As more and more young American adults struggle with excess weight, they pay an even higher price because cancers related to obesity increase in this age group.

Obesity has already been linked to rising rates of Type 2 diabetes, cardiac disease and knee replacements. New research suggests that cancer can be added to this list and that the rate of obesity-related cancers will continue to increase in the 25 to 49 age group, researchers said.

"The fact that the increases mainly concern cancers related to obesity is due to the obesity epidemicand we expected the incidence to increase as this young population ages, "said lead researcher Dr. Ahmedin Jemal, who is vice-president of science for surveillance and service research. at the American Cancer Society.

In fact, these cancers increase more rapidly in younger adults than older people, which could block or reverse years of progress in reducing the number of cancer deaths, said the study's authors.

In an attempt to curb the rising trend of cancers among obese, Jemal believes that primary care physicians must screen for obesity in all their patients. Family physicians should also advise patients to lose weight.

Although screening for most of these cancers is not available or helpful for younger patients, colon cancer is an exception, said Jemal.

Last year, the American Cancer Society lowered from 50 to 45 years the age of onset of colon cancer screening among people at medium risk.

Colorectal cancer screening should start at age 45, according to new guidelines

Communities must also take steps to promote healthy lifestyles, suggested Jemal. These may include the mandatory prescription of the number of calories on prepared foods and restaurant meals, as well as the limitation of sales of sugary drinks.

In addition, communities can offer people more opportunities to exercise by creating bike paths and hiking trails.

According to the study, increases in the incidence of cancer were particularly severe in six of the 12 cancers related to obesity.

These include cancers of the colon, uterus, gallbladder, kidneys and pancreas, as well as multiple myeloma, a cancer of the bone marrow.

The Jemal team examined 18 other types of cancer, but only two showed a similar increase, while eight smoking-related cancers declined and the rest remained stable.

For the study, researchers analyzed data from 25 state cancer registries covering 67% of the US population. The researchers examined 30 of the most common types of cancer, including 12 obesity-related cancers diagnosed between 1995 and 2014.

The incidence of multiple myeloma and cancers of the colon, uterus, gallbladder, kidneys, pancreas and thyroid increased in young adults, the results showed.

For example, the average annual rate for pancreatic cancer was about 1% among 40 to 84 year olds, 1.3% among 35 to 39 year olds, nearly 3% among 30 to 34 year olds and 4% among 25 to 29 year olds.

Of the six types of cancers related to obesity, the annual increase ranged from less than 1% for uterine cancer to 3% for kidney cancer in the 45 to 49 age group and from 1% for multiple myeloma up to 6% for kidney cancer in those aged 25 to 29 years.

However, although rates are rising faster among young adults, the overall rate is lower than that of older adults, according to the report.

The rate of breast cancer, also related to obesity, has not changed in young women. Researchers have suggested that some types of breast cancer are increasing while others are declining. Other factors, such as changes in age from screening and age to first pregnancy and the number of children, could also play a role.

These findings seem to reflect the epidemic of obesity that has plagued 40 years, said the authors of the study. In the United States, the obesity rate more than doubled between 1984 and 2014.

Obesity is one of the most preventable causes of cancer. In the United States, about one out of 12 cases of cancer is due to being overweight, the researchers noted.

Obesity is an emerging risk factor causing a significant number of cancers, said Elizabeth Platz, a cancer prevention specialist at the Johns Hopkins Bloomberg School of Public Health in Baltimore. .

Platz thinks that the problem is so vast that targeting individuals will not reduce the epidemic of obesity.

She also does not think that a magic pill to lose weight, if there was one, is a good approach. By taking this route, many problems and side effects could appear, said Platz.

"The changes must happen at the level of society," she suggested. "What this study shows is that they are generations of people."

A cultural change – getting people to eat less and exercise more – is needed, she said. "We need the political will," Platz said.

The report was published online on 4 February in The Lancet Public Health.