Non-Exercise Activity (NEAT)

Non-exercise activity thermogenesis, or NEAT, is the energy you burn in all the movement that isn't formal exercise: walking around at work, standing, chores, fidgeting. Between two people of the same size it can differ by up to about 2,000 kcal a day, and in a classic overfeeding study, changes in it closely tracked who resisted putting on fat. What it does for long-term health is inferred, not tested in trials.

Treat everyday movement as a lever in its own right: walk where you can, take calls on your feet, keep your step count up as you age, and let yourself fidget.

What it is

NEAT covers the energy spent on all physical activity that isn't structured exercise, sleeping or eating: walking as part of your job, standing, household chores, yard work, playing music, fidgeting. Its easiest-to-measure part is the daily step count.

How big the lever is

Two adults of the same body size can differ by up to about 2,000 kcal a day in NEAT, depending on their jobs and habits.^[1]

One way to see the size is the physical activity level: total daily energy use divided by basal metabolic rate, the energy you burn at complete rest. Across a whole day:

Lifestyle	Daily energy use, as a multiple of resting
Standing work	about 1.8–1.9
Seated work, little chance to move around, little strenuous activity outside work	about 1.4–1.5
Chair- or bed-bound	about 1.2

These are whole-day ratios, not the intensity of any one activity. The gap between the standing worker and the desk worker is roughly a quarter of daily energy use, which adds up over a year.^[2]

It falls with age

Older adults do roughly 29% less non-exercise activity than younger ones, which works out to about 5 km less incidental walking a day.^[3] This drop is separate from any change in formal exercise habits.

The overfeeding study

In a classic experiment, 16 volunteers without obesity were fed 1,000 kcal a day above what they needed to hold their weight, for eight weeks. How much of the extra energy they stored as fat varied ten-fold between people, and the paper reports that changes in NEAT accounted for those differences, directly predicting who resisted fat gain. Two-thirds of the rise in their daily energy use came from NEAT rather than from any deliberate exercise.^[4] It was a small, short study from 1999, with no long-term health outcomes.

Fidgeting

Fidgeting, restlessness and shifting position are part of NEAT. The same researcher has argued, in a hypothesis piece without new data, that modern chair-based environments override an innate human drive to move, calling it the "Fidget Factor".^[5]

There is a small trial behind the idea. In a randomised crossover trial in 20 adults with obesity, leg fidgeting through a three-hour sitting period after a glucose drink lowered both blood sugar and insulin, and increased blood flow through the arteries of the moving leg; the bigger the rise in blood flow, the bigger the drop in blood sugar.^[6] It measured a few hours, not long-term health.

What isn't known

The energy measurements are solid. The step from NEAT to longer life or less disease is an inference from them and from the sitting studies, not something a trial has tested. Sitting covers what long periods of stillness are linked to, and how to break them up.

What to do

Count everyday movement. Walking calls, stairs and errands on foot are part of your daily energy budget, not a footnote to the gym.
Fidget freely. It costs nothing, and in a small trial it helped blood-sugar handling.
Watch the age drift. Incidental walking tends to fall with age; a step target such as about 7,000 a day keeps an eye on it.