A study has found that a protein released from fat in the body can cause non-cancerous cells to turn into cancerous ones, and that fat around the stomach releases even more of this protein that other types of fat. This is the latest in a series of studies warning of the danger of having excess fat around the vital organs.
Fat cells
Researchers from the US have looked at ‘visceral adipose tissue’ – the fat that coats the internal organs – and how it could be linked to cancer, using both research on mice and on human fat cells in the laboratory.
They fed mice a high-fat diet and then induced cancer using ultraviolet B rays. On analysing the fat cells, they discovered that visceral fat releases a protein called ‘fibroblast growth factor-2’ (FGF2), which then stimulates the growth of epithelial cells, which can turn malignant (cancerous). Visceral fat produced more of this FGF2 than subcutaneous fat (fat that is just under the skin).
They also found that FGF2 drives skin and breast cells that were already vulnerable to the protein to transform into cancerous cells. This led the researchers to conclude that visceral fat can make healthy cells transform into malignant cells.
Visceral fat
Belly fat (visceral fat) is fat that is inside the abdominal cavity and which coats the internal organs, such as the heart, liver, pancreas and intestines. This is different to ‘subcutaneous’ fat, which sits directly beneath the skin.
Visceral fat plays a significant role in how our hormones function, as it disrupts our metabolism. It has long been known that having high amounts of this type of fat is associated with increased risk of health problems such as type 2 diabetes, heart disease and Alzheimer’s disease.
The problem with visceral fat is that you can’t see it. However, it is likely that people who have subcutaneous fat around their belly are likely to have high levels of visceral fat. Waist size can be a predictor of the amount of visceral fat someone carries.
Body mass index
Previous studies have shown a link between visceral fat and cancer, but this study looked at exactly why there may be this link.
The discovery that excess visceral fat stimulates healthy cells to develop into cancerous ones through FGF2 levels is key, as it could lead to cancer prevention strategies that stop FGF2 production, or treatment for people who already have cancer that involves blocking FGF2.
The research also throws doubt on using the body mass index (BMI) to tell us about our health risks. Professor Jamie Bernard from Michigan State University said: “Our study suggests that body mass index may not be the best indicator.
“It’s abdominal obesity, and even more specifically, levels of fibroblast growth factor-2 that may be a better indicator of the risk of cells becoming cancerous.”
Waist-to-hip ratio
There has recently been doubt thrown on the use of BMI to quantify health, particularly as the amount of muscle someone has can give them a high BMI.
The NHS has advised people to look at waist size, as well as BMI. They recommend that a healthy waist circumference for men is less than 94cm (37 inches) and, for women, less than 80cm (32 inches). There are also waist-to-hip ratio calculations that divide the circumference of the waist by the circumference of the hips, which can provide an assessment of the amount of belly fat a person has.
Previous research has found that people with a normal BMI but a larger waist-to-hip ratio are at an increased risk of health problems compared to people with a smaller waist-to-hip ratio with either a similar or higher BMI.
Biggest health impact
This latest study around cancer and belly fat adds to the theory that it’s not how much fat you have on your body, but where you carry it which impacts the most on your health and risk of health problems. And that high amounts of visceral fat can not only lead to health problems such as diabetes and heart disease, but can in fact cause cancer.