It is a pattern that has worried and baffled experts in equal measure: why are so many cancers, once thought of as diseases of old age, striking younger people?

Among the chief causes for concern is colorectal, or bowel cancer, with cases rising at a rapid pace among younger adults. 

But it is far from the only disease driving alarm. 

Rates of ovarian, pancreatic, kidney, thyroid and several other cancers are also climbing in under 50s.

Now, a major new study, published in the world-renowned British Medical Journal, suggests a cluster of everyday lifestyle habits may be driving the trend.

Researchers analyzed rates of 11 cancers increasing in younger adults in England to investigate why more people are being diagnosed earlier in life. 

They identified seven behavioral risk factors linked to these diseases: smoking, excess weight, alcohol, physical inactivity, red meat, processed meat and low fiber intake.

But while all seven are known to raise cancer risk, the researchers found obesity stood out as the only one clearly worsening over time – leading them to ask what else could be driving the phenomenon?

Other major risk factors were either improving, with fewer young people smoking and heavy drinking rates falling, or remaining broadly stable, such as fiber intake and physical inactivity.

The authors from The Institute of Cancer Research in London and Imperial College London also found that, unlike many other cancers, colorectal and ovarian cancer were rising in younger adults but not older generations – suggesting something different may be affecting younger people.

Their conclusion: Lifestyle still matters enormously but the rise in young cancers is likely being driven by a mix of obesity, modern environmental exposures, changes to the gut microbiome and other emerging factors that need urgent investigation.

To find out more, the Daily Mail spoke to Dr Cedrek McFadden, a board-certified colorectal surgeon in Greenville, South Carolina, who specializes in treating colorectal cancer. 

He explained what people can do today to help protect themselves against the deadly disease. 

Why are young people getting colon cancer?

Colon cancer – often grouped with rectal cancer as bowel or colorectal cancer – has long been considered a disease of older age.

However, as far back as the mid-2000s, experts recorded an increase in what they then called 'early-onset' disease.

Then came a landmark 2017 study by the American Cancer Society which suggested these cases weren't an anomaly but a worrying epidemiological shift.

It found those born in 1990 facing double the risk of colon cancer and quadruple the risk of rectal cancer compared to those born around 1950. 

On ground level, Dr McFadden said the trend has been impossible to ignore.

'It concerns me – definitely,' he said. 'Colon cancer really stands out because it is rising in young patients.

'When you compare it with what is happening in older adults, this is the cancer that really seems to be shifting toward the younger generation.'

He said the findings of the new study challenge the idea that the surge can be explained simply by poor lifestyle choices.

'This paper shows it is likely much more complicated than that,' he said. 'In our own practice, we see patients as young as their 20s. We are seeing more people in their 30s and 40s than we used to – and that gets your attention.'

What concerns him most, he said, is that many younger patients do not fit the traditional high-risk profile doctors have long been taught to look for.

'They are not always the patients with a family history of colorectal cancer,' he said.

'They may not have obesity, a personal history of polyps, Crohn's disease, ulcerative colitis or the classic diet low in fiber and high in processed food. Those factors still matter, but we are seeing more patients who do not tick those boxes. That is what makes this feel different from what we have traditionally seen.'

Symptoms can include blood in the stool, persistent changes in bowel habits, unexplained abdominal pain, bloating, fatigue, weight loss or anemia.

The new study examined English cancer registry data from 2001 to 2019 and found colorectal cancer was one of the clearest examples of a disease increasing in younger adults while remaining broadly stable in older people.

It adds to a growing body of evidence on the trend.

Just this month, another major US study found rectal cancer deaths are rising particularly fast in younger adults, with researchers warning cases in under-50s have become an increasing global concern.

Using more than 20 years of Centers for Disease Control and Prevention (CDC) records, researchers in New York found fatalities linked to the disease in people under 45 are rising up to three times faster than colon cancer in the same age groups.

