To achieve a healthier weight, you need to know the caloric score. The government's recent launch of a Web site to record food and physical activity highlights the growing number of free options that can do the numbers for you.

Why bother to keep food and activity records? Because studies such as the National Weight Control Registry of "successful losers" -- those who have lost at least 30 pounds and kept it off for at least a year -- finds that doing so is key to achieving and maintaining a healthier weight. Summertime, with its often-freer schedules and plenty of temptations, from ice cream to margaritas by the beach, is an excellent time to start.

With that in mind, here's a look at a few free online services that can help you avoid unwitting calorie creep. (From time to time, the Lean Plate Club will review others.)

My Pyramid Tracker (www.mypyramidtracker.gov). Launched in April by the Department of Agriculture (USDA), this Web site stores up to a year's worth of food and physical activity records. It also takes the guesswork out of meeting the latest U.S. Dietary Guidelines.

My Pyramid Tracker is a huge improvement over the USDA's previous site, but it still has some hiccups, as you'll see below.

To use the site, supply your age, sex, weight and height, then choose a user name and password. (For those worried about privacy, the USDA says that it does not track Web site users. There's also a browsing feature that allows you to take a look without first registering.)

Be prepared for tiny windows that are smaller than many commercial programs. Also record food in its most generic form as in milk, bread, cheese. beef or fish to save time. For example, plug in "skim milk" and up pop listings for chocolate syrup milk and a milk shake. Try "nonfat milk" and three listings appear for yogurt. Only by typing "milk" do you get the correct listing for skim milk, along with 1 percent, 2 percent and whole milk.

One part of the site, the healthy eating index, is still under construction. But a section that compares daily intake to the latest Dietary Guidelines is simple and fast to use.

The site's physical activity section will give your fingers and mouse a workout. To reduce clicks, take advantage of the frequently performed activities feature, which allows you to create a personalized list from 600 activities grouped into 21 categories.

Nutridiary (www.nutridiary.com). During a recent Web chat, some Lean Plate Club members searched for a free electronic way to record not just their daily eating habits but also brief notes on their progress. Nutridiary provides this and a whole lot more.

Like My Pyramid Tracker, Nutridiary allows guests to log in for several sessions before registering. Enter age, weight, height and sex and Nutridiary provides a daily basal metabolic rate plus a recommended calorie level that can help you lose -- or gain -- weight. There's a place to log body measurements from neck to calf size. In addition to the standard meal records, special logs track water consumption, fruit and vegetables, percent body fat and physical activity.

Build lists of meals and favorite foods to take advantage of the site's one-click shortcuts. Or add foods that aren't found in its database.

Use food and physical activity records to generate reports that chart up to six weeks of body weight trends, calories, body mass index (BMI), body fat percentage and calories in vs. calories out. There's also a handy electronic calendar with icons to remind you when weight, body fat and more were measured and a way to note the time of meals and physical activity.

NutritionData (www.nutritiondata.com). If you've ever wondered how many calories are in your homemade lasagna, this is the program for you. Plug in recipe ingredients to get a nutrition label that lists calories, protein, carbohydrates, fat grams, fiber and more, just like the labels found on commercially prepared foods. NutritionData also offers a color-coded pyramid to guide you toward healthier and more filling foods. Access it from the home page by plugging in a food near the large blue arrow on the top, right side.

Foods at the bottom of the pyramid are healthiest. So taco chips show up in the middle left, a measure of their good carbohydrates, protein and 44 percent fat. No need to guess better alternatives: NutritionData links to 50 healthier snacks, just as it does for other foods. It also features a fullness factor rating for foods, based on research from Pennsylvania State University, which finds that high-volume foods -- rich in water, puffed with air or filled with fiber -- help you feel satiated with fewer calories.

Meal records, however, take patience and practice. First step is to set up a personal pantry from a tab at the home page. From there, you can use a list to enter the foods consumed. Portion sizes are pre-set, such as 100 grams, eight fluid ounces or half a cup. If you haven't eaten those exact portions, you'll need to do some math. Then press a button called "Total +" to get the bottom line for the day. For die-hard number crunchers, one more click converts the tally to a spreadsheet that can be saved on your desktop and will give you further nutritional detail. Another site plus: a lengthy list of fast food, from Arby's to White Castle.

The site calculates physical activity, based on height, weight, age and sex. There's also a BMI calculator. NutritionData highlights the importance of "lifestyle" activities. Logging 9,400 steps on a pedometer -- about four miles -- counts as "somewhat active" category. Boost it above 9,400 steps daily to qualify as active.

*

Share your tips or ask questions about nutrition and activity when Sally Squires hosts the Lean Plate Club online chat, from 1 p.m. to 2 p.m. EST today, on www.washingtonpost.com. Can't join live? E-mail leanplateclub@washpost.com anytime. To learn more, and subscribe to our free e-newsletter, visit www.leanplateclub.com.