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Reference topic 6: The Sitting Disease

Sitting too much: the health effects, and what actually helps

ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.58 sources7 graded recommendationsTopic hub: MovementTopic hub: Strength and bone

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In the years after the Second World War, a London double-decker bus carried two employees and, without anyone planning it, an experiment. The driver sat at the wheel. The conductor collected the fares, which meant climbing "up and down stairs 11 days a fortnight, 50 weeks a year, often for decades," as the man who noticed the difference later put it.1

That man was Jeremy Morris, known as Jerry, who ran the Medical Research Council's new social medicine unit in London.2 His team gathered sick-leave files, doctors' diagnoses and death certificates for about 31,000 London Transport men.345 The double-decker gave the cleanest comparison: two men on the same bus, one sitting, one climbing.

Mismatch card

The system

Leg muscles, bones and joints, and the blood-sugar control that working muscle provides.

What it expects

Hours of walking and carrying, and rest in postures (squatting, kneeling, ground-sitting) that keep leg muscles working.

What it gets

About 7.7 sedentary hours a day for the average American, and too little activity for nearly a third of adults worldwide.1213

What happens in the gap

Higher blood sugar after meals within hours; lost fitness within weeks; bone loss within months when loading stops, and lighter skeletons over millennia; higher mortality where long sitting meets low activity.

The handrail

A few minutes' walk every 20-30 minutes, 30-40 minutes a day of moderate-to-vigorous activity, and some rest on the floor or in a squat. (●●○)

Strength of evidence

●●○ Consistent short-term trials and large cohorts, but few long-term trials, and cohorts cannot fully separate sitting from inactivity.

What this topic covers

  • ·The Ancestral Way to Rest
  • ·What the Chair Switches Off
  • ·Bones That Remember Loading
  • ·The Lost Squat

The practical version is in the book: Chapter 3, The Body That Walks.

The handrail

Topic 40 holds the full movement program. For the chair itself:

Morris followed his own evidence. He jogged every day until his feet gave out. After that he swam daily, almost to the end of a life that ran to 99 years.258

Each recommendation carries the strength of the evidence behind it. How the grades work.

  1. Break up long sitting

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    Every 20-30 minutes, walk for 2-5 minutes; walking beats standing.151718 ●●○ (consistent short trials; long-term benefit unproven)

  2. Move enough to cancel the chair

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    About 30-40 minutes a day of moderate-to-vigorous activity (measured by motion sensor) weakens the link between long sitting and early death. By questionnaire, 60-75 minutes of moderate activity appears to erase it.4142 ●●○

  3. Take the stairs

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    Climbing more than five flights (about 50 steps) a day was associated with 16-23% lower risk of atherosclerotic cardiovascular disease (disease of clogged arteries) in 458,860 UK adults.52 ●●○ See a clinician first if stairs bring on chest pain or breathlessness, or if your balance is poor.

  4. Rest actively

    EmergingEvidence grade: Emerging. Early, small, animal-only, or actively contested.

    Sit on the floor, kneel or squat for short spells, holding a doorframe or using a low stool until your hips and ankles allow more.7 ●○○ With knee osteoarthritis, avoid long squatting; with a hip replacement, follow your surgeon's precautions on deep bending. Stop if it hurts.

  5. Load your bones, and carry things

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    In one randomized trial, 30 minutes of supervised high-intensity resistance and impact training twice a week for 8 months raised spine bone density 2.9% in postmenopausal women with low bone mass, while a gentle home program lost 1.2%.53 Walking alone is a weak bone signal.54 ●●○ Weighted-vest exercise helped bone in small trials, but the one study that isolated the vest found it added nothing for bone; everyday carrying is untested.55 ●○○ With osteoporosis or a past fragility fracture, start under supervision.

