Medical professionals used to encourage people to stop smoking, as smoking used to be considered one of the leading causes of cancer. That’s now being overtaken by obesity, according to Surgical oncologist Dr. Wesley Francis.

“Obesity is an under-recognized contributor to cancer burden,” said Dr. Francis who spoke at the most recent Doctors Hospital Distinguished Lecture Series where he addressed the link between obesity and cancer.

This as studies in the United States (US) and the United Kingdom have linked increased weight to cancer risk. And it is estimated that one our of every three cancer deaths in the US is linked to excess body weight, poor nutrition and/or physical inactivity.

“The whole question of non-communicable diseases (NCD) is a big issue in the country and in the world. Basically, 38 million people die each year from NCD’s — cardiovascular disease, cancers, chronic respiratory disease and diabetes. And over 14 million deaths occur between the ages of 30 and 70. The majority of these deaths occur in developing countries. The Bahamas is still considered a developing country. NCDs really dominate the main cause of deaths in our country.”

In the 1990’s and early 2000’s he said most men and women were dying from HIV. Today he said HIV can be treated, but that for men, death is mostly due to ischemic heart disease; assaults, particularly in males; hypertensive disease, chronic non-communicable diseases and prostate cancer. For women he said mortality indicators include hypertensive disease, cerebral vascular disease (stroke), malignant neoplasm (cancers), and all lifestyle-related diseases or NCD’s. And that The Bahamas had the highest percentage in The Bahamas of premature deaths among males among the English speaking Caribbean and the Americas —the result he said of non-communicable diseases.

Taking into account the Americas, the surgical oncologist said The Bahamas again dominated in spending as it relates to health care when life expectancy is compared

Can you handle the truth?

“The truth is obesity is what is causing all of this issue with chronic NCDs,” said Dr. Francis. “Hippocrates 2,500 years ago called this corpulence, and said it’s not only a disease itself, but a harbinger of other diseases. It is now one of the greatest global threats — even Ebola can’t touch this one.”

The surgical oncologist defined obesity as a state of excess adipose (fat) tissue, defined by body mass index (BMI), which is calculated by a person’s weight divided by their height.

People with normal weight have BMI anywhere from 19 to 25; an overweight person has a BMI between 26 and 30; people who are considered obese have a BMI of 30 to 45; and the super obese are those people with a BMI greater than 45. According to the doctor, it can also be defined based on a person’s percentage of body fat. In men if 25 percent of their weight is body fat they’re considered obese; if 32 percent of a woman’s body weight is fat, she is considered obese.

He also said the fat distribution in the body is also a factor. And that when a person has fat distributed in their trunk, he said they are abdominal or visceral obese which causes the major issue because it has a number of metabolic issues associated with it including a low-grade chronic inflammatory state. This he said is most commonly seen in men. In the medical profession it is known as an android obesity — a large abdominal girth.

Gynecoid obesity, which he said men like to see in women is an excess accumulation in the gluteal area and buttock area. According to the doctor, this type of fat distribution is not associated with the adverse affect as when a person has more of a truncal or abdominal visceral obesity.

Worldwide, obesity has doubled since the 1980s, according to the doctor with more than 1.9 billion adults considered overweight; 600 million considered obese; and 42 million children under the age of five were overweight in 2013.

“Obesity is an under-recognized contributor to cancer burden. We used to tell people to stop smoking, as smoking used to be considered one of the most leading causes of cancer — that’s now being taken over by obesity,” said Dr. Francis.

The link

There are several mechanisms which link obesity to cancer according to the surgical oncologist.

“Obesity increases your risk and then even after you’ve had cancer and been treated, it increases the chance of it coming back. It also increases the chance of you dying from early stage cancer, meaning early stage cancer which a normal person would be easily treated and recover from, if you’re in the obese category, chances are you would have a higher risk of dying from that cancer itself,” he said.

In a UK population cancer study, Dr. Francis said a population of healthy people were studied to see what would happen if they just had a one kilogram per meters squared population wide increase in BMI.

“So if a BMI went from 29 to 30, they were then able to predict how many cancers would have developed. For one year they estimated that almost 600 cases of colon cancer were developed. And it was pretty uniform with predominantly most of the cancers — liver, gall bladder, breast, especially in post-menopausal women — cervical cancer, uterine cancer, ovarian cancer, kidney cancer over the entire population.”

Dr. Francis said the study concluded that BMI was associated with cancer risk within a population.

“It is estimated that one kilogram per meters squared population wide increase in BMI would result in almost over 4,000 additional cancer cases annually. So that means if our population increased by just one kilogram per meters squared, this is what the effect of that would be.”

Dr. Francis said the economic burden of this would be tremendous.

In a 2007 US study the doctor said that over 50,000 new cancer cases were seen in women and 34,000 new cases in men — and that all were attributed to just obesity.