The emerging picture suggests there may be what scientists call generational exposures – factors affecting younger people differently from their parents and grandparents.

The seven habits linked to colon cancer risk...

Of all the cancers studied, bowel cancer was the only one linked to every risk factor examined. These were: 

1. Excess weight

Being overweight or obese is associated with chronic inflammation, raised insulin, hormonal disruption and metabolic changes that can help tumors grow.

The study found obesity has risen steadily since 1995 and was the only major behavioral risk factor clearly worsening over time.

2. Smoking

Tobacco smoke contains carcinogens that damage DNA throughout the body, including the digestive tract.

Smoking rates have fallen sharply, especially in younger adults. 

3. Alcohol

Alcohol is broken down into acetaldehyde, a toxic compound that can damage cells, interfere with DNA function and trigger mutations than lead to cancer.

Younger adult drinking trends were described in the study as 'decreasing' or 'stable' - with the exception of light drinking in younger men, which had increased. 

4. Physical inactivity

Exercise is described by experts as a 'powerful' drug-free way to regulate the body's metabolic and digestive health. It improves sensitivity to the hormone insulin, which helps cells burn sugar and fuel and dampens inflammation.

It also aids gut motility, helping move waste through the digestive system. Frequent bowel movements stimulated by exercise reduce the amount of time the colon is exposed to potential carcinogens in waste.

Inactivity was generally stable or improving rather than worsening, the study found.

5. Red meat

High intakes of red meat have been linked to bowel cancer, particularly when eaten frequently or cooked until heavily charred.

The study, however, found there had been large reductions in consumption between 2008 and 2018.

Among men, average intake fell from 38g a day to 17g a day – the equivalent of dropping from around 266g a week, roughly one medium steak plus a burger, to about 119g a week, or one small steak.

Among women, intake dropped from 22g a day to 10g a day – falling from around 154g a week, about one burger and a few slices of roast beef, to just 70g a week, roughly a single small burger.

6. Processed meat

Bacon, sausages and ham are classed as carcinogenic due to preservatives and compounds formed during processing.

Intake also declined.

7. Low fiber intake

Fiber supports healthy bowel movements and beneficial gut bacteria.

Although fiber intake remained too low for many people – the study suggested that 90 per cent of adults were deficient, defined as not hitting the 30g-per-day target – this was broadly stable or improving slightly. 

Dr McFadden said these risks are often deeply interconnected rather than acting in isolation.

'Obesity is one of the major risk factors, but it doesn't mean it is the only thing,' he said. 'There are certain behaviors that can increase the risk of obesity, like larger portions or processed foods. It's a compounded problem.'

He said excess body fat is 'not just stored energy' but biologically active tissue that can change the body in ways that may promote cancer growth.

'It creates a low level of inflammation in the body and, over time, this can damage cells and increase the risk of cancer,' he said. 'Obesity causes insulin levels to rise and affects other hormones that tell the body to grow. It also affects hormones like estrogen.'

On diet, he said red and processed meat can increase risk, particularly when eaten regularly.

'Processed meat – bacon, sausage – even a couple of slices of bacon a day can increase your risk,' he said. 'Red meat like beef or lamb, if you consume it on a daily basis, can increase the risk. It's a moderate risk – it's not the main driver.'

He noted that meat consumption has been falling while colorectal cancer has continued to rise.

'That tells us this alone isn't what we are seeing,' he said. 'These factors are part of the picture, but they do not totally explain the rise.'

... and the OTHER factors now in the frame 

The researchers estimated how many cancers could be linked to modifiable behaviors.

They found a substantial proportion of bowel cancers may be attributable to known risk factors – but obesity was the standout worsening trend.

When they separated obesity-related colorectal cancers from non-obesity-related cases, both were rising, though obesity-linked cases were increasing faster.

That suggests weight gain is playing an important role, but researchers also said it meant this factor alone cannot fully explain the young bowel cancer boom.

