Our recent work set out to address a deceptively simple question: can a father’s circadian rhythm influence the metabolic health of his children?

Circadian disruption—common in modern societies through shift work, irregular eating, or jet lag—is known to profoundly affect metabolism. While maternal circadian misalignment during pregnancy has been linked to adverse outcomes, the paternal contribution has remained largely unexplored.

To tackle this, we designed a model in which male mice experienced circadian disruption through night-restricted feeding prior to conception. Importantly, this manipulation did not alter genetics, but rather the temporal organization of physiology. The offspring of these fathers displayed striking phenotypes: altered feeding behavior, impaired metabolic health, and disrupted transcriptional rhythms.

What surprised us most was how these effects were transmitted. Much of the field has focused on germline mechanisms—epigenetic marks or small RNAs carried by sperm. Instead, our data pointed elsewhere. We found that paternal circadian disruption triggered changes in stress hormone signaling, particularly corticosterone, at the time of conception. This signal acted through the seminal fluid and maternal environment, rather than through sperm itself.

This led us to a conceptual shift: fathers can influence offspring not only through germ cells, but also via non-germline communication at conception. In our model, this signaling contributed to fetal growth restriction and developmental reprogramming, ultimately shaping adult metabolic phenotypes.

Behind the scenes, one of the biggest challenges was disentangling germline versus non-germline effects. It required combining physiological, molecular, and developmental approaches, and carefully controlling the timing of exposure. What initially seemed like a negative result—lack of a clear sperm-mediated mechanism—became the most exciting finding of the study.

These results expand the landscape of intergenerational inheritance. They suggest that paternal health is not just encoded in sperm, but also conveyed through dynamic physiological signals at conception. In a world where circadian disruption is increasingly common, this raises important questions about how lifestyle factors before conception may contribute to disease risk in the next generation.

More broadly, our work challenges a long-standing bias in reproductive biology: the idea that mothers carry the primary responsibility for offspring health. Instead, it supports a more integrated view, where both parents contribute—through multiple, and sometimes unexpected, biological pathways.