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Impacts: Health impacts

Health impacts of obesity: an overview

Last updated 22-05-2025

Obesity is a major risk factor for various diseases including cardiovascular disease, Type 2 diabetes, chronic kidney disease, liver disease, at least 13 types of cancer and dementia.

Key Evidence

01

Blood pressure increases in line with Body Mass Index (BMI)

02

Excess weight is associated with a higher risk of disability in older age

03

Risk of death increases in line with the number of years lived with obesity

The human body attempts to maintain energy balance and stable body weight through complex neurohormonal feedback systems that regulate energy intake and expenditure. Energy balance cannot be maintained, however, when there is a large surplus of energy over a prolonged period of time, and this will lead to weight gain.123

It is important to recognise that obesity is not simply caused by an imbalance of energy intake and expenditure. It is the result of an interaction between several factors including genetic, physiological, behavioural and social drivers, as well as environmental factors including widespread availability of highly processed unhealthy foods.123

Obesity is associated with a state of low grade, chronic inflammation and an elevated risk for several diseases

Obesity is associated with a state of low grade, chronic inflammation and an elevated risk for several diseases.23 It increases the risk of developing Type 2 diabetes, in which the body does not properly produce or use insulin, a hormone that regulates blood glucose levels and helps move glucose from the blood into the body’s cells for energy.45 Glucose therefore builds up in the blood, which can result in serious complications including damage to the kidneys and eyes, and heart disease and stroke.6 High blood glucose levels can also result in circulation problems (peripheral vascular disease) and nerve damage (peripheral neuropathy), which can cause foot ulcers and skin infections.6

Excess weight is directly linked to various cardiovascular risk factors.78 As BMI increases, so does blood pressure, atherosclerosis (a build up of fats, cholesterol and other substances in arteries, that can lead to heart attack and stroke) and blood glucose. This translates into increased risk for coronary heart disease, stroke and cardiovascular death.78

Musculoskeletal disorders including osteoarthritis and low back pain are associated with excess weight, due to inflammation.91011121314 Excess weight is associated with a higher risk of future disability in older age, with an Australian study finding a graded relationship between BMI and measures of disability including difficulties with bathing, dressing, eating, getting out or a chair or bed, using the toilet and walking about 200 metres.15

Excess weight has a direct impact on the development and progression of chronic kidney disease (CKD).1617The kidneys have to work harder to filter more blood than normal to meet the metabolic demands of increased body weight and this can damage the kidneys, heightening the risk of developing CKD in the long-term.1617 Diabetes and high blood pressure, also linked to overweight and obesity, are major risk factors for CKD.17

Obesity is strongly linked with respiratory symptoms and diseases including asthma, chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea, due to its physical effects (for example, weight gain is associated with decreases in lung volumes) and systemic inflammation.18

There appears to be a strong association between obesity and both infection with COVID-19 and severity of outcomes for those infected. An ‘umbrella’ review, which synthesised the results of 52 published reviews and 49 meta-analyses on the relationship between excess weight and COVID-19,19 found consistent associations between excess weight and; infection with COVID-19, severity of COVID-19, hospitalisation for COVID-19, and mortality from COVID-19. Overall, the authors concluded that there was a broadly linear association between excess weight and COVID-19 outcomes.19 Notably, however, the synthesis found very few of the included reviews were of high quality, and there was comparatively limited evidence exploring how factors such as ethnicity, socio-economic status, geography and comorbidities may moderate the association between excess weight and COVID-19 outcomes.19 Excess weight is associated with an increased risk of non-alcoholic fatty liver disease (NAFLD), which is when fat tissue builds up in the liver.20 In time, this accumulation of fat can cause inflammation and the formation of scar tissue, in a condition called non-alcoholic steatohepatitis (NASH).20 NASH can then lead to cirrhosis of the liver, a type of liver damage where healthy cells are replaced by scar tissue.21 In a state of cirrhosis, the liver is unable to perform its vital functions of metabolism, production of proteins including blood clotting factors, and filtering of drugs and toxins.21

Excess weight can lead to cancer as a result of metabolic and hormonal changes and chronic inflammation that may cause the body to produce abnormal cells.22 The International Agency for Research on Cancer has linked overweight and obesity to at least 13 different types of cancer. These are: colorectal; uterine; kidney; breast cancer in postmenopausal women; adenocarcinoma of the oesophagus; liver; gallbladder; pancreas; thyroid; ovary; gastric cardia (part of the stomach); multiple myeloma (a blood cancer) and meningioma (a type of brain tumour).23

Obesity is a risk factor for dementia and Alzheimer’s Disease24, which may be due to inflammation, insulin resistance and cellular stress in areas of the brain thought to be involved in progression of the disease.2526 Obesity is also linked to depression with the results of a major Australian diabetes, obesity and lifestyle study finding that depression was nearly twice as common among people with obesity compared to those who did not have obesity27, however the direction of causality is not clear.

