Scientists at The Institute of Cancer Research, London, found that body mass index, waist-hip ratio, waist-height ratio and waist circumference in women increased with increasing exposure to light at night.
These associations were still seen after adjustments were made for confounding factors that could be associated with light exposure levels and weight in the study participants, such as physical activity, having young children and sleep duration.
The findings come from cross-sectional analyses of data from the Breakthrough Generations Study, the largest study of its kind, following more than 113,000 women from across the UK for 40 years in a bid to find the root causes of breast cancer.
"Metabolism is affected by cyclical rhythms within the body that relate to sleeping, waking and light exposure," said Anthony Swerdlow, Professor of Epidemiology at The Institute of Cancer Research, and co-leader of the study.
"The associations we saw in our study between light exposure at night and obesity are very intriguing. We cannot yet tell at this stage what the reason for the associations is, but the results open up an interesting direction for research," Swerdlow said.
The findings were published in the American Journal of Epidemiology.