Where you store fat, as opposed to how much you have, may be a better predictor of whether you’re at risk of colon cancer.

Researchers found they could catch twice as many cases if they measured people’s waist and hip sizes, rather than their body mass index (BMI).

Individuals classified as having an ‘apple shape’, characterized by a larger belly and narrower hips, faced a 40 percent higher risk of being diagnosed compared to those with a ‘pear-shaped’ body.

By comparison, when looking solely at BMIs, patients with the highest BMI were 23 percent more likely to develop colon cancer than those with the lowest.

The study of nearly half a million adults suggests that being ‘centrally obese’ is more dangerous than how much you weigh.

This increased risk could be due to a type of body fat called visceral fat surrounding organs like the colon and creating harmful inflammation, which can lead to cancer cell growth. 

BMI is simply a person’s weight compared to their height and is used around the world to help determine if a person is underweight or overweight.

However, the researchers said BMI doesn’t catch cancer cachexia, a phenomenon found in three in four colon cancer patients that causes them to lose muscle without fat. 

Researchers suggested having more fat around your belly and hips could raise colon cancer risk (stock image)

A 2023 study found that the distribution of someone’s fat was more important to their overall fat than just their body weight. Fat around the midsection, which stresses crucial organs, led to increased risk of diseases that could lead to premature death

Since BMI doesn’t distinguish between muscle and fat, it can make a person seem thinner even if they have larger amounts of body fat and could classify a fit person as overweight or obese due to having more muscle.

Waist and hip measurements, however, do not reflect muscle loss, so the researchers suggest they could be better indicators of central obesity.

For reasons such as this, experts have called on health authorities to move away from BMI and focus instead on body roundness index (BRI) to determine risks of diseases like heart disease and diabetes. 

The study comes as colon cancer has surged in the US over the past two decades, with healthy people in their 20s and 30s increasingly being getting the disease.

Just over 160,000 Americans are struck by the disease every year, and 50,000 die.

In the UK, 44,000 Brits are diagnosed each year, and there are roughly 16,800 deaths.

Experts are racing to find the cause and the risk factors that could help them work out who’s the most at risk.  

Researchers writing in JAMA Network Open have found that where people store fat may play a greater role than weighing more overall. 

The researchers looked at 458,543 adults ages 40 to 69 from the database UK Biobank.

The team followed up with participants regularly for 14 years.  

The participants were divided into four groups based on BMI, waist circumference, and waist to hip ratio. 

Waist circumference is the distance around your waist, just above the hips, and is used to measure belly fat.

The waist-to-hip ratio, meanwhile, compares waist circumference to hip measurements. 

Under the BMI system, a score of 18.5 to 25 is healthy. A score of 25 to 29 counts as overweight, and 30-plus means a person is obese, the stage at which chances of illness rocket

Hollywood hunk or hulk? Muscular celebrities like Dwayne ‘The Rock’ Johnson, Vin Diesel and Arnold Schwarzenegger are deemed obese under the Body Mass Index formula which is widely used by health authorities around the world. Some scientists are now arguing it should be replaced. Figures for Mr Schwarzenegger are from his ‘peak’ as a bodybuilder

BMI groups ranged from 24 to 30. A BMI from 25 to 29 is considered overweight, and over 30 is obese. 

For waist circumference, groups for women were defined as 29 inches or less, 29 to 32 inches, 32 to 36 inches, and 36 or more inches.

For men, these waist circumferences ranged from 35 inches or less, 35 to 38 inches, 38 to 40 inches, and 40 inches or more. 

Waist-to-hip ratios for women were broken into the following groups: 0.77 or less, 0.77 to 0.81, 0.81 to 0.86, and 0.86 or more.

For men, these were 0.89 or less, 0.89 to 0.93, 0.93 to 0.98, and 0.98 or more.  

According to the CDC, the average waist circumference for women is 39 inches and 40.5 inches for men.

Most women have a waist-to-hip ratio of 0.8. This is around 0.9 for men. 

The team said storing weight around the waist ‘showed a stronger and more consistent association’ with colon cancer risk than BMI did.

Overall, they found 17 percent of colon cancers could be attributed to high waist circumference and waist-to-hip ratio, or about one in six. 

Meanwhile, a high BMI was tied to 10 percent. 

The researchers wrote: ‘These findings suggest that central obesity metrics are likely to more comprehensively reflect the proportion of colorectal cancer cases attributable to obesity.’ 

The team also found women with the highest waist circumferences had a 22 percent increased risk of colon cancer, while men had a 53 percent greater likelihood. 

Meanwhile, women with the largest waist-to-hip ratios were 24 percent more likely to develop colon cancer compared to a 59 percent increased risk in men. 

The stark gender difference could be because men tend to store more fat around their mid-section than women, while women carry it more around the hips and buttocks 

Based on the findings, the researchers estimated one in six colon cancers in the study could be blamed on high waist circumference and waist-to-hip ratios. 

The team said: ‘On the basis of our results, higher proportions of CRC cases were attributable to excess weight than commonly assumed, and central obesity had greater relevance regarding obesity-related CRC incidence.’ 

The researchers recommended focusing on waist circumference and waist-to-hip ratios over BMI when calculating BMI risk. 

They also noted their findings ‘underline the importance of efforts to limit and overcome the obesity epidemic in CRC prevention.’