Overview

• An RCT published in Cell Metabolism assigned 43 healthy men to two three-week diet periods—ultra-processed versus minimally processed—separated by a three-month washout.
• Researchers observed drops in FSH and testosterone along with fewer motile sperm during the ultra-processed phase.
• Participants gained roughly 1.3–1.4 kg in three weeks on the ultra-processed diet, primarily as fat mass, whereas lower processing was associated with weight loss.
• Findings were seen even when energy intake was matched, suggesting effects beyond simple overconsumption.
• Authors note short duration, non-hospitalized monitoring and self-reported intake as limitations, and they propose pollutants with endocrine-disrupting activity as a candidate mechanism requiring further study.