Obesity-related cancer is rising among both young and older adults, according to global study

A new global study has found that cancer cases are increasing among younger populations across much of the world – with much of the increase linked to obesity.

The rise is not limited to people under 50, with older generations seeing similar upward trends.

The research, published this week in the Annals of Internal Medicine, examined cancer data from 42 countries across five continents between 2003 and 2017.

Scientists analysed 13 types of cancer previously reported to be rising in younger adults.

The findings confirm that several cancers are indeed becoming more common among adults aged 20 to 49. These include thyroid, breast, colorectal, kidney, endometrial cancer, and leukemia – all of which saw rising rates in more than three-quarters of the countries studied.

Thyroid cancer showed the steepest increases, with a median average annual percentage change of 3.57 per cent, followed by kidney (2.21 per cent) and endometrial cancers (1.66 per cent).

Colorectal cancer, one of the most widely discussed early-onset cancers, rose by 1.45 per cent per year on average among younger adults. While rates rose for both younger and older adults for most cancers, colorectal cancer was the exception.

In nearly 70 per cent of countries, new diagnoses grew faster in younger adults than in older populations.

The study noted that the upward trend across multiple cancer types suggests there could be shared underlying factors, including rising obesity rates, changes in diet, and antibiotic use.

Older adults still bearing the highest burden

While the findings underscore the growing concern about early-onset cancers, the researchers cautioned against focusing prevention efforts solely on younger adults. Despite rapid increases in some cancers among people under 50, the total number of cases remains much higher in older populations.

For example, in the United States, about 50,000 women under the age of 50 were diagnosed with breast cancer in 2022 – compared with more than 210,000 among those over 50.

The researchers called for more studies into the causes of the upticks.

The latest findings “can help guide future research priorities and clinical priorities, such as the need for special treatment strategies and supportive care needs for younger patients with cancer," the report concluded.

Are early-onset cancers really rising – or are doctors just finding more cases?

A study released last month suggests that much of the increase in early-onset cancers may be due to overdiagnosis, rather than a true rise in the disease.

Published in JAMA Internal Medicine, researchers looked at the eight cancers with the fastest-rising incidence – thyroid, anus, kidney, small intestine, colorectal, endometrial, pancreas, and myeloma – among adults under 50.

They found that while diagnoses of these cancers have roughly doubled since 1992, mortality rates have remained remarkably stable. This suggests that the rise in reported cases largely reflects increased detection and overdiagnosis, rather than a true surge in life-threatening disease.

The authors of the study cautioned that framing early-onset cancer as an epidemic risks exaggerating the problem and may have unintended consequences.

Unnecessary diagnoses, for example, can impose significant emotional, physical, and financial burdens on patients, subjecting otherwise healthy young adults to invasive treatments and long-term monitoring that does not actually improve their health.