Obesity has shifted certain cancers into younger age groups, say researchers at Case Western Reserve University School of Medicine.
The researchers investigated more than 100 studies to compile evidence showing how obesity increases cancer risk.
Currently, cancer is usually linked to adults over the age of 50, but the meta-analysis found that certain cancers are occurring more frequently in younger people, spurred by obesity.
In 2016, nearly 1 in 10 new breast cancer cases, and 1 in 4 new thyroid cancer cases were in young people aged 20-44.
The new review combines animal studies, clinical trials, and public health data to help explain why cancer rates are rising among young adults. It describes how the childhood obesity “pandemic” promotes cancer, and discusses how to better track, and perhaps avert, this public health crisis.
Childhood obesity can influence the risk of cancer throughout life, said study author Dr. Nathan A. Berger, and young people with body mass indexes (BMIs) over 30 are more likely to have aggressive malignancies.
The increased risk remains even after losing weight.
“If you are obese, you are at a higher risk of cancer,” said Berger. “If you lose weight, it improves the prognosis and may lower your risk, but it never goes away completely.”
The reason? Obesity makes changes in DNA that can add up over time. These changes include genetic flags and markers that increase cancer risk and can remain long after weight loss.
Obesity stimulates the immune system to produce harmful byproducts like peroxide and oxygen radicals that mutate DNA. In addition, obesity alters metabolism, causing growth factor and hormone imbalances that help cancer cells thrive.
In the gut, obesity changes intestine microbiota to the point where those that promote tumors predominate. Berger’s research confirms obesity promotes cancer by multiple simultaneous pathways. “Even if one pathway is successfully blocked, obesity-induced cancer takes another path,” he says.
“The most effective way to curtail development of this problem is to prevent the expansion of the obesity pandemic in both children and adults,” he said.
The study was published in the journal Obesity.
A report from the Centers for Disease Control and Prevention released in late 2017 found that 40 percent of all cancers in the United Stares were linked to obesity. There were 13 cancers found to be associated with obesity:
• postmenopausal breast
• multiple myeloma
The report, which was published in the CDC’s Morbidity and Mortality Weekly Report, stated that although the rate of new cancers has decreased in the past two decades, there has been an increase in cancers related to being overweight or obese.
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