Only 28% of the participants had good agreement – defined as a difference of 6 points or less – between their perceived diet quality and its actual quality based on Healthy Eating Index–2015 (HEI) scores at the end of the 12-month intervention.
Even fewer – only 13% – had good agreement with their perceived and actual improvement in diet quality.
Jessica Cheng, PhD, Harvard School of Public Health, Boston, presented the findings in an oral session at the American Heart Association scientific sessions.
The study suggests that “patients can benefit from concrete advice on aspects of their diet that could most benefit by being changed,” Dr. Cheng said in an interview.
“But once they know what to change, they may need additional advice on how to make and sustain those changes. Providers may direct their patients to resources such as dietitians, medically tailored meals, MyPlate, healthy recipes, etc.,” she advised.
“The findings are not surprising given that dietary recalls are subject to recall bias and depend on the person’s baseline nutrition knowledge or literacy,” Deepika Laddu, PhD, who was not involved with this research, said in an interview.
Misperception of diet intake is common in individuals with overweight or obesity, and one 90-minute session with a dietitian is not enough, according to Dr. Laddu, assistant professor at the University of Illinois at Chicago.
“The Dietary Guidelines for Americans does a really nice job at presenting all of the options,” she said. However, “understanding what a healthy diet pattern is, or how to adopt it, is confusing, due to a lot of ‘noise’, that is, the mixed messaging and unproven health claims, which add to inadequacies in health or nutrition literacy.”
“It is important to recognize that changing dietary practices is behaviorally challenging and complex,” she emphasized.
People who are interested in making dietary changes need to have ongoing conversations with a qualified health care professional, which most often starts with their primary care clinician.
“Given the well-known time constraints during a typical clinical visit, beyond that initial conversation, it is absolutely critical that patients be referred to qualified healthcare professionals such as a registered dietitian, nurse practitioner, health coach/educator or diabetes educator, etc, for ongoing support.”
These providers can assess the patient’s initial diet, perceptions of a healthy diet, and diet goals, and address any gaps in health literacy, to enable the patient to develop long-lasting, realistic, and healthy eating behaviors.
Perceived vs. actual diet quality
Healthy eating is essential for heart and general health and longevity, but it is unclear if people who make lifestyle (diet and physical activity) changes to lose weight have an accurate perception of diet quality.
The researchers analyzed data from the SMARTER trial of 502 adults aged 35-58 living in the greater Pittsburgh area who were trying to lose weight.
Participants received a 90-minute weight loss counseling session addressing behavioral strategies and establishing dietary and physical activity goals. They all received instructions on how to monitor their diet, physical activity, and weight daily, using a smartphone app, a wristband tracker (Fitbit Charge 2), and a smart wireless scale. Half of the participants also received real-time personalized feedback on those behaviors, up to three times a day, via the study app.
The participants replied to two 24-hour dietary recall questionnaires at study entry and two questionnaires at 12 months.
Researchers analyzed data from the 116 participants who provided information about diet quality. At 1 year, they were asked to rate their diet quality, but also rate their diet quality 12 months earlier at baseline, on a scale of 0-100, where 100 is best.
The average weight loss at 12 months was similar in the groups with and without feedback from the app (roughly 3.2% of baseline weight), so the two study arms were combined. The participants had a mean age of 52 years; 80% were women and 87% were White. They had an average body mass index of 33 kg/m2.
Based on the information from the food recall questionnaires, the researchers calculated the patients’ HEI scores at the start and end of the study. The HEI score is a measure of how well a person’s diet adheres to the 2015-2020 Dietary Guidelines for Americans. It is based on an adequate consumption of nine types of foods – total fruits, whole fruits, total vegetables, greens and beans, total protein foods, seafood, and plant proteins (up to 5 points each), and whole grains, dairy, and fatty acids (up to 10 points each) – and reduced consumption of four dietary components – refined grains, sodium, added sugars, and saturated fats (up to 10 points each).
The healthiest diet has an HEI score of 100, and the Healthy People 2020 goal was an HEI score of 74, Dr. Cheng noted.
At 12 months, on average, the participants rated their diet quality at 70.5 points, whereas the researchers calculated that their average HEI score was only 56.
Participants thought they had improved their diet quality by about 20 points, Dr. Cheng reported. “However, the HEI would suggest they’ve improved it by 1.5 points, which is not a lot out of 100.”
“Future studies should examine the effects of helping people close the gap between their perceptions and objective diet quality measurements,” Dr. Cheng said in a press release from the AHA.
The study was funded by the National Heart, Lung, and Blood Institute, a division of the National Institutes of Health. Dr. Cheng and Dr. Laddu reported no relevant financial relationships.
A version of this article first appeared on.