There is already strong evidence to link obesity with five types of cancer. A recent study conducted by International Agency for Research on Cancer reviewed more than 1,000 reports, and in doing so has found strong evidence in eight further cancer types that are caused by obesity. These include gastric, liver, gallbladder, pancreatic, ovarian, thyroid, blood (multiple myeloma) and brain (meningioma) cancers.
An estimated 640 million adults and 110 million children and adolescents were obese globally in 2013. According to the chairman of IARC Dr Graham Colditz, a professor of medicine and surgery at Washington University in St Louis has said that these 13 types of cancer account for 42% of all new cancer diagnoses. Cancer is the second leading cause of death, according to Centers for Disease Control and Prevention. The study was published in the New England Journal of Medicine on 25th August, 2016.
Obesity is defined as the excess of weight on a person’s body and can be measured using the body mass index (BMI) which is calculated as weight of a person in kilograms divided by the square of a person’s height in meters. Among adults, overweight is defined as a BMI of 25.0 to 29.9 and obesity as a BMI of 30 or more. Obesity can further be divided into class 1 (BMI, 30.0 to 34.9), class 2 (BMI, 35.0 to 39.9), and class 3 (BMI, ≥40.0)
In 2013, an estimated 4.5 million deaths worldwide were caused by overweight and obesity. On the basis of recent estimates, the obesity-related cancer burden represents up to 9% of the cancer burden among women in North America, Europe, and the Middle East. What’s important to know is that most of the excess weight gain is largely determined by modifiable risk factors, such as excess diet and physical inactivity.
Researchers in this study also attempted to quantify the risk for obese people to develop this variety of cancers. They found that obese people were 1.8 times, 4.8 times and 7.1 times more likely to develop liver cancer, esophageal adenocarcinoma and uterine cancer, respectively. They also confirmed that for some of these cancers, as your weight goes up, so does the risk.
What justified the results of this study was how consistent the results were across different regions. Even trials that studied patients on the basis of waist measurements were consistent with trials that considered patients’ BMI. Waist circumference and body-weight gain in adulthood were also positively associated with the risk of postmenopausal breast cancer.
The association between BMI and endometrial cancer was particularly pronounced for type 1 endometrial cancer. There was a strong dose-response relationship, with relative risks of approximately 1.5 for overweight, 2.5 for class 1 obesity, 4.5 for class 2 obesity, and 7.1 for class 3 obesity. A modest positive association was observed for epithelial ovarian cancer, with a relative risk of 1.1.
The researchers also investigated the BMI data in adolescents and young adults less than or equal to 25 years to assess whether BMI at those ages increased risk of cancer in later ages of their life.
Positive associations were reported for several cancers that were also known to be associated with increased adult BMI, with the notable exception of postmenopausal breast cancer. The associations were generally similar to those with adult BMI, albeit some differences in magnitude and patterns.
The researchers further investigated the effects of body fat on cancer reoccurrence and survival after diagnosis. They managed to observe considerable variation in study design, setting, and timing of body-fatness measurement relative to cancer diagnosis. There was a large volume of evidence supporting an association between increased BMI near the time of cancer diagnosis and reduced survival in patients with breast cancer, whereas evidence for other cancers was sparse and less consistent. What’s interesting to note is that variation in diet affected cancer recurrence since a low-fat diet intervention led to a modest weight loss, resulting in a reduction in breast-cancer recurrence.
After observing individuals who reduced weight by undergoing bariatric surgery, the study suggested that intentional weight loss may reduce cancer risk, notably for breast and endometrial cancer There was however insufficient data to clearly link these observations and form a clear evaluation.
The researchers further explored all the cellular biological mechanisms involved in obesity-related cancers and concluded that obesity was associated with substantial metabolic and endocrine abnormalities, including alterations in sex hormone metabolism, insulin and insulin-like growth factor (IGF) signaling, and adipokines or inflammatory pathways.
The team concluded that the presence of excess body fat increased the risk of many cancers. Moreover, a review of this link in animal models and detailed exploration of this link at the cellular/molecular level produced a causal cancer-preventive effect of intentional weight loss, although evidence in humans remains to be established.
The obesity crisis has gone so out of hand and with these latest findings, government agencies are looking to intervene to try to take back control and deal with this growing problem. One good example of such interventions is that the Food and Drug Authority (FDA) has started approving medical devices that help prevent obesity from reaching pandemic levels.
One of the devices approved by FDA is called Reshape Dual Balloon System, a balloon based obesity treatment, which was approved back in 2015. The most recent obesity-fighting medical device to get approval from the FDA is AspireAssist.