With obesity rates climbing steadily—they're up 10% since 2000—and nearly 4 in 10 of us tipping the scale at unhealthy weights, America has earned the unwanted title of Fattest Nation on Earth. In addition, obesity-related health-care costs represent 20% of our health-care spending, or some $190 billion annually.

Those astonishing figures led Meifang Chen, PhD, MPH, CHES, professor of public health at California State University, Los Angeles, to look deeper. Specifically, she examined adoption and adherence to the Mediterranean diet across the country.

The Mediterranean diet has been shown to lower risk of obesity and is also linked to the prevention of cancer, diabetes, and heart disease—in other words, the big killers. This traditional diet emphasizes fruits, vegetables, nuts, fish, whole grains, and olive oil, while reducing saturated fat, refined sugar, and processed foods.

Coastal embrace

Chen and her fellow researchers studied nearly 21,000 non-Hispanic adults 45 years or older in 48 states and Washington, DC to determine how they followed the diet.

Participants completed a detailed food questionnaire at the start of the study, and the researchers calculated a Mediterranean diet adherence score for each participant based on the types of food they ate, ranging from zero to nine. The higher the score, the greater the adherence. The researchers also analyzed the geographical distribution of Mediterranean diet adoption across the US.

The average score was 4.36, and almost half (46.5% of participants) closely followed the Mediterranean diet. The researchers found that people in western and northeastern coastal areas, including California, Pennsylvania, New Jersey, New York City, Connecticut, and Massachusetts had the highest rates, whereas lower adherence clusters were largely seen in the South and East-North Central regions of the US, such as Arkansas, Louisiana, Alabama, Georgia, North Carolina, Michigan, and the northern area of Indiana.

There are many potential explanations for this, says Chen. Coastal areas are usually more urban, with diverse populations and a larger influx of immigrants. These factors may influence local residents' dietary behavior by exposing them to the cuisines of different cultures and thus expanding their palates beyond the Standard American Diet (SAD).

Less TV = healthier diet

Beyond the geographic findings, Chen's team found that people who lived in poor and rural areas, minority neighborhoods, and smaller towns were least likely to follow the diet, while it was more popular among older people and non-smokers, as well as those who were African American, college-educated, and had an annual household income of at least $75,000. Subjects who exercised at least four times a week and watched fewer than 4 hours of television a day were also more likely to eat a Mediterranean-style diet.

"Our study turned up some surprises," says Chen. "While previous studies found being white correlated with healthier diet adherence, our study found you are more likely to adopt and follow the diet if you are black. Future studies examining how race influences adherence are needed to determine if these results generalize."

Chen, who says she's a part-time follower of the Mediterranean diet herself, points out that the research shows it is the combination of foods that appear protective against disease, so it's important not to add just nuts or olive oil to your meals.

And, she adds, "The Mediterranean diet is not a diet, but a lifestyle. Living an active and social life is emphasized in order to gain the greatest benefits."