Whole Foods Market bills itself as a destination for organic and natural food, and the tactic seems to have worked, as a health-conscious crowd can often be seen at its prepared foods sections — and in particular, the salad bars. Armed with compostable containers, customers can be seen loading their trays with mixed greens and an array of cooked items such as tofu, stir-fry, and chicken.

While many prepared dishes at Whole Foods can be healthful, an analysis conducted by a laboratory on behalf of The New York Sun found that filling the containers can result in a single meal containing large percentages of the Food and Drug Administration’s recommended daily allotment of calories, fat, and sodium.

“This is another variation of supersizing,” a nutrition expert for the American Heart Association and a professor at the Albert Einstein College of Medicine of Yeshiva University, Judith Wylie-Rosett, said. “If you give someone a large container, they’re going to fill it up.”

Based on a 2,000-calorie-a-day diet, the FDA has recommended that the average adult consume no more than 65 grams of fat, 300 grams of carbohydrates, and 2,400 milligrams of sodium. The recommended amount of protein is 50 grams.

At Whole Foods, which charges $7.99 a pound for food at its salad bars, containers come in two sizes that can accommodate generous portions: The smaller holds 36 fluid ounces and the larger holds 54 fluid ounces. Competitors offer containers that come in a variety of sizes as well.

Health experts, physicians, and nutritionists said it is difficult for people to sample appropriate-size portions, which they defined as one-half cup, or four ounces, of one prepared food item.

“Visually, you’d want to fill the space,” a cardiac surgeon known for making frequent appearances on “The Oprah Winfrey Show,” Dr. Mehmet Oz, said.

“The average person who is going to a salad bar is overeating,” a registered dietician who is a spokeswoman for the American Dietetic Association, Keri Gans, said.

In the analysis, the smaller-size containers from Whole Foods were filled halfway with salad bar items that could be considered to be healthful, including Chicken Provencal, Vegan Chicken Delight, Spinach Orzo Feta Salad, Southern Sweet Potato Salad, and Vegan Peach BBQ Tofu Salad. The salad samples were then sent to Microbac Laboratories Inc., based in Warrendale, Pa.

The lab found that some of the food choices were high in fat, calories, and sodium. For example, the Southern Sweet Potato Salad, which weighed about 15 ounces, contained 70% of the recommended daily allotment of sodium, and the Vegan Peach BBQ Tofu Salad, also at 15 ounces, contained nearly 54% of a person’s daily allotment of fat.

“On the surface, some of these things look acceptable,” Dr. Oz, who is the director of the Cardiovascular Institute at NewYork-Presbyterian Hospital, said. In the case of the Vegan Peach BBQ Tofu Salad, he said, the fat content is too high for one sitting.

Dr. Oz, who said he rarely visits buffets, said consuming a fatty meal causes the arteries to constrict. “High blood pressure is one issue,” he said. “Over time, it actually damages the arteries.”

Still, smaller portions of some items would not be considered harmful. The Vegan Chicken Delight earned high marks from nutritionists, who said a four-ounce serving has 18% of the daily recommended amount of protein. This dish was also extremely low in calories, with about 3% of the calorie allotment for someone consuming 2,000 calories a day — in fact, some nutritionists recommended adding another salad to this choice

Someone who chooses a larger portion of a less healthful dish may be consuming too many calories. The Vegan Peach BBQ Tofu Salad, for example, contains 32.5% of a person’s recommended daily calorie intake in a 15-ounce serving. “The bottom line is two-thirds of the people in the United States are above what they should weigh. Foods like this contribute to that,” Ms. Wylie-Rosette said.

A spokesman for Whole Foods Market, Fred Shank, said the salad bar was designed to offer choices, and the supermarkets have proved to be very popular: Five locations have opened in New York City since 2001 and there are plans to open another three in the coming years. “It’s a self-serve bar. You take as much or as little as you want,” Mr. Shank said. “We give our shoppers the choice. We provide them with foods that are healthful foods, that adhere to our stringent quality standards.”

The salad bar containers were also designed to appeal to many customer types. “They can be used for one person or multiple people,” Mr. Shank said. “People should still control their serving sizes to maintain a healthy diet.”

He added that Whole Foods never claimed its products were low in fat, sodium, and sugar, and cited the store’s Web site, which contains photographs showing appropriate serving sizes for vegetables, fruits, and whole grains. The site does not include pictures of prepared foods.

At least one registered dietitian, Elisa Zeid, said some of the food descriptions might be misleading. “Vegan sounds very healthy, doesn’t it?” she said. “I think you have to read between the lines and go beyond the title of the dish.”

Ms. Zeid, author of “Feed Your Family Right!” said that 15 ounces of the Southern Sweet Potato Salad has “almost one day’s worth of sodium,” while a 15-ounce portion of the Vegan Peach BBQ Tofu Salad is “way too big.” She added that while tofu is healthful, the barbecue sauce — which contains sugar, syrup, and molasses — counteracts some of the nutritional value of the dish. “This meal is like lunch and dessert,” she said.

Nutritionists said people who combine smaller portions of the salads might also run into trouble. “You’re going to tend to fill up a huge plate or container,” Ms. Gans said.

If someone combined a half-cup each of the Spinach Orzo Feta Salad, the Chicken Provencal, and the Vegan Peach BBQ Tofu Salad, the meal would have 437 calories, 23 grams of fat, and 362 milligrams of sodium. “So it’s starting to add up,” she said.

In the case of the Southern Sweet Potato Salad, one four-ounce serving contains about 18% of the daily recommendation of sodium. “That sodium is scary, even for four ounces,” Ms. Gans said. “It’s just amazing. People will think, ‘Sweet potatoes are good for me.’ Yeah, but you’ve got to watch your portions.”

Still, some said Whole Foods does not purport to sell healthful foods, although the company promotes organic and natural products. “They talk about natural, or organic, or vegetarian, or vegan,” the executive director of the Center for Science in the Public Interest, Michael Jacobson, said. “Sometimes a lot of their products truly are healthy, and a lot of them truly are not.”