Better, when stress is getting to you, listen to your favorite music or go outside for some "eco-therapy" (a.k.a. a walk), advises Kathleen Hall, Ph.D., founder of the Stress Institute in Atlanta. What may be most effective of all: concentrating on something you're grateful for. "It's physiologically impossible to be grateful and stressed at the same time because the two emotional states release different types of hormones," says Hall. (Related: 15 Easy Ways to Beat Stress)

12. You Don't Keep Track
You may think you're eating right, "but we're not as consistent as we think, and our memories are selective," says Fernstrom. The solution is to write it down. In a landmark Kaiser Permanente study of more than 2,000 dieters, keeping a food diary turned out to be the best predictor (even better than exercise habits) of whether people would lose weight. In other research, those who weighed themselves regularly after losing weight kept pounds off most successfully over the course of a year; while they regained slightly (two to four pounds), people who stepped on the scale less frequently put on an average of nine pounds. Buy a pretty journal or find an online weight-and-exercise tracker - whichever motivates you best.

More Diet & Fitness Advice from Good Housekeeping:
30 Easy Ways to Drop 5 Pounds
Test Your Calorie IQ
Find Your Perfect Slim-Down Solution with Our Diet Matchmaker
The Amazing Soup Diet: Lose 20 Pounds Fast
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Reprinted with permission of Hearst Communications, Inc.