What sitting all day does to the body

For decades, one of the most prominent public health messages has been that smoking kills. But another everyday habit, far less dramatic and far more socially acceptable, may also be damaging our health: prolonged sitting.

Many people now spend up to ten hours a day seated at desks, in meetings or in front of screens. It may feel harmless, even unavoidable, but growing evidence suggests that too much sitting is linked to serious health risks, including cardiovascular disease, type 2 diabetes and early death.

People are often told to protect their health by exercising more and eating better. That advice matters, but it misses something important. Even those who meet recommended exercise targets may still face increased health risks if they spend most of the day sitting down.

This is because sedentary behaviour and physical inactivity are not the same thing. Physical inactivity means not doing enough moderate or vigorous exercise. Public health guidelines recommend at least 150 minutes of moderate activity a week, such as brisk walking or cycling, or 75 minutes of vigorous activity, such as running. Sedentary behaviour, by contrast, refers to long periods of sitting or reclining with very low energy expenditure, whether at a desk, in front of the television or during a long commute.

A person can therefore be physically active and still highly sedentary. Someone might go for a run before work, then remain seated for most of the next eight hours. The exercise helps, but it does not erase the effects of prolonged sitting on the body.

When the body stays still for long periods, a series of changes begins to take place. Skeletal muscle activity drops, making it harder for the body to absorb glucose from the blood. Over time, this contributes to insulin resistance, a major pathway to type 2 diabetes. Fat metabolism also slows down.

Blood flow becomes less efficient, reducing the delivery of oxygen and nutrients to tissues. This can impair vascular function and, over time, contribute to raised blood pressure.

Together, these metabolic and circulatory changes increase the risk of cardiometabolic problems, including high blood sugar, unhealthy cholesterol levels and the accumulation of abdominal fat.

Prolonged sitting also affects the musculoskeletal system. Poor posture and limited movement place strain on the neck, shoulders and lower back, helping to explain the aches and pains so common among office workers.

The effects are not only physical. Long periods of inactivity can reduce alertness, concentration and energy levels. Employees who sit for extended periods often report feeling more sluggish and less productive.

Globally, physical inactivity is estimated to contribute to around four to five million deaths each year. Much of the public health response has focused on encouraging people to exercise more, but reducing sedentary time is increasingly recognised as an important goal in its own right.

Since most adults spend a large share of their waking hours at work, the workplace is one of the most important settings for tackling the problem. Offices, universities and hospitals are not just places of productivity. They are also environments in which daily habits are shaped and reinforced.

Reducing sitting time does not require a gym membership or a dramatic office overhaul. Small, regular interruptions to sitting can make a meaningful difference.

Research suggests that standing up or moving for just two to five minutes every 30 to 60 minutes can improve glucose metabolism and reduce cardiometabolic risk.

Some organisations are already trying to build this into the working day. Walking meetings, prompts to stand or stretch and short movement breaks between tasks can all help people spend less time sitting.

Workplace design matters too. Height-adjustable desks allow employees to alternate between sitting and standing, while accessible staircases and walking routes can encourage more movement throughout the day.

A study of offices in the UK found that these kinds of measures can reduce daily sitting time by around one to one and a half hours. Employees also reported improvements in energy, focus and musculoskeletal comfort.

The message is straightforward: regular exercise is essential, but it does not fully offset the risks of sitting for too long. If smoking forced us to rethink the environments in which we worked and socialised, prolonged sitting should force us to rethink the structure of the working day itself. A short walk at lunch, standing during a phone call or simply getting up between meetings may sound like trivial adjustments. They are not. For modern workers, protecting health is not only about moving more before or after work. It is also about sitting less while work is happening.

Samina Akhtar has received funding from the Health Research Institute, National Institutes of Health, Islamabad, Pakistan. She is also a sub-recipient of a grant from the Fogarty International Center of the National Institutes of Health (USA) supporting her PhD research.