Q. A TV advertisement lauds a brand of peanut butter because it contains less sugar than others. Is this a reason for me to switch brands?

A. No. Peanut butters are quite similar to one another. According to the standard of identity, or legally defined recipe, to be called peanut butter, at least 90 percent of the weight of the finished product must be peanuts. That only leaves 10 percent for other ingredients, including stabilizers such as hydrogenated or partially hydrogenated vegetable oils, and "suitable seasonings."

Since a tablespoon of peanut butter weighs 16 grams, the total weight of all these other ingredients can be a maximum of 1.6 grams -- a little over 1/4 teaspoon. Clearly, brand-to-brand differences in sugar content would have to be small.

By the way, although suitable seasonings are allowed by the standard of identity, peanut butter cannot contain chemical preservatives, artificial sweeteners or flavorings, coloring agents or vitamins.

Q. Weight-loss programs often refer to "behavior modification." What does this involve?

A. According to Dr. Albert Stunkard and Howard C. Berthold, Ph.D., behavior therapy has five core characteristics. One is the assumption that all behavior, both normal and abnormal, is acquired and maintained along certain definable principles.

Second, people are better described by how they think, feel and act in specific situations (in other words, by their behaviors) than by emotions like insecurity and hostility. Third, therapy is very pointed and specific, and is evaluated by objective measures.

Fourth, treatment is customized for each individual. And fifth, there is continuous, critical assessment of the treatment.

In an article in the American Journal of Clinical Nutrition, Stunkard and Berthold grounded the behavioral principles of weight loss into seven categories. The first three include stimulus control (taking steps like shopping from a list, scheduling meals and snacks, and storing food out of sight), eating behaviors (doing nothing else while eating, putting down the food between bites) and rewards (planning specific rewards for specific behaviors). All these measures attempt to keep in check stimuli that might lead to overeating.

But that's not all there is to behavior modification. Other components include self-monitoring, detailed record-keeping, nutrition education, physical activity and so-called "cognitive restructuring." This involves, for example, helping individuals avoid setting unreasonable goals, and emphasizing progress, not shortcomings.

Q. Nutritionally speaking, is there any difference between honeydew and cantaloupe melon?

A. Yes, and the key lies in the color. Cantaloupe's orange hue signals that it's a fine source of beta carotene, which the body transforms into vitamin A. Just one cup of the melon more than covers the entire Recommended Dietary Allowance (RDA) for vitamin A. By contrast, the amount of beta carotene in honeydew in insignificant.

Other than that, the two types of melon are similar. A cup of either has about 60 calories and meets the RDA for vitamin C. They both provide potassium -- as much as you would get from 8 ounces of orange juice -- and small amounts of other vitamins and minerals. The weight of both honeydew and cantaloupe is 90 percent water.

Q. I ordered a salad in a restaurant, and it came with a green that had an interesting flavor. The waiter said it was called sorrel. Can you tell me about it?

A. Sorrel, also known as dock, is flavorful and versatile. It's used raw in salads (as you had it), as a filling in omelets, and as seasoning in soups and sauces accompanying eggs, veal and fish. It can be braised and pure'ed and served as a vegetable on its own, but because of its strong flavor it's more often mixed with other greens, such as chard or spinach.

In France and various countries, sorrel is well-known. In the United States, it is seen less often. You can find it in specialty stores and it does grow wild in some places, if you know where to look. It's quite easy to grow in your garden.

With respect to its nutritional profile, sorrel is a rich source of vitamin A. A quarter of a cup will give you half the day's allowance. It also contains some vitamin C, and it's very low in calories. All in all, sorrel is a nutritional bargain with a lot of flavor.