When it comes to cancer, there are many things beyond our control – from the genes we inherit to the simple bad luck of developing the disease.
But scientists have found that a surprisingly large proportion of cases are linked to factors we can change.
In fact, a major study by the American Cancer Society (ACS) estimated that four in ten cancer diagnoses in the US – more than 713,000 cases in 2019 – were linked to potentially preventable risk factors.
The same was true of an even greater proportion of cancer deaths – 44 percent, or more than 262,000 deaths that year.
The researchers examined 30 types of cancer, looking at the impact of smoking, excess weight, alcohol, diet and physical inactivity, among other factors.
Smoking was by far the biggest contributor, accounting for almost one in five cases. Excess weight was responsible for a further 8 percent, while alcohol accounted for 5 percent.
And research suggests that making healthier choices could substantially reduce the chances of developing the disease.
A separate analysis, published in 2025, examined 28 long-term studies investigating the benefits of following established cancer prevention guidelines, including maintaining a healthy weight, exercising regularly and eating a balanced diet.
Eating more vegetables is one of the simplest ways to improve your diet and reduce cancer risk
It found that people who followed the recommendations most closely had a 14 percent lower overall risk of cancer than those who followed them least.
For some cancers, the difference was even greater: 35 percent for uterine cancer, 31 percent for colorectal cancer and 38 percent for kidney cancer.
The findings come amid growing concern about the rising rates of certain cancers among Americans under 50.
A 2025 National Cancer Institute study identified increasing rates of 14 cancer types in at least one younger age group, including breast, colorectal, kidney and uterine cancers.
Scientists are still struggling to explain what’s driving these trends, with obesity, diet and environmental exposures among the possible causes being investigated.
But while the reasons remain uncertain, experts say there is already compelling evidence that changing certain everyday habits can help reduce cancer risk.
‘Until we know what’s exactly driving these early-onset cancers, the best thing we can do is focus on the risk factors we know we can change,’ said Dr Karen Knudsen, former CEO of the ACS.
So which changes are worth it, and how much difference could they really make? Here, leading cancer experts explain the moves that could help reduce your risk, and what the science says about how effective they are.
Ditch daily drinks and cut cancer by a quarter
Giving up two alcoholic drinks a day could reduce a woman’s estimated lifetime risk of developing an alcohol-related cancer by almost a quarter, according to US health officials.
Figures from the US Surgeon General suggest that 22 in every 100 women who drink twice daily will develop one of these cancers, compared with 17 in 100 who drink less than once a week – a relative difference of almost 23 percent.
For men, the corresponding figures are 13 and 10 in every 100. These are population estimates, however, not proof that quitting will reduce an individual’s risk by precisely that amount.
Alcohol is an established cause of at least seven cancers, including breast, bowel, liver, mouth and throat cancers.
When the body breaks down alcohol, it produces acetaldehyde, a toxin that can damage DNA. Drinking can also raise estrogen levels, which may help explain its link to breast cancer.
Even one drink a day is associated with a 7 to 10 percent higher risk of breast cancer in women, while two to three drinks increases the risk by around 20 percent.
So how much alcohol can you safely drink without increasing your cancer risk?
‘There is no level of alcohol consumption considered “safe” in relation to cancer,’ said Dr Fiona Malcomson, scientific adviser at the American Institute for Cancer Research (AICR).
A standard US drink means a 12-ounce beer, five-ounce glass of wine or 1.5-ounce shot of spirits.
Larger servings may contain two or more drinks.
And research suggests quitting can bring benefits, although these may take years to emerge.
Studies reviewed by the International Agency for Research on Cancer found that stopping drinking reduces the risk of certain cancers, particularly those of the mouth and esophagus.
‘Stopping drinking completely prevents further exposure to alcohol and acetaldehyde. However, this does not mean that cancer risk falls immediately,’ Malcomson said.
But cutting back is still worthwhile.
‘The AICR recommends avoiding alcohol to prevent cancer, but cancer risk is not all or nothing, and people who drink can still benefit from drinking less often and in smaller amounts,’ she added.
Lose a little weight to slash risk by 29 percent
Losing just 5 percent of your body weight could substantially reduce your risk of uterine cancer.
One study found that women with obesity who lost at least 5 percent of their body weight had a 29 percent lower risk of developing the disease than those whose weight remained stable.
For a woman weighing 200 pounds, that would mean shedding just 10.
Excess body fat is linked to at least 13 types of cancer, including uterine, colorectal, kidney and pancreatic – several of which are increasingly affecting younger adults.
Women with obesity face two to four times the risk of uterine cancer compared with women at a healthy weight, rising to around seven times for those with severe obesity.
But the dangers begin before someone becomes obese.
‘Being overweight can increase cancer risk, even before someone meets the definition of obesity,’ said Dr Timothy Rebbeck, professor of cancer prevention at Harvard.
Excess fat can raise levels of estrogen, insulin and other growth-promoting hormones, while triggering chronic inflammation – all of which may encourage cancer development.
And experts warn that where fat is stored may matter as much as how much someone weighs.
Visceral fat, which accumulates deep inside the abdomen around internal organs, is particularly associated with inflammation and insulin resistance.
Dr Edward Giovannucci, professor of nutrition and epidemiology at Harvard, said measuring your waistline can therefore be more revealing than simply calculating your body mass index.
‘That’s probably the single best measure of cancer risk because it gives an indication of how much fat is stored around the abdomen and internal organs,’ he said.
According to the Centers for Disease Control and Prevention, a waist measurement above 35 inches for women or 40 inches for men is associated with increased health risks.
And even substantial weight loss later in life may offer protection.
One major study found that adults with obesity who underwent weight-loss surgery had a 32 percent lower risk of developing obesity-related cancers and a 48 percent lower risk of dying from them, compared with those who did not undergo surgery.