Researchers have found that the risk of mortality increases in line with the number of years lived with obesity.28 This is an important consideration when considering the population health burden associated with obesity, which is increasingly being seen in younger age groups.28 Researchers have found a continuous increase in the risk of death associated with a BMI of more than 25,29 showing that overweight and moderate obesity – and not just severe obesity – are associated with higher mortality.30

Content for this page was reviewed and updated by Melanie Nichols at GLOBE, Institute for Health Transformation, Deakin University. For more information about the approach to content on the site please see About | Obesity Evidence Hub.

References

1. National Health and Medical Research Council. Clinical practice guidelines for the management of overweight and obesity in adults, adolescents and children in Australia. Melbourne 2013. Available from: https://www.nhmrc.gov.au/...
2. Lingvay I, Cohen RV, Roux CWl, Sumithran P. Obesity in adults. The Lancet. 2024;404(10456):972-987. doi:10.1016/S0140-6736(24)01210-8
3. Elmaleh-Sachs A, Schwartz JL, Bramante CT, Nicklas JM, Gudzune KA, Jay M. Obesity Management in Adults: A Review. JAMA. 2023;330(20):2000-2015. doi:10.1001/jama.2023.1989
4. Ruze R, Liu T, Zou X, et al. Obesity and type 2 diabetes mellitus: connections in epidemiology, pathogenesis, and treatments. Review. Frontiers in Endocrinology. 2023-April-21 2023;14doi:10.3389/fendo.2023.1161521
5. Klein S, Gastaldelli A, Yki-Järvinen H, Scherer PE. Why does obesity cause diabetes? Cell Metab. Jan 4 2022;34(1):11-20. doi:10.1016/j.cmet.2021.12.012
6. DeFronzo RA, Ferrannini E, Groop L, et al. Type 2 diabetes mellitus. Nature Reviews Disease Primers. 2015/07/23 2015;1(1):15019. doi:10.1038/nrdp.2015.19
7. Koliaki C, Liatis S, Kokkinos A. Obesity and cardiovascular disease: revisiting an old relationship. Metabolism. 2019/03/01/ 2019;92:98-107.
8. Valenzuela PL, Carrera-Bastos P, Castillo-García A, Lieberman DE, Santos-Lozano A, Lucia A. Obesity and the risk of cardiometabolic diseases. Nature Reviews Cardiology. 2023/07/01 2023;20(7):475-494. doi:10.1038/s41569-023-00847-5
9. Binvignat M, Sellam J, Berenbaum F, Felson DT. The role of obesity and adipose tissue dysfunction in osteoarthritis pain. Nature Reviews Rheumatology. 2024/09/01 2024;20(9):565-584. doi:10.1038/s41584-024-01143-3
10. Walsh TP, Arnold JB, Evans AM, Yaxley A, Damarell RA, Shanahan EM. The association between body fat and musculoskeletal pain: a systematic review and meta-analysis. BMC Musculoskelet Disord. Jul 18 2018;19(1):233. doi:10.1186/s12891-018-2137-0
11. Corrado A, Guadagni I, Picarelli G, Variola A. Obesity and Chronic Inflammation: Implications for Rheumatoid Arthritis, Spondyloarthritis, and Ulcerative Colitis. Immunity, Inflammation and Disease. 2025;13(1):e70080. doi:https://doi.org/10.1002/iid3.70080
12. Nedunchezhiyan U, Varughese I, Sun AR, Wu X, Crawford R, Prasadam I. Obesity, Inflammation, and Immune System in Osteoarthritis. Review. Frontiers in Immunology. 2022-July-04 2022;13doi:10.3389/fimmu.2022.907750
13. De Roover A, Escribano-Núñez A, Monteagudo S, Lories R. Fundamentals of osteoarthritis: Inflammatory mediators in osteoarthritis. Osteoarthritis Cartilage. Oct 2023;31(10):1303-1311. doi:10.1016/j.joca.2023.06.005
