U.S. Eating Habits Improve Some, But Unhealthy Diets Persist, New Study Finds

A poor diet continues to be a major risk factor for obesity, type 2 diabetes, cardiovascular disease, and some cancers. In a new study, researchers found that diet quality among U.S. adults improved modestly between 1999 and 2020.

However, the study also found that the number of U.S. adults with poor diets remains stubbornly high. And socio-economic disparities when it comes to nutrition persist and, in some cases, are worsening.

In the study from the Food is Medicine Institute at the Friedman School of Nutrition Science and Policy at Tufts University, published in the Annals of Internal Medicine, researchers focused on surveys by 51,703 adults between 1999 and 2020. Diet quality was measured using the American Heart Association diet score, a widely validated measure that includes components such as fruits, vegetables, beans and nuts, whole grains, sugary beverages, and processed meat.

Adedapo Iluyomade, M.D., preventive cardiologist at Baptist Health Miami Cardiac & Vascular Institute.

Researchers found that the proportion of adults with poor dietary quality decreased from 49 percent to 37 percent over these two decades, while those with intermediate diet quality increased from 51 percent to 61 percent. They also found that the proportion of adults with an ideal diet improved, but remained strikingly low, from 0.66 percent to 1.58 percent.

The Mediterranean Diet, promoted widely by nutrition and medical experts as ideal, earned the title of best overall diet for the seventh consecutive year, according to the 2024 ratings from U.S. News & World Report. 

Adedapo Iluyomade, M.D., preventive cardiologist at Baptist Health Miami Cardiac & Vascular Institute, prefers to think of the Mediterranean approach to food as a style of eating, rather than what Americans traditionally call a “diet.”

“As cardiologists, we're not fans of telling people to stick to a particular ‘diet’ because it gives off the aura of a fad,” said Dr. Iluyomade, who leads the Cardiometabolic Clinic at Baptist Health Miami Cardiac & Vascular Institute. “The goal, really, is to eat a well-balanced diet — one in which you focus on avoiding processed foods and increasing the number of fruits, veggies and whole grains. Whatever style of eating you use to come to that balance will be beneficial.”

The Mediterranean diet is primarily a plant-based eating plan that includes whole grains, olive oil and healthy fats, fruits, vegetables, beans and other legumes, nuts, herbs, and spices. Meat and dairy are eaten in smaller quantities, with the preferred animal protein being fish and seafood, followed by poultry. Red meat is eaten infrequently.

The U.S. government’s dietary guidelines, also known as My Plate, focus on plant-based options. About half of the government’s My Plate is fruits and vegetables, while the other half is grains and protein. Overall, 75 percent of the plate has always been plant-based.

Physicians and dieticians also recommend consuming less sodium, saturated fat and added sugars – all of which contribute to serious chronic conditions, including heart disease, high blood pressure, obesity and type 2 diabetes. 

Decades of research show that foods typical to the Mediterranean diet help improve blood vessel function, reduce the risk of metabolic syndrome and benefit the heart, Dr. Iluyomade says.

Metabolic syndrome is a group of conditions that together raise your risk of cardiovascular disease, diabetes, stroke, and other serious health problems. Metabolic syndrome is also called insulin resistance syndrome. Metabolic syndrome is common in the U.S. – with about 1 in 3 adults being diagnosed. The good news is that it is largely preventable

“The Mediterranean diet has been shown to reduce levels of C-reactive protein in the blood, as well as interleukin-6. These are markers that we use in medicine to determine the level of inflammation in a patient,” explains Dr. Iluyomade. “We know that chronic inflammation is really the driver of coronary artery disease and overall cardiovascular disease, so this anti-inflammatory effect appears to be one of the key mechanisms that benefit cardiovascular health.”

The new study found that gains in dietary quality were “highest among younger adults, women, Hispanic adults, and people with higher levels of education, income, food security, and access to private health insurance,” states a news release on the study from Tufts University. “They were lower among older adults, men, Black adults, and people with lower education, less income, food insecurity, or non-private health insurance.”