Published: Wed, February 06, 2019
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Obesity-linked cancers on the rise in young adults

Obesity-linked cancers on the rise in young adults

It's not possible to definitively attribute the recent cancer increases to obesity - but the new report notes that the upticks in cancer for young people coincided with a doubling in rates of childhood and adolescent obesity between 1980 and 2014, making weight a likely contributor.

But for six of the 12 obesity-related cancers - colorectal, endometrial, gallbladder, kidney, pancreas and multiple myeloma there was a steady increase in incidence over the years, with larger increases in younger adults.

Most of these cancers have traditionally shown up in patients later in life, usually in their 60s and 70s.

The study suggests that the sharpest increase in obesity-related cancer incidence is in adults aged 25 to 49.

Take pancreatic cancer for example, typically diagnosed in people over age 65.

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).

In contrast, rates of cancers that are linked to infection or smoking (nonobesity related) declined or were stable in all but 2 of 18 types of cancers. "The steepest increases were in the youngest age group, those aged 25 to 34 years".

While the United States has the highest obesity levels in the world, the UK's levels have risen by 92 per cent since 1991, compared with a rise of 65 per cent in the U.S., making it the sixth fattest nation in the developed world.

However, Chang warns against overgeneralizing on the basis of an epidemiological study. But, Dr. Schwartz says, other studies show "how obesity contributes to a chronic state of inflammation in our bodies, and that chronic state is known to promote carcinogenesis in animal models". "We know there are many factors that are associated with both obesity and cancer, such as lack of exercise and poor diet". This could reflect the fact that some types of breast cancer are on the rise while others in decline.

Globally, obesity has reached "epidemic proportions", says the World Health Organization, which estimates that more than 1 billion adults are overweight, with at least 300 million of them considered clinically obese. Research in the United Kingdom shows at least seven in 10 people born between the early 1980s and mid-1990s will likely be overweight or obese by their mid-30s and 40s. People in the 40 to 44 age bracket only experienced a 0.72 percent increase, according to the study.

A study in the New England Journal of Medicine a year ago found nearly 60% of the nation's children and teens will be obese by the age of 35 if the trend continues, with around half of the projected weight gain occurring during childhood.

One in 20 cases of cancer in the United Kingdom are linked to excess weight. They also release hormone-like fatty acids and proteins that affect metabolism, body weight and reproductive functions. Others studies show the location of fat - such as fat in the abdomen - may impact cancer risk.

Obesity is now one of the most preventable causes of cancer in both the U.S. and the United Kingdom - around 1 in 12 cases in the USA are caused by excess weight and more than 1 in 20 in the UK. Not everyone who gets these cancers will be overweight and everyone who is obese will not necessarily get these cancers. The cancer-obesity issue "is a really important topic because we've had an obesity crisis now for a number of decades", said John Jakicic, a professor and director of the Healthy Lifestyle Institute at the University of Pittsburgh in Pennsylvania. That, he said, should be a wake-up call for doctors, policy makers and the public, especially when it comes to childhood obesity.

Chang agreed that urgent action is needed.

More than half of 20 to 49-year-olds eat for too little fruits, vegetables and whole grains, and too much salt, fast food and sugary drinks, she said.

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