14. Yokose C, McCormick N, Choi HK. Dietary and Lifestyle-Centered Approach in Gout Care and Prevention. Current Rheumatology Reports. 2021/07/01 2021;23(7):51. doi:10.1007/s11926-021-01020-y
15. Backholer K, Pasupathi K, Wong E, Hodge A, Stevenson C, et al. The relationship between body mass index prior to old age and disability in old age. International Journal of Obesity, 2012; 36:1180.
16. Hall JE, do Carmo JM, da Silva AA, Wang Z, Hall ME. Obesity, kidney dysfunction and hypertension: mechanistic links. Nature Reviews Nephrology. 2019/06/01 2019;15(6):367-385. doi:10.1038/s41581-019-0145-4
17. Nawaz S, Chinnadurai R, Al-Chalabi S, et al. Obesity and chronic kidney disease: A current review. Obesity Science & Practice. 2023;9(2):61-74. doi:https://doi.org/10.1002/osp4.629
18. Zammit C, Liddicoat H, Moonsie I, and Makker H. Obesity and respiratory diseases. International journal of general medicine, 2010; 3:335-343.
19. Matu J, Griffiths A, Shannon OM, et al. The association between excess weight and COVID-19 outcomes: An umbrella review. Obesity Reviews. 2024;25(10):e13803. doi:https://doi.org/10.1111/obr.13803
20. Quek J, Chan KE, Wong ZY, et al. Global prevalence of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis in the overweight and obese population: a systematic review and meta-analysis. The Lancet Gastroenterology & Hepatology. 2023;8(1):20-30. doi:10.1016/S2468-1253(22)00317-X
21. Powell EE, Wong VW-S, Rinella M. Non-alcoholic fatty liver disease. The Lancet. 2021;397(10290):2212-2224. doi:10.1016/S0140-6736(20)32511-3
22. Renehan AG, Tyson M, Egger M, Heller RF, Zwahlen M. Body-mass index and incidence of cancer: a systematic review and meta-analysis of prospective observational studies. Lancet. Feb 16 2008;371(9612):569-78. doi:10.1016/s0140-6736(08)60269-x
23. Lauby-Secretan B, Scoccianti C, Loomis D, Grosse Y, Bianchini F, et al. Body Fatness and Cancer — Viewpoint of the IARC Working Group. New England Journal of Medicine, 2016; 375(8):794-798.
24. Alford S, Patel D, Perakakis N, and Mantzoros CS. Obesity as a risk factor for Alzheimer's disease: weighing the evidence. Obesity Reviews, 2018; 19(2):269-280.
25. Baranowski BJ, Bott KN, and MacPherson REK. Evaluation of neuropathological effects of a high-fat high-sucrose diet in middle-aged male C57BL6/J mice. Physiological Reports, 2018; 6(11):e13729.
26. Selman A, Burns S, Reddy AP, Culberson J, Reddy PH. The Role of Obesity and Diabetes in Dementia. Int J Mol Sci. Aug 17 2022;23(16)doi:10.3390/ijms23169267
27. Tanamas S, Magliano D, Lynch B, Sethi P, Willenberg L, et al. AusDiab 2012 - The Australian Diabetes, Obesity and Lifestyle Study. Melbourne, Australia: Baker IDI Heart and Diabetes Institute, 2013.
28. Abdullah A, Wolfe R, Stoelwinder JU, de Courten M, Stevenson C, et al. The number of years lived with obesity and the risk of all-cause and cause-specific mortality. International Journal of Epidemiology, 2011; 40(4):985-996.
29. GBD Obesity Collaborators, Afshin A, Forouzanfar MH, et al. Health Effects of Overweight and Obesity in 195 Countries over 25 Years. N Engl J Med. Jul 6 2017;377(1):13-27. doi:10.1056/NEJMoa1614362
30. Global BMI Mortality Collaboration. Body-mass index and all-cause mortality: individual-participant-data meta-analysis of 239 prospective studies in four continents. Lancet, 2016; 388(10046):776-786.