Overview

• University of Copenhagen researchers ran a randomized, crossover study in which participants ate a high–ultra-processed menu and a mostly unprocessed menu for three weeks each with matched calories and nutrients.
• On the ultra-processed arm, men accrued about 2.2 pounds of fat, showed higher blood levels of the phthalate cx-MINP, and had declines in testosterone and sperm production.
• The work, published in Cell Metabolism, reports rapid biological changes that the authors say warrant rethinking dietary guidance and closer scrutiny of processing-related exposures.
• Investigators acknowledged key limits, including a small, male-only sample and short duration, and experts note uncertainty over whether harms stem from processing, contaminants, or formulation.
• Ultra-processed products supply roughly 60% of U.S. calories, though some nutritionists stress these foods are not inherently harmful and advise focusing on overall diet quality and balance.