Deanna Arble, a scientist at Marquette University (Milwaukee, USA), is a circadian biologist studying the impact of exposure to environmental light. Struck by the time Portuguese people spend outside and its impact on health, this American scientist chose Portugal and the Center for Neuroscience and Cell Biology of the University of Coimbra to spend her fellowship.
For one year, Deanna will be in Portugal to study how environmental light exposure promotes healthy weight maintenance and even drives mitochondrial remodeling and thermogenesis. CNC-UC was a natural choice for Deanna, who collaborates with Paulo J. Oliveira’s lab and PAS GRAS project.
What was the question that sparked this study?
As a circadian biologist, our field has extensive evidence that environmental light has profound impacts on mental and physical wellbeing. During past visits to Portugal, I was struck by how much time people spend outside compared to my experience in the United States (US). Indeed, while seasonal light durations are pretty similar between the US and Portugal, US Americans spend about one third less time outside and, for almost every metric, the Portuguese are healthier than US Americans. I began to wonder: could this routine exposure to environmental light be providing health benefits to the Portuguese population?
And what is the main goal of this study?
The overarching objective is to determine the extent to which environmental light exposure promotes healthy weight maintenance and to identify the cellular mechanisms that underlie that relationship. To do that, the study has two integrated goals. First, we quantify how the timing and duration of natural outdoor light exposure relates to metabolic outcomes—such as BMI—in Southern European populations who routinely spend more time outside. Second, we ask whether those real-world light patterns leave a measurable imprint on cellular metabolism, using non‑invasively derived human stem cells to examine mitochondrial function and thermogenic programming.
Are there any preliminary results?
At this stage, we do not yet have results from this specific study, as the work is designed to be conducted during the Fulbright award period. However, the project is strongly anchored in prior evidence from my lab and others demonstrating that light affects physiology, metabolism, sympathetic tone, and energy balance.
How significant is this study in the context we live in? What are its impacts on the current social context?
Obesity is a global health challenge, and many existing treatments—medications, surgery, intensive lifestyle programs—are invasive, expensive, or difficult to sustain. What makes this study significant is that it focuses on using light as a modifiable and universally accessible environmental factor to mitigate obesity risks. If everyday light exposure meaningfully shapes metabolism, it reframes how we think about obesity prevention. It suggests that health is shaped not only by what we eat or how much we exercise, but also by our environmental structure and particularly exposure to natural daylight.
What new lines of research might this study open up?
This project opens several new directions. Mechanistically, it creates an entry point to study how light drives mitochondrial remodeling and thermogenesis. That’s a frontier area with implications well beyond obesity. It also establishes methodological links between wearable light measurements, population‑level behavior, and cellular readouts—tools that could be applied to sleep disorders, cardiometabolic disease, aging, and mental health.
Who are the partners in the project in which the study is embedded?
The study is a close collaboration between my laboratory at Marquette University (Milwaukee, Wiscounsin, USA) and Dr. Paulo J. Oliveira’s team at the University of Coimbra. More broadly, the human research component is integrated into PAS GRAS, a Horizon Europe–funded research consortium focused on obesity risk factors, which includes 16 partner institutions across Europe and the UK.
