The benefits of time outside, and how much is enough

Time outside is linked with better health and mood, and the clearest number comes from a study of nearly 20,000 adults in England: people who had spent at least 120 minutes in nature in the past week were more likely to report good health and high well-being than people who had spent none, with the benefit leveling off between 200 and 300 minutes. It is an association, not proof, but it gives a usable target: about two hours a week, in any pattern. Daylight outdoors also sets the body clock, and going out is the simplest answer to a cue: leave the room, leave the house, walk.

What studies found about time in nature#

The 120-minute study, by White and colleagues, used a national survey that asked people about time spent in parks, canals and nature areas, on the coast and beaches, and in the countryside, not counting routine shopping trips or their own garden. Three findings matter. The benefit started at about 120 minutes a week. It peaked between 200 and 300 minutes, with no further gain. And it did not matter how the 120 minutes came: one long visit or several short ones worked the same. The pattern held for older adults and for people with long-term health problems.

The authors are careful about what it cannot show. The data are a snapshot, so they cannot rule out that healthier, happier people simply go outside more, and time in nature explained only a small share of the variation in health and well-being. They said it was too early for formal guidance.

Other work points the same way, with similar caveats:

• A review of 143 studies found that more exposure to greenspace was associated with lower cortisol, heart rate and diastolic blood pressure, and better self-reported health. Several of the pooled results were limited by poor study quality and high heterogeneity.
• An experiment on rumination, the loop of repetitive negative thought, sent healthy volunteers on a 90-minute walk. A walk through a natural area reduced rumination and activity in a brain region linked to it. The same length of walk in an urban setting did not.
• A pooled analysis of 10 UK studies with 1,252 people found that short spells of activity in green places gave the biggest gains in mood and self-esteem, with smaller returns after that. The largest effect on self-esteem came from five minutes. Every green setting helped, and places with water helped more.

Daylight and the body clock#

The body's master clock is set by light reaching the eyes, and the light outdoors is in a different league from the light indoors: up to 100,000 lux in direct sun and 25,000 lux in full daylight, against about 500 lux in a standard office. An expert consensus on lighting notes that indoor lighting standards set levels typically at least ten times below the natural light outside.

When researchers compared people's normal lives with a stretch of camping under natural light only, modern life meant less sunlight by day, more light after sunset, and a later body clock. Under natural light alone, the internal night began around sunset and ended just after sunrise.

Daylight shows up in mood and sleep too. In more than 400,000 UK Biobank participants, people spent a median of 2.5 daylight hours outdoors a day, and each extra hour was associated with lower odds of depression and low mood, less frequent tiredness, easier getting up and fewer insomnia symptoms. Again, an association, though the later follow-up pointed the same way, with smaller effects.

The same consensus recommends bright light through the day and dim light for at least the 3 hours before bed. A morning walk is the cheapest bright light there is; for the evening half, see how to sleep better. Daylight on skin is a separate matter, covered in sunlight and vitamin D.

Outside as the answer to a cue#

Of everything on this page, this is the part I would keep. A cue is usually a state you want to leave: bored, restless, lonely, tired in the wrong way. Many of them arrive indoors, alone, near a screen. Going outside changes the room, the light and the body's state in one move, before an urge has formed. It is the cheapest cue answer there is.

So the move is plain. Leave the room. If that is not enough, leave the house. Walk, with the phone in a pocket rather than a hand. It is the first step in what to do when an urge hits for a reason. If an urge still comes, walking is a good way to watch it rise and fall until it passes, which is what urge surfing means. Nothing here asks you to fight it.

How to get outside in a city#

Use what is near#

The 120-minute study counted parks, canals and nature areas, and it found several short visits worked as well as one long one. A city park, a canal or river path, or a nature area at the edge of town all count. If there is water nearby, use it.

Attach it to something you already do#

Walk part of the commute. Get off a stop early. Take phone calls walking. Eat lunch outside. A habit attached to an existing one needs no separate decision, and if the walk is brisk, it counts toward the week's exercise too.

Start with the morning#

Ten minutes outside in the first hour after waking is the practice in the body. It is the easiest daily dose to keep, and it is the light the body clock reads.

How to get outside in winter#

Winter is when getting out is hardest. The NHS advice for seasonal low mood is to get as much natural daylight as you can and to go outside in the daytime every day. Short days mean the window is narrow, so plan the walk for when there is light, which may mean lunchtime.

Dress for the weather rather than waiting for it to change. A short walk in the cold still counts toward the week.

If winter brings low mood that lasts, see a doctor. The NHS notes that the evidence for light boxes is uncertain, and it advises talking to a doctor before using one, because they may not suit people with some eye conditions or on some medicines.

Questions people ask#

How much time outside do you need a day?#

There is no official daily figure. The England study points to about 120 minutes a week, which is roughly 17 minutes a day, with gains leveling off between 200 and 300 minutes.

Does sitting by a window count?#

Not in these studies, which measured time actually spent outdoors. For vitamin D, a window does nothing, because UVB does not pass through glass.

Does it have to be green space?#

For the body clock, what counts is daylight, green or not. For mood, nature seems to add something: in the rumination experiment a walk in nature helped and an urban walk did not, and in the pooled UK studies places with water helped most.

Getting outside will not end a habit on its own, and nothing on this page claims it will. What it does is make the hard hours easier to leave, and that is where the habit is broken. Stop completely, decided once, and use the door when the cue comes. Thirty days is the plan.