  6. Test yourself once or twice a year

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    In the sitting-rising test you sit down on the floor and stand up again, starting from 5 points for each movement and losing 1 for each hand or knee you use. Among 2,002 adults aged 51 to 80, scores of 0-3 carried 5.44 times the mortality of scores of 8-10, adjusted for age, sex and body-mass index.56 Treat a low score as a prompt to train strength, balance and mobility, not as a prognosis, and try it with something sturdy within reach if your balance is uncertain. ●●○ as a marker

  7. On the toilet

    EmergingEvidence grade: Emerging. Early, small, animal-only, or actively contested.

    a footstool is cheap and may help some people. Leave the phone outside: smartphone use there was associated with 46% higher odds of hemorrhoids in one study.394057 See a clinician about persistent constipation or bleeding. ●○○

The skeptic's corner

The case against this topic, from the research itself.

The chair's case is weaker than its reputation. The Hadza rest as long as industrialized people do, so sitting alone cannot be the whole story.7 In pooled data on more than a million people, those who sat more than eight hours a day but were highly active had no clear excess mortality. High levels of moderate activity, an hour or a little more a day, "seem to eliminate the increased risk of death associated with high sitting time," the authors concluded. Five or more hours of daily television, though, stayed linked to higher risk even in the most active.41 Motion-sensor studies point the same way.42

Other large studies pull both ways. Whitehall II followed thousands of British civil servants for well over a decade and found no link between sitting and mortality.43 In UK Biobank, a large British health study, more than 10.6 hours a day of sedentary time was associated with 45% higher risk of heart failure than 8.2 to 9.4 hours. The link held even among people who met activity guidelines.44 And sick people sit more, so observational studies (which watch people rather than test them) carry some reverse causation: illness can drive the sitting.

Then there is the slogan. "Sitting is more dangerous than smoking," the Mayo Clinic researcher James Levine told the Los Angeles Times.45 The comparison is not close. Against never-smokers, the heaviest smokers suffer more than 2,000 extra deaths per 100,000 people a year; the heaviest sitters, against the lightest, about 190.46 Lieberman calls equating the two "unhelpful."10

Standing is no cure either. It burns only about 0.15 kcal (food calories) a minute more than sitting.47 Beyond two hours a day, each extra half hour of it was associated with 11% higher risk of varicose veins and related problems.48 Sit-stand desks cut workplace sitting at first, on low-quality evidence, but the trials measured sitting, not disease.49 Squatting has a price, too: in Beijing, squatting two or more hours a day as a young adult was associated with about twice the odds of knee osteoarthritis.34 Nor is the chair a proven cause of low back pain, which affected 619 million people in 2020. A systematic review found "strong, consistent evidence" of no link with sitting at work (Topic 21).5051