There is also growing interest in whether weight-loss drugs such as Wegovy and Mounjaro could offer similar benefits.
‘The evidence for cancer prevention is currently promising but inconclusive,’ Malcomson said.
She stressed that the drugs are not currently recommended specifically to prevent cancer.
But experts say people who have been overweight for years should not assume it’s too late to benefit.
‘While the timeline varies by cancer type, some benefits of weight loss can become apparent within one to two years,’ Giovannucci said.
Five-minute habit linked to 20 percent fewer cases
You don’t need to spend hours in the gym to lower your cancer risk. Research suggests that just a few minutes of vigorous activity a day could make a substantial difference.
A 2023 study of more than 22,000 adults who did not exercise regularly found that those who accumulated around 4.5 minutes of vigorous activity a day had a 20 percent lower risk of developing cancer than those who did none.
And the activity didn’t have to involve a formal workout. Climbing stairs, walking briskly uphill or carrying heavy shopping could all count.
Crucially, exercise appears to offer protection against cancer even without weight loss.
‘It’s actually not enough to just have the right body weight for your size, you actually have to be physically active. Research shows that these are actually separable things,’ Knudsen said.
A major study of 1.44 million adults found that physical activity was associated with a lower risk of 13 cancers, including kidney, uterine, colon and breast, even after accounting for body weight.
Exercise is thought to help by regulating insulin and hormone levels, reducing inflammation and speeding the movement of food through the digestive system.
And less strenuous activity may also offer protection.
A 2025 study of more than 85,000 adults found that taking 7,000 steps a day was associated with an 11 percent lower cancer risk, rising to 16 percent for those taking 9,000 steps, compared with taking 5,000 steps.
Although these studies cannot prove that exercise directly prevents cancer, they suggest even small increases in movement may help.
Current cancer prevention guidelines recommend 150 to 300 minutes of moderate exercise, such as brisk walking or cycling, or 75 to 150 minutes of vigorous activity each week.
But experts stress that doing something is better than nothing.
‘You don’t need to be a marathon runner to get benefits,’ Rebbeck said.
And it’s never too late to start. A 2019 study found that adults who became more active later in life had a 16 percent lower risk of dying from cancer than those who remained inactive.
Knudsen said the secret is making exercise part of your daily routine.
‘When I’m home, my husband and I do what we call “coffee and a walk,”‘ she said. ‘We make our coffee and walk two miles through our neighborhood every morning.
‘Sometimes, it’s just these micro changes in the way you run your life that can make a big difference in cancer prevention.’
Even lifelong smokers can dramatically reduce their risk
It’s never too late to quit smoking, even for those who have smoked heavily for decades.
One major study found that long-term heavy smokers who gave up cigarettes had a 39 percent lower risk of lung cancer within five years, compared with those who continued smoking.
Smoking is the leading preventable cause of cancer in the US, responsible for an estimated 19 percent of diagnoses and almost 29 percent of cancer deaths.
Although most closely associated with lung cancer, tobacco smoke contains dozens of carcinogens that can enter the bloodstream and damage cells throughout the body, increasing the risk of at least 12 other cancers, including pancreatic, bladder and colorectal.
But research suggests that giving up cigarettes can produce substantial benefits surprisingly quickly.
According to the CDC, within five to ten years of quitting, the risk of cancers of the mouth and throat falls by around half compared with continuing to smoke. The additional risk of lung cancer falls by half after roughly 10 to 15 years.
And while quitting earlier offers the greatest protection, experts stress that older smokers can still benefit.
‘Any time you do things to reduce your cancer risk, there is benefit. If you stop smoking at age 60, you’re still going to reduce your cancer risk,’ Rebbeck said.
Tobacco smoke contains dozens of carcinogens that travel through the body
However, some risks persist. The same study found that even after 25 years, former heavy smokers still faced nearly four times the lung cancer risk of people who had never smoked.
The message, experts say, is that quitting as soon as possible offers the greatest protection, but it’s never too late to make a difference.
An extra 10g of fiber a day could protect against bowel cancer
One of the simplest ways to lower your cancer risk may be to eat more fiber.
A major analysis by the World Cancer Research Fund found that every additional 10g of fiber consumed daily was associated with a 10 percent lower risk of colorectal cancer.
That’s roughly the amount found in a cup of cooked black beans or raspberries, making it a relatively achievable change.
Fiber is thought to protect against cancer by helping food move through the digestive system, reducing the time potentially harmful substances spend in contact with the bowel lining.
It also feeds beneficial gut bacteria, which produce compounds that may help reduce inflammation and protect cells from damage.
Whole grains, beans, lentils, fruits and vegetables are among the best sources, and experts recommend eating a variety rather than relying on a single food.
But what you eat less of may also matter.
A large 2023 analysis involving more than 625,000 people found that those who consumed the most ultra-processed foods had a 13 percent higher risk of cancer overall than those who ate the least.
These foods are often high in calories, added sugars and unhealthy fats, while being low in fiber. Regular consumption can contribute to weight gain and obesity, both established cancer risk factors.
However, experts caution that not all ultra-processed foods are equally unhealthy.
‘Rather than looking to see if something is labeled as “ultra-processed,” I would focus on the calories and nutrients, especially where the calories are coming from,’ Giovannucci said.
‘Not all ultra-processed foods are the same. A doughnut and balsamic vinegar are both, technically, ultra-processed, but I would avoid eating the 700 empty calorie doughnut much more,’ he said.
And people shouldn’t feel they have to overhaul their diet overnight.
‘There’s the ideal, and then there’s reality,’ Knudsen said.
‘I always encourage people to get as close as you can to the ideal.’