Lean meat, poultry without the skin and fish are about the same calorie-wise. But what about health? Does it make a difference which you choose?

Nutrition experts -- and diet book writers -- are debating those questions, and two studies published this week in the American Journal of Clinical Nutrition hint at some answers that could help guide your food choices.

In one, Canadian researchers reported that an American Heart Association diet (about 50 percent of calories from carbohydrates, 30 percent from fat, most of them polyunsaturated) based on lean beef or poultry or fish worked equally well in cutting total cholesterol and low-density lipoprotein (LDL). A fish-based diet, however, outperformed lean beef and poultry in hiking protective high-density lipoprotein (HDL).

In another study, researchers from the U.S. Department of Agriculture and the National Institutes of Health examined a lean beef diet vs. a mostly fish diet (with some poultry) to see their effect on blood levels of healthy fatty acids, known as omega-3's.

Researchers first measured blood levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Don't worry about the names. All you need to know is that EPA is used to make a host of key substances in the body and likely helps account for the beneficial effects of omega-3 fatty acids on heart disease, arthritis and more. DHA is one of the most abundant omega-3's in the body, and is important for nervous system development and good vision. (In fact, the National Academy of Sciences found omega-3 fatty acids to be so important that it recently set recommended daily intake levels for them.)

In the study, 10 healthy adults ate breakfast and dinner under supervision of the researchers and were given packed lunches to eat at work. All calories were kept constant in both phases of the study. During the beef phase, lunch centered around roast beef sandwiches. Beef tenderloin was the main course for dinner. During the fish phase, lunch alternated between tuna and turkey sandwiches, with salmon as the main course for dinner.

EPA levels averaged about six micrograms per deciliter when the study began. During the beef phase they rose to nine micrograms -- not statistically different. But during the fish phase, they jumped to 19 micrograms, "a very significant change," says study co-author Norman Salem Jr., chief of the laboratory of membrane biochemistry and biophysics at the National Institute of Alcohol Abuse and Alcoholism.

DHA levels showed even more improvement on the fish diet. When the study began, they averaged about 27 micrograms and remained there during the beef phase. But they doubled to 55 micrograms on the fish diet, suggesting Salem says, "that in a couple of weeks you can double your level of DHA just by eating fish."

That could pay off, because studies suggest high levels of omega-3 fatty acids act as anti-inflammatory substances in preventing and treating heart disease and arthritis. They are also key for regulating heart rhythm, are essential for proper brain and nervous system function and may help prevent and treat depression.

Oilier fish -- salmon, trout, mackerel, sardines -- have the most omega-3's. "Here's where eating the higher fat content is good," says Salem, who has changed his family's eating habits based on the research. He buys only olive or canola oil, both rich in omega-3's, and avoids products with partially hydrogenated fats. "We try to eat fish at least three times a week," he says. "And we order fish when we go to restaurants."

Not that there's anything wrong with sometimes eating lean meat, beef or otherwise, Salem says. "It's just not good to eat it all the time."

MAKE THE MOVE

For Week Seven of the Make the Move Challenge, boost those two-minute walks to seven a day, or a total of 14 minutes. Consider taking a two-minute walk each time you end a task at work or at home, or get up each hour from 9 a.m. to 5 p.m. quick walk. Try to pick up the pace--or includes stairs--on some walks.

-- Sally Squires

Share Your Tips or ask questions about healthy nutrition and activity when Sally Squires hosts the Lean Plate Club online chat, from 1 to 2 p.m. today, on www.washingtonpost.com. New To The Club? The Lean Plate Club is devoted to healthy eating and boosting activity. To learn more, and subscribe to our free e-newsletter, visit www.washingtonpost.com/leanplateclub.