The meta-analysis describes how obesity has shifted certain cancers to younger age groups, and intensified cellular mechanisms promoting the diseases.
Cancer typically associated with older adults over 50 are now reported with increasing frequency in young adults, said the researchers at Case Western Reserve University in the US.
In 2016, nearly one in 10 new breast cancer cases, and one in four new thyroid cancer cases were in young people aged 20-44, according to the study published in the journal Obesity.
The new research integrates animal studies, clinical trials, and public health data to help explain rising cancer rates among young adults. It describes how the childhood obesity “pandemic” promotes cancer. It also offers approaches to better track – and hopefully avert – this public health crisis.
Young people with body mass indexes (BMIs) over 30 are more likely to experience aggressive malignancies, said Nathan A Berger from Case Western Reserve University.
According to his research, childhood obesity may have lasting effects that could lead to cancer early and late in life. Obesity can permanently alter a young person’s likelihood of developing cancer. Even after losing weight, cancer risk remains. “If you are obese, you are at a higher risk of cancer. If you lose weight, it improves the prognosis and may lower your risk, but it never goes away completely,” Berger said.
Obesity causes changes to a person’s DNA that can add up over time. These changes include genetic flags and markers – epigenetic modifications – that increase cancer risk and may remain long after weight loss. Data from clinical trials and animal obesity studies further link excess weight to cancer.
The study shows that obesity accelerates cancer progression in several ways. It over-activates the immune system to produce harmful byproducts like peroxide and oxygen radicals that mutate DNA. Obesity also alters a person’s metabolism, causing growth factor and hormone imbalances that help cancer cells thrive.
In the gut, obesity changes intestine microbiota such that tumour – promoting species dominate. Acid reflux in obese individuals damages their swallowing tubes and heightens risk of esophageal cancer. Berger’s research confirms that obesity promotes cancer by multiple simultaneous pathways. “Even if one pathway is successfully blocked, obesity-induced cancer takes another path,” he said.