Nearly half of Americans spend less than two hours outdoors in an entire week, according to a new national survey from the Nature & Health Alliance involving researchers at Texas A&M University. That finding sits at the center of a warning from Dr. John La Puma, a California physician and expert in nature-based medicine, who argues that modern life inside buildings carries what he calls a hidden health tax.
In his book «Indoor Epidemic», La Puma notes that humans now spend roughly 93% of their lives indoors. The remedy he proposes is not a drug or a device but a simple shift in routine: a 7% outdoor prescription, built around intentional time outside.
La Puma told Fox News Digital that many patients arrive at his office exhausted despite sleeping through the night, relying on coffee to feel normal, crashing in the afternoon and feeling wired at night even when their lab results look fine. He attributes the pattern to what he calls the four Bs, a cluster of problems tied to life spent mostly inside.
The first is the body clock. Outdoor light can be many times brighter than typical indoor lighting, La Puma said, making it a powerful signal for setting the circadian rhythm. Without that signal, he explained, the body does not know what time it is and falls asleep whenever it can rather than on time. Bright outdoor light soon after waking helps synchronize the sleep-wake cycle and supports the natural rise in melatonin later in the evening. He recommends about 10 minutes outdoors within the first hour of waking, without sunglasses.
The second is what La Puma calls ultraprocessed time, hours lost to screens, scrolling and other digital distractions. He compares it to ultraprocessed food: not nutritious, synthetic, artificial and ubiquitous. Because people often use the same devices for work, entertainment and relaxation, the body may not interpret screen time as true rest or escape.
He also points to a third problem: people are horizon-deprived. Indoors, he said, we cannot see more than about 20 feet in front of us, and the eyes lose the chance to focus at distance. His advice is to get up every hour, go to a window and look outside for a minute. That, he said, relaxes the eyes and the muscles around the temples, reduces headaches, improves energy and reduces fatigue — the beginning of reversing burnout.
The fourth is air quality. People who spend the day indoors may feel mentally foggy by the afternoon, particularly in poorly ventilated spaces where carbon dioxide can build up above 1,000 parts per million. Some research has linked elevated indoor CO2 with reduced cognitive performance. La Puma said the fog is not simply a matter of bad decisions but has a biologic reason, and he recommends cross-ventilation where possible, though that is difficult in many offices and conference rooms. The Environmental Protection Agency notes that concentrations of some pollutants can be two to five times higher indoors than outdoors.
Disrupted body clocks also affect cortisol, the hormone that naturally rises and falls through the day. La Puma said an out-of-sync clock can disturb that rhythm, and research has linked altered cortisol activity with greater abdominal and visceral fat, though the relationship is complex. Getting daylight early in the morning, he said, produces the cortisol bump that helps a person feel awake, followed by an appropriate drop later.
Most people already spend about an hour outdoors daily, walking from a car to an office or between errands, but La Puma calls that incidental time rather than biologically active time. To counter the four Bs, he recommends intentional time outdoors in a blue or green space for a minimum effective dose of 17 minutes a day. For city dwellers who cannot see the sky, he suggests looking at a distant rooftop or through an open window, with the goal of focusing beyond the confines of an indoor space.
«So 17 minutes a day is the minimum effective dose — that's all it takes to begin to bend the curve on the four Bs,» he said. «You can turn those minutes into medicine.»