Vast majority of Americans overestimate diet quality

The only adults in the United States who accurately assessed the healthfulness of their diet were the ones who considered it “poor,” according to a presentation at the American Society of Nutrition Scientific Sessions and Annual Meeting.

“U.S. adults in general cannot accurately assess the quality of their diet,” Jessica Thompson, PhD, a research epidemiologist of the USDA Agricultural Research Service, said during the presentation.

Thompson and colleagues used data from the National Health and Nutrition Examination Survey — a program of studies that uniquely combines interviews with physical examinations — to analyze the nutritional status and overall health of people in the United States.

The researchers asked participants aged 20 years or older to rate the healthfulness of their diet from excellent to poor and measured diet quality by applying the 2015 Health Eating Index (HEI) to 24-hour dietary recalls.

The HEI — a diet quality tool that measures how a diet aligns with the Dietary Guidelines for Americans — calculates a score from 0 to 100 by analyzing 13 components, including nine adequacy components (fruits, vegetables, grains, dairy, protein, etc.) and four moderation components (refined grains, sodium, saturated fats and added sugars), Thompson said.

“Maximum scores are based on meeting or remaining under the highest recommended amount for each food group,” she explained. “Components are scored on a density basis out of 1,000 calories, except for fatty acids, which are a ratio of unsaturated to saturated fatty acids.”

The HEI scores followed the American grading system of A to F: “excellent” corresponded to scores from 90 to 100 (A); “very good” corresponded to scores from 80 to 100 (A or B); “good” corresponded to scores from 70 to 89 (B or C); “fair” matched scores from 60 to 79 (C or D); and “poor” indicated a score from 0 to 69 (D or F).

Of 9,757 participants, 8% rated their diet as “excellent,” 22% as “very good,” 41% as “good,” 24% as “fair,” and 6% as “poor.”

In measured diet quality, however, less than 1% — only 21 participants — fell into the “excellent” category and scored an A. Roughly 70% — 6,742 participants — earned an F. Only 3% scored a B, 9% scored a C and 19% scored a D.

“Out of the 9,757 adults included in our study, only 15% were able to accurately assess the quality of their diet,” Thompson said. “Note, however, in the poor group, that 97% accurately assess the quality of their diet.”

Between 1% and 3% of participants in the “good,” “fair,” and “poor” groups underrated their diets. The majority of participants, however, overrated the quality of their diet. Between 51% and 82% of participants who rated their diets from “fair” to “excellent” were instead found to have a poor diet quality.

“Although total and most diet quality components scores increased as adults’ perception of the healthfulness of their diet increased, the total diet quality score was below 60% — that is failing — for 70% of adults in our study,” Thompson said. “The tendency of U.S. adults to overrate the quality of their diet suggests that work is needed to educate adults about what constitutes healthful dietary intake.”