Terms this topic defines

Related topics

Sources cited above

  1. 1.Morris, J.N. (2005). "Exercise versus heart attack: history of a hypothesis." In Coronary Heart Disease Epidemiology: From Etiology to Public Health, 2nd ed. Oxford University Press, 275-290. Quoted in Blackburn, H. "Jeremy Morris on Physical Activity and Coronary Disease." University of Minnesota, Heart Attack Prevention (essay). http://www.epi.umn.edu/cvdepi/essay/jeremy-morris-on-physical-activity-and-coronary-disease/
  2. 2.Royal College of Physicians (n.d.). Inspiring Physicians: Jeremy Noah Morris. https://history.rcp.ac.uk/inspiring-physicians/jeremy-noah-morris (Morris grew up in Glasgow)
  3. 3.Morris, J.N., Heady, J.A., Raffle, P.A.B., Roberts, C.G., and Parks, J.W. (1953). "Coronary heart-disease and physical activity of work." The Lancet, 262(6795), 1053-1057. https://doi.org/10.1016/S0140-6736(53)90665-5 (part 1); 262(6796), 1111-1120. https://doi.org/10.1016/S0140-6736(53)91495-0 (part 2). (the men were aged 35 to 64 and included drivers, conductors, motormen and Underground guards)
  4. 4.Blair, S.N., Davey Smith, G., Lee, I-M., et al. (2010). "A tribute to Professor Jeremiah Morris: the man who invented the field of physical activity epidemiology." Annals of Epidemiology, 20(9), 651-660. https://doi.org/10.1016/j.annepidem.2010.06.001. Incidence rates (age-standardized, 1949-1952) from its Table 1, reproduced from Blair, S.N. and Morris, J.N. (2009). "Healthy hearts, and the universal benefits of being physically active: physical activity and health." Annals of Epidemiology, 19(4), 253-256. https://doi.org/10.1016/j.annepidem.2009.01.019. The 2004 remark is quoted from Davey Smith, G. (2004). "A conversation with Jerry Morris." Epidemiology, 15, 770-773. (coronary heart disease: 1.9 cases per 1,000 men a year in conductors against 2.7 in drivers; sudden death: 0.5 per 1,000 against 1.1; Morris disliked the uniforms paper's subtitle, "epidemiology of uniforms")
  5. 5.Morris et al. (1953), part 2, as quoted in University of Minnesota, Heart Attack Prevention, "London Transport Workers Study" (study synopsis). http://www.epi.umn.edu/cvdepi/study-synopsis/london-transport-workers-study/
  6. 7.Raichlen, D.A., Pontzer, H., Zderic, T.W., Harris, J.A., et al. (2020). "Sitting, squatting, and the evolutionary biology of human inactivity." PNAS, 117(13), 7115-7121. https://doi.org/10.1073/pnas.1911868117 (28 adults at Sengeli camp, Tanzania, wore thigh accelerometers for 8 days; of observed resting time, about 18% was spent squatting and about 12.5% kneeling; the hypothesis in the authors' words: human physiology is "likely adapted to more consistently active muscles derived from both physical activity and from nonambulatory postures with higher levels of muscle contraction")
  7. 41.Ekelund, U., Steene-Johannessen, J., Brown, W.J., Fagerland, M.W., et al. (2016). "Does physical activity attenuate, or even eliminate, the detrimental association of sitting time with mortality? A harmonised meta-analysis of data from more than 1 million men and women." The Lancet, 388(10051), 1302-1310. https://doi.org/10.1016/S0140-6736(16)30370-1 (high sitting meant over 8 hours a day; people who sat under 4 hours but were among the least active had 27% higher mortality than equally light sitters who were the most active; high activity meant about 60-75 minutes a day of moderate activity, measured by questionnaire)
  8. 42.Ekelund, U., Tarp, J., Fagerland, M.W., et al. (2020). "Joint associations of accelerometer-measured physical activity and sedentary time with all-cause mortality: a harmonised meta-analysis in more than 44 000 middle-aged and older individuals." British Journal of Sports Medicine, 54(24), 1499-1506. https://doi.org/10.1136/bjsports-2020-103270 (by accelerometer, 30-40 minutes a day of moderate-to-vigorous activity weakened the link between sitting and mortality)