“The National Cancer Institute estimated that by 2030 there would be 500,000 additional new cases in the US. That’s more than our population, so just think about it from our perspective. If we continue to have the issue with obesity and if we apply these numbers per capita to our population, what it would be like,” he said.

Obesity results after consuming extra food and a decreased energy output, and an increase in adipose (fat) tissue cells that he said aren’t just occupying space like matter, but become an organ to themselves.

“This landmass of tissue start to produce hormones and pro-inflammatory cytokines which are hormone-like substances — some are helpful and some are harmful. So that large fat mass actually produces harmful cytokines because it produces inflammation. Inflammation that continues unchecked leads to the development of cancer, and so this large tissue mass creates a chronic low-grade inflammatory state and it continues to lead on to cancer.”

Secondary associations

Secondary associations he said would include people who tend to have a lot of gallstones, and noted that there is a relationship between gallstones and obesity, and also a relationship between gallstones and gallbladder cancer.

“We know for certain, gastric cancer has been increasing worldwide, but the increase was associated with those cancers that were more in the proximal part of the stomach, and that is associated with GERD (gastroesophageal reflux disease), and GERD is associated with obesity. So there is a direct correlation between obesity, GERD and then the development of cancer,” he said.

The doctor said when he was in medical school, liver cancer was only spoken about as having been produced by viruses and alcohol, people getting cirrhosis of the liver, but now they have what is known as non-alcoholic fatty liver disease which can develop based on the amount of fat a person has in the liver.

“It had to be given a term because most of the liver disease was produced by alcohol, but now it’s non-alcoholic fatty liver disease,” he said.

The link between obesity and cancer starts with people’s diet — increased quantity and decreased quality and energy expenditure. He said increased exercise is a protective mechanism.

“If you decrease exercise then you have all this positive energy balance that is stored up. This then leads to this obesity. Decreased energy activity, you have just lost the anti-cancer effect, and then with poor quality diet, you ingest all of these carcinogens. All of these lead to increased cancer risks.”

Dr. Francis said one of the simplest definitions of cancer is a cell that does not die.

“Every cell in your body has a programmed day of death. You change the cells on your skin every day. You change the cells on the lining of your mouth everyday. You don’t change your heart cells every day. You don’t change your brain cells every day, but cancer cells have what we call this autonomous growth and what signals that mechanisms to that autonomous growth is all of these hormones. In a large mass of obesity cells or fat cells, it just increases the environment for the cells to become autonomous.

“This large mass of adipose tissue has weight and takes up space. It functions. And when it functions it produces adipokines which are not supposed to circulate in the body, and all of these increase risk and continue to act on these cells to have increased cell survival which leads to autonomous growth which leads to cancer.”

Dr. Francis said these normal fat cells take on a life unto themselves, producing extra insulin resulting in insulin resistance and people getting diabetes. He said the hormones produce leads to chronic pro-inflammatory state, and the body going into in a state of steady, slow inflammation.

In post-menopausal women estrogen is produced from the fat cells, according to the doctor. And that in an obese state, a female gets all of the estrogen being produced in the fat cells which then promotes the continued survival of breast cancer cells. He said the cells also produce insulin, which increases and produces a pro-inflammatory state, causing cell survival, and cell proliferation. It causes angiogenesis (production of blood cells) and when a person has angiogenesis within this, the cancer cells are able to spread.

In a post-menopausal female colon cancer, breast cancer, endometrial, renal and liver cancer all are increased when the BMI increases. Obese men seem to be at an increased risk of biologically aggressive prostate cancer. He said that there is a higher mortality in men and higher in women when there is obesity. He said that a BMI greater than 35 is associated with increased risk of colon cancer mortality; and that overall, 14 percent of cancer deaths in men and 20 percent of cancer deaths in women are associated with obesity.

It’s all about choice

“In The Bahamas we have a unique problem, particularly with women with breast cancer. We have a hereditary component. If you’re born with the breast cancer gene there’s nothing you can do about that if you’re born with that, because you can’t change your parents, you can’t change your genetics. But there are things you can change and these are the modifiable risk factors that we want to talk about.”

Taking away the obesity and cancer link the doctor said is all about choice and what people decide to do. He said modifiable causative risk factors for NCDs and cancer include making a choice to stop tobacco use, stop consuming unhealthy diets, and to do away with physical inactivity and harmful use of alcohol. Becoming less obese as a population he said has to start with the children who are the next generation. He said a shift in culture should affect them as they grow up as far as nutrition labeling and establishing nutritional guidelines, and letting children know what is healthy and what is not.

“Obviously everybody has to take responsibility for themselves, but also there has to be a corporate responsibility and I would say a multi-sectorial — government’s involved and private sector’s involved, but a change in culture.”

Even though he’s a surgeon oncologist who loves his job, Dr. Francis said preventing cancer would work far better than what he does in terms of trying to cure it.

“It’s going to take a lot of things, and it’s not an easy problem to fix, but I think if you start somewhere, then you can,” he said.