Green nature effect on stress response and stress eating in the lab: Color versus environmental content.

Introduction: It is still unclear which green nature aspects can counteract psychosocial stress: the green color or rather the environmental content (=nature). Since stress is often stimulating excess/unhealthy food intake, we hypothesize that green nature also buffers stress-induced eating. This study analyzed the effects of green/nature pictures on restorativeness, stress reactivity/response and stress eating in the lab.

Methods: Before (5min) and after (8min) the Trier Social Stress Test, 81 participants (82% women, 19-30y) saw one of the four slideshows with nature or urban environments in green or black-white shades. Group differences were tested on Perceived Restorativeness Scale, five repeated measures of heart rate variability (HRV), salivary cortisol and mood, food wanting and snack buffet consumption.

Results: The four groups did not differ in background and baseline values. Reported restorative power was higher in the nature pictures than urban pictures with an even better attentional/happiness restoration capacity for green versus black-white nature, while green urban pictures might induce more stress feelings than black-white urban pictures. The stress time patterns confirmed successful stress induction. Most consistent during stress induction was a higher happiness recovery in the green nature group. Nature overall was somewhat beneficial compared to urban pictures by lower HRV and negative emotions reactivity, although this might be due to unfavorable effects of green urban pictures. In food intake or wanting, no differences existed.

Conclusion: Nature pictures were estimated higher in restorative power and green nature pictures had a positive effect on happiness recovery. Thus for prevention, the environmental content (=nature) as such seems important while just a green color seemed not enough. Future research should examine the effect of green nature in realistic indoor settings and consider influence on fruit/vegetable intake instead of solely snacks.