  9. 43.Pulsford, R.M., Stamatakis, E., Britton, A.R., Brunner, E.J., et al. (2015). "Associations of sitting behaviours with all-cause mortality over a 16-year follow-up: the Whitehall II study." International Journal of Epidemiology, 44(6), 1909-1916. https://doi.org/10.1093/ije/dyv191 (5,132 civil servants followed for about 16 years)
  10. 44.Ajufo, E., Kany, S., Rämö, J.T., Churchill, T.W., et al. (2025). "Accelerometer-measured sedentary behavior and risk of future cardiovascular disease." Journal of the American College of Cardiology, 85(5), 473-486. https://doi.org/10.1016/j.jacc.2024.10.065
  11. 45.MacVean, M. (2014, 31 July). "'Get Up!' or lose hours of your life every day, scientist says." Los Angeles Times. https://www.latimes.com/science/sciencenow/la-sci-sn-get-up-20140731-story.html (interview published in 2014)
  12. 46.Vallance, J.K., Gardiner, P.A., Lynch, B.M., D'Silva, A., et al. (2018). "Evaluating the evidence on sitting, smoking, and health: is sitting really the new smoking?" American Journal of Public Health, 108(11), 1478-1482. https://doi.org/10.2105/AJPH.2018.304649
  13. 10.Siliezar, J. (2021, 4 January). "Why run unless something is chasing you?" Harvard Gazette. Interview with Daniel Lieberman about his book Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding (Pantheon, 2021). https://news.harvard.edu/gazette/story/2021/01/daniel-lieberman-busts-exercising-myths/
  14. 47.Saeidifard, F., Medina-Inojosa, J.R., Supervia, M., Olson, T.P., et al. (2018). "Differences of energy expenditure while sitting versus standing: a systematic review and meta-analysis." European Journal of Preventive Cardiology, 25(5), 522-538. https://doi.org/10.1177/2047487317752186
  15. 48.Ahmadi, M.N., Coenen, P., Straker, L., and Stamatakis, E. (2024). "Device-measured stationary behaviour and cardiovascular and orthostatic circulatory disease incidence." International Journal of Epidemiology, 53(6), dyae136. https://doi.org/10.1093/ije/dyae136
  16. 49.Shrestha, N., Kukkonen-Harjula, K.T., Verbeek, J.H., Ijaz, S., et al. (2018). "Workplace interventions for reducing sitting at work." Cochrane Database of Systematic Reviews, 12, CD010912. https://doi.org/10.1002/14651858.CD010912.pub5 (about 100 minutes a workday at first)
  17. 34.Zhang, Y., Hunter, D.J., Nevitt, M.C., Xu, L., et al. (2004). "Association of squatting with increased prevalence of radiographic tibiofemoral knee osteoarthritis: the Beijing Osteoarthritis Study." Arthritis and Rheumatism, 50(4), 1187-1192. https://doi.org/10.1002/art.20127 (about 40% of men and 68% of women aged 60 and over recalled squatting an hour or more a day at age 25; the knee finding was for 2 or more hours a day at age 25)
  18. 50.GBD 2021 Low Back Pain Collaborators (2023). "Global, regional, and national burden of low back pain, 1990-2020, its attributable risk factors, and projections to 2050: a systematic analysis of the Global Burden of Disease Study 2021." The Lancet Rheumatology, 5(6), e316-e329. https://doi.org/10.1016/S2665-9913(23)00098-X
  19. 51.Roffey, D.M., Wai, E.K., Bishop, P., Kwon, B.K., et al. (2010). "Causal assessment of occupational sitting and low back pain: results of a systematic review." The Spine Journal, 10(3), 252-261. https://doi.org/10.1016/j.spinee.2009.12.005
  20. 58.Lange, K.W. (2024). "Jeremy Morris as a pioneer of behavioural epidemiology, social medicine and public health." Scandinavian Journal of Public Health, 52(8), 1026-1027. https://doi.org/10.1177/14034948231218313 (published online 2023).
  21. 15.Dunstan, D.W., Kingwell, B.A., Larsen, R., Healy, G.N., et al. (2012). "Breaking up prolonged sitting reduces postprandial glucose and insulin responses." Diabetes Care, 35(5), 976-983. https://doi.org/10.2337/dc11-1931 (19 adults aged 45 to 65; after the drink they sat for 5 hours, or broke up sitting every 20 minutes with 2 minutes of light (3.2 km/h, 2 mph) or moderate walking; light walking cut the glucose response by 24.1% and moderate walking by 29.6%; both cut the insulin response by about 23%)
