Walking in the Light: How History of Physical Activity, Sunlight, and Vitamin D Account for Body Fat—A UK Biobank Study

Abstract

Objective: The high prevalence of vitamin D deficiency and obesity drives the need for successful strategies that elevate vitamin D levels, prevent adipogenesis, and stimulate lipolysis. This study provides a theoretical model to evaluate how physical activity (PA) and sunlight exposure influence serum vitamin D levels and regional adiposity. This study hypothesized a posteriori that sunlight is associated with undifferentiated visceral adiposity by increasing the ratio of brown to white adipose tissue. Methods: Using 10-year longitudinal data, accelerometry, a sun-exposure questionnaire, and regional adiposity quantified by dual-energy x-ray absorptiometry imaging, a structural-equation mediation model of growth curves was constructed with a data-driven methodology. Results: Sunlight and PA conjointly increased serum vitamin D. Changes in vitamin D levels partially mediated how sunlight and PA impacted adiposity in visceral and subcutaneous regions within a subjective PA model. In an objective PA model, vitamin D was a mediator for subcutaneous regions only. Interestingly, sunlight was associated with less adiposity in subcutaneous regions but greater adiposity in visceral regions. Conclusions: Sunlight and PA may increase vitamin D levels. For the first time, this study characterizes a positive association between sunlight and visceral adiposity. Further investigation and experimentation are necessary to clarify the physiological role of sunlight exposure on adipose tissue.

Time spent in outdoor light is associated with increased blood pressure, higher hypertension risk, and lower hypotension risk

“…All these behavioral lifestyle and family history factors were associated with BP. As MET 18 , BMI 19 , and sleep duration 12 were associated with light exposure, they were included as potential mediators, and the remaining behavioral lifestyle and family history factors were included as effect modifiers. In the cross-sectional design, linear regression models were used to estimate the associations (βs) of light exposure with BP, and logistic regression models were used to estimate the associations (odds ratios, ORs) of light exposure with hypertension and hypotension.…”

“…All these behavioral lifestyle and family history factors were associated with BP. As MET 18 , BMI 19 , and sleep duration 12 were associated with light exposure, they were included as potential mediators, and the remaining behavioral lifestyle and family history factors were included as effect modifiers.…”