To reach a healthier weight, you have to trim calories either by eating less, moving more or a combination of the two.

Trouble is that many people are pretty sloppy in calculating how many calories they eat. What's more, the heavier you are, the more likely you are to be inaccurate: Up to 46 percent of people who are overweight or obese underestimate what they eat by about 300 to 400 calories per day, studies show. That kind of miscalculation can thwart weight loss.

PDAs don't improve calorie count accuracy, a study found. Planning meals online may work better. (/ Ap) Low-Calorie Meal Planner Breakfast 1 cup cooked oatmeal -- 145 calories 1 cup skim milk --?80 WashingtonPost.com Poll When you're stressed do you: eat chocolate drink alcohol consume high-fat foods, such as French fries, fried chicken or taco chips all of the above View results Note: This is an unscientific survey of washingtonpost.com readers. Readers Diane Standiford (in photo) and Melanie Miller take the holiday challenge on video. Follow their progress through Jan. 1. Holiday Challenge Tips on Your Phone: This daily tip from Sally will keep you going throughout the challenge. The cost? $4.99. To get started, text LEAN to 99134. Click here to learn more. Take the Holiday Challenge: Find food and exercise goals, Sally's latest columns, worksheets, live discussion and more on the Lean Plate Club Holiday Challenge page. Save & Share Tag This Article  Saving options 1. Save to description:  Headline (required)  Byline 2. Save to notes (255 character max):  Blurb 3. Tag This Article

One solution is to let a computer do the counting. Personal digital assistants (PDAs) make it easy to record food eaten throughout the day. Scientists have theorized that these devices would make it easier to track food eaten and that "accuracy in counting calories would improve," notes Jean Harvey-Berino, chairman of Food and Nutrition Science at the University of Vermont.

But when Harvey-Berino and her colleagues tested that theory in a recent six-month study of 61 overweight adults who also received nutrition counseling, they found that using a PDA didn't improve the accuracy of counting calories. Nor did participants achieve "better weight loss," finds Harvey-Berino, who published the report in this month's Journal of the American Dietetics Association.

So what does work? Planning and portion control, experts say.

In a University of Pittsburgh study, researcher Rena Wing gave participants pre-measured food to eat, the same tactic used by such diet plans as NutriSystem, Jenny Craig and Slim-Fast. The approach "worked better than counting your own calories," Harvey-Berino notes.

That may be good for the short term, but few people are willing to permanently delegate their food choices to someone else -- or able to afford prepared meals for the rest of their lives. In a follow-up study, Wing and her colleagues provided menus and grocery lists and found that they were just as effective in controlling calories and fostering weight loss as providing the meals themselves. "The evidence for using menus and grocery lists is pretty strong," notes Harvey-Berino.

But planning meals can be challenging. A strategy that can make it easier is to use one of the free Web tools that are now available. In the evening, plan meals for the next day. Print the list and you've got a clear dietary game plan to follow. If the day doesn't go as expected, you can easily note the differences so that you don't go too far off course. Planning ahead helps you to stay on top of what you're eating and makes it more likely that you'll meet your calorie goals.

To test these tools, I plugged into each Web site a day's worth of meals and snacks that added up to about 1,500 calories. For an adult who needs 2,000 calories to maintain his or her weight, that intake would result in losing about a pound per week. This one-day meal plan mostly met the required nutrient intake for a healthy adult aged 50 or younger. It fell short only on calcium. (A single calcium supplement would fill the gap without adding calories.)

Here are the Web sites tested and how they stacked up for ease of planning meals:

Fit Day ( http://www.fitday.com/ ) This site generates lots of pie charts to examine what you're eating and burning. There's a nifty feature to customize your choices so you can tweak some of the standard calorie counts to better represent what you're eating. What I didn't like: Type in a simple food -- say, oatmeal -- and you have to wade through five pages of listings for oatmeal bread, oatmeal cookies and more just to find plain old oatmeal.

Nutridiary ( http://www.nutridiary.com/ ). Short on time? This site offers a guest feature that lets you use it without registering. It's a quick way to see how you like planning meals ahead of time. It also provides good, first-time user information. Another handy feature: You can turn off all ads on the site.

NutritionData ( http://www.nutritiondata.com/ ). If you like lots of additional technical information, this is the site for you. Nutrition Data not only records food, but it will guide you to better food choices with its Caloric Ratio Pyramid, Nutrition Balance Indicator and Nutritional Target Map. You can also plug in your own recipes and Nutrition Data will calculate the calories and nutrients and display a nutrient facts label with the information. To use this feature, however, you'll need to spend some time recording each ingredient in your online pantry.

Spark People ( http://www.sparkpeople.com/ ) This site asks for a lot of information before you get started, but that allows you to consider both your food and fitness goals. It sets daily calories, fat, carbohydrates, protein and water intake based on your goals. It also allows you to track up to 75 other nutrients, such as fiber, cholesterol and sodium, making it a good option for those who have special dietary or health needs. ?

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