  22. 17.Buffey, A.J., Herring, M.P., Langley, C.K., Donnelly, A.E., et al. (2022). "The acute effects of interrupting prolonged sitting time in adults with standing and light-intensity walking on biomarkers of cardiometabolic health in adults: a systematic review and meta-analysis." Sports Medicine, 52(8), 1765-1787. https://doi.org/10.1007/s40279-022-01649-4
  23. 18.Duran, A.T., Friel, C.P., Serafini, M.A., Ensari, I., et al. (2023). "Breaking up prolonged sitting to improve cardiometabolic risk: dose-response analysis of a randomized crossover trial." Medicine and Science in Sports and Exercise, 55(5), 847-855. https://doi.org/10.1249/MSS.0000000000003109 (2023 dose-finding trial; 11 middle-aged and older adults; 5 minutes of easy walking every 30 minutes over an 8-hour day)
  24. 52.Song, Z., Wan, L., Wang, W., Li, Y., et al. (2023). "Daily stair climbing, disease susceptibility, and risk of atherosclerotic cardiovascular disease: a prospective cohort study." Atherosclerosis, 386, 117300. https://doi.org/10.1016/j.atherosclerosis.2023.117300
  25. 53.Watson, S.L., Weeks, B.K., Weis, L.J., Harding, A.T., et al. (2018). "High-intensity resistance and impact training improves bone mineral density and physical function in postmenopausal women with osteopenia and osteoporosis: the LIFTMOR randomized controlled trial." Journal of Bone and Mineral Research, 33(2), 211-220. https://doi.org/10.1002/jbmr.3284
  26. 54.Ma, D., Wu, L., and He, Z. (2013). "Effects of walking on the preservation of bone mineral density in perimenopausal and postmenopausal women: a systematic review and meta-analysis." Menopause, 20(11), 1216-1226. https://doi.org/10.1097/GME.0000000000000100
  27. 55.Wang, X., Zhou, L., Shi, T., et al. (2026). "Effects of weighted vest on bone health and body fat in middle-aged and older adults: a systematic review and meta-analysis." Osteoporosis International, published online. https://doi.org/10.1007/s00198-026-08196-y
  28. 56.Brito, L.B., Ricardo, D.R., Araújo, D.S., Ramos, P.S., et al. (2014). "Ability to sit and rise from the floor as a predictor of all-cause mortality." European Journal of Preventive Cardiology, 21(7), 892-898. https://doi.org/10.1177/2047487312471759 (published online December 2012).
  29. 39.Modi, R.M., Hinton, A., Pinkhas, D., Groce, R., et al. (2019). "Implementation of a defecation posture modification device: impact on bowel movement patterns in healthy subjects." Journal of Clinical Gastroenterology, 53(3), 216-219. https://doi.org/10.1097/MCG.0000000000001143 (52 healthy volunteers)
  30. 40.Trieu, R.Q., Prott, G., Sequeira, C., Jones, M., et al. (2023). "Using a footstool does not aid simulated defecation in undifferentiated constipation: a randomized trial." Neurogastroenterology and Motility, 35(7), e14580. https://doi.org/10.1111/nmo.14580 (41 people with constipation; the simulated bowel movement was expelling a small balloon)
  31. 57.Ramprasad, C., Wu, C., Chang, J., Rangan, V., et al. (2025). "Smartphone use on the toilet and the risk of hemorrhoids." PLoS ONE, 20(9), e0329983. https://doi.org/10.1371/journal.pone.0329983
  32. 12.Matthews, C.E., Chen, K.Y., Freedson, P.S., Buchowski, M.S., et al. (2008). "Amount of time spent in sedentary behaviors in the United States, 2003-2004." American Journal of Epidemiology, 167(7), 875-881. https://doi.org/10.1093/aje/kwm390 (6,329 Americans aged 6 and older, 2003-2004; 54.9% of monitored time)
  33. 13.Strain, T., Flaxman, S., Guthold, R., Semenova, E., et al. (2024). "National, regional, and global trends in insufficient physical activity among adults from 2000 to 2022: a pooled analysis of 507 population-based surveys with 5.7 million participants." The Lancet Global Health, 12(8), e1232-e1243. https://doi.org/10.1016/S2214-109X(24)00150-5. The figure of about 1.8 billion people is from World Health Organization (2024, 26 June), news release. https://www.who.int/news/item/26-06-2024-nearly-1.8-billion-adults-at-risk-of-disease-from-not-doing-enough-physical-activity (31.3% of adults in 2022, up from 23.4% in 2000)

This topic carries 58 notes in the research manuscript; the 33 above are those behind the material on this page. Full source register.