And because many of the other classic risk factors – such as smoking and heavy drinking – are actually falling, while others like fiber intake have stayed broadly similar, experts are now looking for other triggers.

Among the factors under growing scrutiny are ultra-processed foods – products such as ready meals, fizzy drinks, packaged snacks and fast food that are often high in additives, emulsifiers, salt and sugar. 

Some scientists believe these may disrupt metabolism, damage the delicate lining of the gut and alter the bacteria living there, potentially leading to cancer.  

Another theory centers on antibiotic exposure in childhood.

While these medicines can be lifesaving, frequent use may disturb the gut microbiome at a crucial stage of development, potentially causing long-term changes in digestion, immunity and inflammation.

Pollution is another suspect, including traffic fumes and airborne particles that can trigger chronic inflammation and expose the body to harmful chemicals.

Then there are 'forever chemicals', known as PFAS, which are used in non-stick pans, waterproof clothing, food packaging and some household products. 

As these material age, the shed microscopic particles that can linger in the environment and body for years, and some studies have linked them to hormone disruption and cancer risk.

The study also highlighted growing interest in gut bacteria that may produce toxins capable of damaging DNA in the bowel – a theory some scientists believe could help explain why younger generations appear to face greater risk.

Dr McFadden said one of the most striking ideas is that scientists may be looking too late in life for the roots of the problem.

'Early-life exposures really stand out to me,' he said. 'We may be looking too late.

'What happens in childhood – what we are eating, chemicals we are exposed to, even early weight gain – could be shaping cancer risk years before someone is diagnosed.'

He compared it to heart disease, where damage often begins very early on in life, decades before symptoms appear.

'Once someone has a heart attack, their arterial disease has usually been developing for years,' he said. 

'I think there is a lot of truth in the idea that early-life exposures can shape cancer risk decades before diagnosis.'

Beyond bowel cancer: the ovarian clue and the wider rise

As with colorectal cancer, ovarian cancer rates were rising in younger women while falling in older women.

Rising rates in both younger and older patients were also seen in pancreatic, kidney, liver, thyroid, endometrial, gallbladder, breast and oral cancers, as well as multiple myeloma.

For several of these – including endometrial, kidney, pancreatic, thyroid and multiple myeloma – rates were increasing faster in younger adults than in older age groups.

Scientists suspect broader forces may be at work, including obesity, metabolic dysfunction, environmental chemicals, changing diets, later parenthood, disruption to the gut microbiome and increased detection through scans and testing.

What you can do now to protect yourself

While the mystery is still unfolding, doctors stress people are not powerless.

Dr McFadden said the first step is recognising that bowel cancer can happen in younger adults – and not dismissing warning signs.

'Often, the diagnosis we miss is the one we do not consider,' he said.

He urged people to seek medical help for symptoms such as rectal bleeding, changes in bowel habits, unexplained weight loss, fatigue, persistent abdominal pain or anemia.

'Pay attention to the signs and symptoms,' he said. 'If warning lights are going off, it needs to be checked. It could be colorectal cancer.'

He said screening remains one of the most powerful tools because it can detect polyps and pre-cancerous growths before they turn dangerous.

'We currently recommend screening from 45,' he said. 'But regardless of age, if you have symptoms you still need to be tested. 

'Even if you are 25 with no family history, if you have symptoms you still need to be checked and may need a colonoscopy.'

Alongside vigilance and screening, experts say the most evidence-backed steps remain maintaining a healthy weight, exercising regularly, avoiding smoking, limiting alcohol, eating more fiber-rich foods such as beans, vegetables and wholegrains, reducing processed meat and knowing your family history.

Dr McFadden said some risks cannot be changed, such as age or genetics, but many can.

'You can control tobacco use, smoking and obesity,' he said. 

'You can control how much ultra-processed food and processed meat you eat, and how much exercise you take on a daily basis. 

'You can also make sure you get the right screening and pay attention to symptoms.'