Evidence presented in numerous medical studies shows that obesity is likely to increases the risk of developing 10 of the most common cancers. A new study of more than 400,000 adults in the United Kingdom, being presented at the European Association for the Study of Obesity (EASO) 28th European Congress on Obesity, held May 10 – 13, 2021, suggests that this is true regardless of how obesity it is measured.[1]

The authors of the study say that central fatness (larger waist and hips) and general obesity (body mass index or BMI and body fat percentage) are associated with similar estimates of cancer risk.

Their estimates suggest a substantial proportion of common cancers could be prevented by reducing obesity, including 44% of endometrial and 39% of uterine cancers in women, and 22%, 18%, and 17% of kidney, stomach, and liver cancer in both men and women, respectively.[1]

The results suggest that BMI is an adequate measure of cancer risk from excess weight, and there is no advantage in using more complicated or expensive measures such as waist circumference or body fat percentage.

Being overweight or obese is linked to an elevated risk of some cancers and premature death. However, most of the evidence is based on BMI, and little is known about the association between cancer and other markers of adiposity (eg, central obesity and body fat).[1][2]

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Using data from the UK Biobank prospective cohort study, researchers from the University of Glasgow identified 437,393 adults (54% women; average age 56 years) who were cancer-free, to investigate the risk of developing and dying from 24 cancers according to six markers of obesity: BMI, body fat percentage, waist-to-hip ratio, waist-to-height ratio, and waist and hip circumferences.

The results were adjusted for age, sex, ethnicity, deprivation, education, smoking, alcohol consumption, intakes of fruit and vegetables, red and processed meat, oily fish, physical activity, and sedentary behaviors.

Additionally, women-related cancer was further adjusted for hormonal replacement, age at menarche, and age at first and last live birth. Prostate cancer was additionally adjusted for family history of prostate cancer, and melanoma was further adjusted for sun exposure. After an average of 9 years of follow-up, there were 47,882 cases of cancer and 11,265 cancer deaths.

Obesity measures
The researchers found that all six obesity measures were positively and similarly associated with a higher risk for 10 cancers. For example, each 4.2 kg/m2 (men) and 5.1 kg/m2 (women) increase in BMI above 25 kg/m2 (defined as being overweight) was linked with higher risk of cancers of the stomach (35% increase), gallbladder (33%), liver (27%), kidney (26%), pancreas (12%), bladder (9%), colorectal (10%), endometrial (73%), uterine (68%), postmenopausal breast (8%), and overall (3%) cancer.

Based on the results, the researchers estimate that if these associations were causal, being overweight or obese could be responsible for around 40% of endometrial and uterine cancers and 29% of gallbladder cancers; and could account for 64%, 46%, and 40% of deaths from these cancers respectively

“We observed a linear association – the more severe obesity is, the higher the risk of developing and dying from these cancers, except for postmenopausal breast cancer”, said Carlos Celis-Morales, Ph.D., from the University of Glasgow, United Kingdom, who led the research.

“But there was a lot of variation in the effects of obesity on different cancers. This tells us that obesity must affect cancer risk through a different number of processes, depending on the cancer type,” Celis-Morales added

Being an observational study, the results do not establish cause, and the researchers say they cannot rule out the possibility that other unmeasured factors known as residual confounding, may have influenced the results. They also note that the study is not a representative sample of the UK adult population, so the results might not be generalizable to the general population.

Reference
[1] Parrea-Soto S, et al. Six adiposity-related markers associations with incidence from 24 cancers – Findings from the UK Biobank prospective cohort study. Abstract TS02.03 Presented at: European Association for the Study of Obesity (EASO) 28th European Congress on Obesity, held May 10 – 13, 2021.
[2] Parra-Soto S, Cowley ES, Rezende LFM, Ferreccio C, Mathers JC, Pell JP, Ho FK, Celis-Morales C. Associations of six adiposity-related markers with incidence and mortality from 24 cancers-findings from the UK Biobank prospective cohort study. BMC Med. 2021 Jan 11;19(1):7. doi: 10.1186/s12916-020-01848-8. PMID: 33423670; PMCID: PMC7798245. [Read Article]

Featured image: A tailor’s measuring tape on a dinner fork. Photo courtesy: ©2016 – 2021 Fotolia/Adobe. Used with permission.

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