PARIS: A sharp increase in obesity-linked cancers amongst young adults in the United States could foreshadow a reversal in the overall decline in cancer mortality, researchers warned on Monday.

In a sweeping study covering two-thirds of the US population, they showed that half a dozen cancers for which obesity is a known risk factor became more frequent from 1995 to 2015 amongst women and men under 50.

The younger the age bracket, the more quickly these cancers gained ground, they reported in The Lancet, the medical journal.

During the period examined, the incidence of pancreatic cancer, for example, increased by about one per cent per year for adults aged 45 to 49. Amongst 30 to 34-year-olds, the average annual increase was more than twice that. Amongst 25 to 29-year-olds, the rate jumped by 4.4 per cent per year.

Comparing five-year age brackets from 25 to 80, the annual hike was similarly highest amongst the 25 to 29 cohort for four other obesity-linked cancers: kidney (6.23 per cent), gallbladder (3.71 per cent), uterine (3.35 per cent), and colon (2.41 per cent).

“Our findings expose a recent change that could serve as a warning of an increased burden of obesity-related cancers to come in older adults,” said co-author Ahmedin Jemal of the American Cancer Society, USA.

Obesity has more than doubled in the United States over the last four decades. It has also risen sharply in other rich nations and, more recently, the developing world. Today, some two billion people are overweight or obese.

With few exceptions, cancer has been seen as a disease of ageing. Indeed, the researchers note that the number of new cancer cases reported remains much higher in older age brackets, even if the rate of increase is now fastest amongst young adults.

Overall, the number of people in the United States who succumb to cancer has declined.

“But in the future, obesity could reverse that progress,” co-author Jemal cautioned. “Obesity is now one of the most preventable causes of cancer in the US and UK — around one in 12 cases in the US is caused by excess weight, and more than 1 in 20 in the UK.”

“This study should be a wake-up call to all Americans, young and old alike,” the American Society of Clinical Oncology said in a statement. “Obesity is set to overtake tobacco as the leading cause of preventable cancer-related death, and there is an alarming lack of awareness amongst the American public of the link between obesity and cancer.”

The authors called for more aggressive screening for obesity by front-line doctors, and called on them to warn patients about the cancer risk of being seriously overweight.

Published in Dawn, February 5th, 2019