Is there a link between obesity and cancer risk?

Obesity:

Obesity, or adiposity, is a recognized chronic disease. According to the definition of the German Obesity Society, it is an accumulation of fatty tissue in the human body that exceeds normal levels and belongs to the group of hormonal, nutritional and metabolic diseases. Obesity can lead to insulin resistance, hypertension or dyslipidemia. Although science knows that obesity is also an important factor in mortality from carcinoma, this knowledge is limited by the gap in knowledge from its relation to its impact on public health.

Previous studies have shown correlations between obesity and increased risk of carcinoma of the endometrium (i.e., inner lining of the uterus), kidney, gallbladder, breast (in postmenopausal women), and colon. As early as 1998, adenocarcinoma of the esophagus was associated with obesity. Analyses of cancers of the pancreas, prostate, liver, cervix, and ovary are less frequent due to the limited number of studies or are inconsistent or biased in their analysis due to smoking-related cancers. To better characterize the influence of severe obesity for increased cancer risk, a 2003 study published in the New England Journal of Medicine examined this association.

16-year study:

This involved prospectively following more than 900,000 U.S. adults (404,576 men and 495,477 women) over a 16-year period from 1982 to 1998. All participants were cancer-free at baseline - 57,145 cancer-related deaths were recorded over the 16 years. The researchers examined the relationship between the 1982 BMI value (i.e., body mass index) and cancer risk for all cancers and for cancers at specific locations on the human body, while also accounting for other risk factors. Using risk estimates from studies at the time and estimates of the prevalence of obesity in the U.S. adult population, the proportion of all cancer deaths that were attributable to obesity was calculated.

Study associated incidence cases:

Male cohort participants with the greatest BMI of at least 40 (i.e., weight in kilograms divided by the square of height in meters) experienced 52% higher mortality rates for all types of cancer than men and women with "normal" BMI levels. Severely overweight women even had a 62% higher risk of cancer than the comparison group.

In both sexes, BMI levels were associated with increased death rates from cancer of the esophagus, colon, liver, gallbladder, pancreas, and kidney. In men, increasing risk was associated with higher BMI levels for death from stomach and prostate cancers, and in women, from breast, uterine, cervical, and ovarian cancers. According to the study, it is estimated that current patterns of overweight and obesity in America may be responsible for about 14% of all cancer deaths in men and 20% in women. It should be noted that the data was collected between 1982 and 1998. According to statistics, in 1990, about 23% of the American population was overweight - by 2015, that number had risen to 38.5%.

An old pattern:

Further studies index an increase in cancer incidence for certain types of carcinoma, even in younger adults. To that end, a 2020 study publishedin the journal Cancerexamined incidence rates for 28 cancer types in Canada. It assessed Canadian incidence data for 20- to 84-year-olds from the Cancer Incidence in Five Continents Plus database and categorized groups by age and year of birth from 1983 to 2012. The research found that people born in 1988 had twice the risk of colon cancer and five times the risk of rectal cancer than people born in 1943. In contrast, the risk of lung cancer was about 60% lower in later generations than before.

Conclusion:

Highly elevated body weight may be associated with increased mortality rates for certain cancers and cancers of specific body sites, according to studies. Among young adults, the incidence of some obesity-associated cancers is increasing, while cancers associated with infections or smoking are decreasing. Despite the need for further studies - to validate current statistics and better understand the cause of early-onset cancers - young adults should promote sustainable health behaviours, according to the findings.