“We used to think of the body as an isolated system that regulates itself,” said Professor Shir Atzil, a researcher at the Hebrew University of Jerusalem. “Our findings show that human physiology is inherently social. Being close to someone you love lowers the physical energy your body spends on regulating itself.”

“This gives us a direct metabolic benefit to being together and reveals a core evolutionary reason why humans form bonds in the first place: our bodies run better together.”

In one experiment, 108 adults ate a standardized carbohydrate meal — first alone, then with their romantic partner — while the researchers tracked their blood glucose for two hours.

Glucose levels rose less and returned to baseline faster when partners were present, producing about a 15% reduction in overall glucose exposure compared with the alone condition.

The scientists then repeated the design with two other physiological systems.

In a cold-exposure test with 116 participants, skin temperature dropped less and recovered more quickly when a partner was nearby.

In a mild-shock stress test with 115 adults, skin conductance — a marker of nervous-system arousal — likewise showed a smaller, shorter-lived response in the social condition.

A related pilot study of 56 mother-infant pairs found the same pattern: infants showed reduced stress responses to a loud noise when their mother was present in the room, compared with a separate-room condition.

Across all three adult experiments, a combined statistical analysis found a consistent effect, with roughly 8 to 12% lower cumulative physiological ‘cost’ in the social condition than when participants faced the same challenges alone.

Professor Atzil and colleagues argue the findings point to something they call Social Physiology, the idea that being near another person doesn’t just buffer stress or provide comfort, but can make routine bodily regulation itself more efficient, even in systems like glucose metabolism that aren’t usually thought of as socially responsive.

Notably, the glucose effect didn’t appear to be explained by reduced stress: markers of physiological arousal didn’t differ between the alone and social conditions during the eating experiment, and the effect held up even after statistically accounting for stress levels and physical touch between partners.

The authors suggest the benefit may instead involve the brain’s predictive regulation of the body — a process called allostasis, in which prior social experience helps the brain anticipate and manage physical demands before they fully unfold.