Weight gain raises colon cancer risk

Colorectal cancer, commonly known as bowel or colon cancer, is among the leading causes of cancer-related deaths in Kenya.

Previously associated with old age, the disease is increasingly being diagnosed among young people due to unhealthy diets and sedentary lifestyles. Among women, new research indicates that being overweight or obese doubles the risk of developing colorectal cancer before the age of 50.

Overweight individuals have a Body Mass Index (BMI) of between 25 and 29 while those with a BMI of more than 30 are considered obese. For a healthy weight, it is recommended that people have a BMI of between 18 and 24.

The new research, which was published in the JAMA Oncology Journal is among the first epidemiologic (population wide) studies to analyse the potential contributors to early onset colorectal cancer (happening below the age of 50).

It included data from more than 85,000 women in the US aged between 25 and 44 years. These women are participants of a health study that began in 1989. Therefore, the researchers were able to track their weight over the years.

Findings of the study, which was led by the Washington School of Medicine in St. Louis, showed that having a high BMI at 18 years and weight gain since early adulthood increased the risk of colorectal cancer under the age of 50.

"Our findings really highlight the importance of maintaining a healthy weight, beginning in early adulthood for the prevention of early onset colorectal cancer," said Dr Yin Cao, senior author of the study and cancer epidemiologist in the Division of Public Health Sciences at Washington University.

Though not at large-scale levels, previous studies have also linked weight gain to colorectal cancer in men.

Dr Andrew Odhiambo, a Nairobi-based consultant medical oncologist, noted that aside from diet, hereditary factors also increase people's chances of getting the disease.

Individuals with immediate family members such as parents or siblings that have suffered from colorectal cancer are highly likely to get it too.

The risk increases if more than one person in the family has the disease and if those affected got diagnosed when younger than 45 years. Suffering from ailments such as inflammatory bowel disease, which causes the colon to be inflamed over long periods of time can lead to colorectal cancer, especially if it is left untreated.

Research has also found that people with type 2 diabetes have an increased likelihood of getting the cancer and a less favourable outcome after diagnosis.

A personal history of polyps (non-cancerous swellings) in the colon or having suffered from colorectal cancer before — especially when one is young — can cause those affected to be susceptible to the ailment.

Risk factors of this cancer that are preventable include obesity, smoking, physical inactivity, heavy alcohol use, diets high in red meat like beef and pork, as well as processed meats such as sausages and bacon.

Just as is the case with most cancers, Dr Odhiambo stated that early diagnosis of the disease enhances treatment outcomes and survival rates of those affected.

"We now have new medicines and better screening techniques. So if the cancer is detected at stage one or two, the disease can be effectively cured with just surgery and minimal chemotherapy."

According to him, early screening is a potent prevention strategy against colorectal cancer as it may detect polyps, which can be removed before they become cancerous. The screening may be done through a faecal occult blood test (FOBT) where doctors check for the presence of blood in stool.

However, this test is not 100-percent accurate as not all colorectal cancers cause bleeding in the bowel. And bleeding may not happen all the time.

Blood may also be present in stool due to other conditions such as haemorrhoids. Certain food types could also suggest blood in the colon when none is actually present.

A more advanced test known as colonoscopy is best suited for diagnosing colorectal cancer.

This technology allows doctors to look inside the entire rectum and colon for any abnormal growths or swellings, using a flexible lighted tube known as a colon scope that is inserted in the colon.

During the procedure, they can also remove tissue samples for further laboratory examination, which can confirm cancer diagnosis.

Generally, it is recommended that beginning the age of 50, both men and women should undergo a colonoscopy test. But those at high risk for the cancer should begin screening much earlier, based on advise from their doctors.

Apart from blood in faeces, other symptoms of colorectal cancer are diarrhoea, a feeling that the bowel does not empty properly, pain or bloating in the abdomen, unexplained weight loss, fatigue or tiredness, a lump in the abdomen as well as feeling full even when one has not eaten for a while.