Abstract
BackgroundObesity and metabolic syndrome (MetS) appear in clusters and are both associated with an increased risk of cancer. However, it remains unknown whether obesity status with or without MetS increases the risk of site-specific cancers.MethodsWe used data derived from 390,575 individuals (37–73 years old) from the UK Biobank who were enrolled from 2006–2016 with a median of 7.8 years of follow-up. Obesity was defined by BMI ≥ 30 kg/m2 and MetS was defined by the criteria of the Adult Treatment Panel-III (ATP-III). Cox proportional hazards models were used to investigate the associations of BMI and MetS with 22 cancers.ResultsMetabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO) phenotypes represented 6.7% and 17.9% of the total analytic samples and 27.1% and 72.9% of the included subpopulation with obesity, respectively. Obesity was independently associated with higher risks of 10 of 22 cancers. Stratified by metabolic status, the MUO phenotype was consistently associated with 10 obesity-related cancers. In contrast, the MHO phenotype was only associated with increased risks of five cancers: endometrium, oesophagus, kidney, pancreas and postmenopausal breast cancers.ConclusionEven in metabolically healthy individuals, obesity was associated with increased risks of five cancers, whereas we did not find that these individuals were associated with increased risks of several other obesity-related cancers.
Highlights
Obesity and metabolic syndrome (MetS) appear in clusters and are both associated with an increased risk of cancer
Obesity was defined as a body mass index (BMI) ≥ 30 kg/m2, overweight was defined as 25 ≤ BMI < 30 kg/m2, and normal weight was defined as 18.5 ≤ BMI < 25 kg/m2
In the combined analysis of BMI and MetS, participants were divided into six phenotypes: metabolically healthy normal weight (MH-NW), metabolically unhealthy normal weight (MUNW), metabolically healthy overweight (MH-OW), metabolically unhealthy overweight (MU-OW), Metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO)
Summary
Obesity and metabolic syndrome (MetS) appear in clusters and are both associated with an increased risk of cancer. Some individuals with obesity have few or no elevated metabolic risk factors (e.g. blood pressure, triglyceridemic, hyperglycaemia and low HDL cholesterol),[7] suggesting that there may be a subset of individuals with obesity, who have metabolically healthy obesity (MHO).[8] The proportion of those with MHO among the entire population with obesity ranges from 10–40%, depending on the population under study and the criteria used to define MetS.[9] A previous study in the UK showed that 9.3% of participants were affected by obesity and that 42.5% of them were classified as the MHO phenotype.[10] The classification of obesity into MUO and MHO phenotypes has been increasingly recognised and used by clinicians and public health practitioners in their clinical and public health practices, e.g. in determining clinical treatments for obesity.[11]
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