Study details

For the study, researchers analyzed dietary information on almost 52,000 adults in the United States who participated in the National Health and Nutrition Examination Survey.

They found that the overall percentage of Americans who ate a poor diet dropped from around 49% in 1999 to 37% in 2020, while those who ate a somewhat better diet increased by 10.5%.

The researchers defined a poor diet as one with too many refined grains, processed meat, and sugary beverages, as well as too many ultra-processed foods that are full of added sugar, salt, and fat.

But while the percentage of people with a poor diet dropped, the percentage of Americans eating an ideal diet — which was defined as one with at least the daily recommended servings of fruits and vegetables, as well as more beans, whole grains, nuts, and seeds — rose less than 1%.

"We have stalled as a nation — and that does not bode well for our health," said Dariush Mozaffarian, director of the Food is Medicine Institute at Tufts University and senior author on the study. "If I was grading America on its diet, I'd give it a D—just up from an F."

"People often ask me, 'Well if the diet's slowly improving, why is obesity and diabetes still going up?'" Mozaffarian said. "It's still going up because only 1.58% of Americans have an ideal diet. We still have a long way to go."

Advances in nutrition were highest among women, younger adults, Hispanic adults, those with higher levels of education, and those with higher incomes who had access to private health insurance, the study found. Meanwhile, men, Black or older adults, as well as people with less income, lower education levels, non-private health insurance, and food insecurity issues saw fewer gains.

"We do need to avoid just blaming the victims of the dysfunctional US food system for the terrible diets documented in the survey," said Walter Willett, a professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health. "We fail to educate students about nutrition in our schools and feed them unhealthy diets."

"Our health care system is missing in action almost completely, we allow advertising to seduce children into junk foods and beverages that kill them prematurely, and we indirectly subsidize unhealthy foods in many ways that make healthier options relatively more expensive and less available to low-income Americans," Willett added.

How to improve your diet

Experts say there are several easy steps you can take to improve the quality of your diet.

For example, cooking at home as often as possible. "My top suggestion is to shop at the grocery store as much as you can, rather than getting your food at a coffee shop, sandwich shop, or quick-serve restaurant," Mozaffarian said.

Eating at full-service restaurants should also be limited, Mozaffarian added. Previous research from Mozaffarian and others found that around 80% of all food consumed by Americans at restaurants was of poor diet quality.

"Shockingly, even when we compared fast food versus sit-down restaurants, there wasn't a dramatic difference in quality," he said.

Instead, focus on minimally processed foods to cook at home and avoid the ready-to-heat convenience foods often seen in stores.

Mozaffarian also recommends avoiding sugary drinks, including energy, sports, and caffeinated drinks.

"Energy drinks, pre-sweetened iced teas, and specialty coffee drinks can have more sugar than soda," he said. "I see people walking out of the coffee shop with drinks with whipped cream on top. Don't drink your sugar."

However, Mozaffarian noted that once sugary beverages are removed from the diet, only "6% of calories in the country come from added sugar in foods. In contrast, about 35% of calories in the country come from refined grains and starches."

That's why Mozaffarian also recommends limiting how many refined grains you consume, which include foods like white flour, corn grits, white bread, and white rice.

According to Mozaffarian, refined grains are the biggest contributor to the poor quality of Americans' diets at 5.2 servings a day, which is "almost two servings a meal of refined grains such as refined bread, refined rice, crackers, chips, and other ultra-processed foods."

Whole grains still contain bran and germ, which are full of healthy fats, antioxidants, minerals, and vitamins E and B. They also take longer to digest, don't raise blood sugar as quickly, and contain more fiber.

According to the U.S. Department of Agriculture, some examples of whole grains include barley, bulgur, farro, millet, quinoa, black rice, brown rice, red rice, wild rice, oatmeal, and popcorn. 

Advisory Board resources on equity, SDOH, and obesity

For more resources regarding health equity, the social determinants of health (SDOH), and obesity, check out these Advisory Board resources:

• 4 ways health equity leaders can scale their impact
• Provider-led strategies to address food insecurity
• SDOH is a top priority for health system strategists. Here’s why.
• Diabetes and obesity care growth forecast: What you need to know
• 3 missteps in our approach to treating obesity (and 5 ways to fix it)
• 3 paths to the future of obesity care (and how to get there)

(LaMotte, CNN, 6/17; Thompson, U.S. News & World Report, 6/18)