Despite the rise of plant-based eating, it seems Americans still prefer cheeseburgers to veggie burgers. And the proof was gathered on the beauty shop floor. Researchers from the University of Utah scrutinized chemical traces in discarded hair from barbers and hair salons in 65 cities across the United States and found that corn-fed animal-derived proteins like beef and dairy account for 57% of the content of American diets, on average. Variations in carbon isotopes found in hair reflect those found in different food products, making this method an intriguing way to understand dietary choices among different population groups.

As reported in the journal PNAS, the amount of protein consumed was also found to be higher in ZIP codes with a lower socioeconomic status, where corn-fed animal-derived protein accounted for as much as 75% of diets. What’s more, the authors discovered that the isotope ratios reflecting a higher proportion of animal-based protein in the diets of certain ZIP codes were correlated with elevated obesity rates.

See also: Americans Are Still Eating a Lousy Diet