Research has established a clear link between obesity and cancer. Obesity has also been shown to dim the prognosis for cancer patients. Studies suggest that obesity-related insulin resistance may increase the risk of cancer and that excess white fat allows cancer cells to thrive.
Obesity and tumor growth
To search for reasons why obesity promotes cancer risk and progression, scientists from the University of Texas Health Science Center at Houston investigated the theory that that white adipose tissue, a certain type of fat tissue that expands once people cross the obesity threshold, facilitates the growth and survival of cancer cells.
Results from experiments with mice supported the association. Researchers put groups of obese and lean mice on the same diet. Tumors grew much faster in the obese mice, which had far more adipose white tissue. This significant difference from the lean mice compelled the researchers to drill down on the specific activity of white fat cells, known as adipose stromal cells.
Feeding cancer cells
The presence of cancer released adipose stromal cells into the blood stream. Once they made contact with tumors, some of the cells developed into fat cells. However, others were put to use developing blood vessels that allowed cancer to flourish by increasing the flow of oxygen and nutrients to the tumors.
The study suggests that obesity feeds cancer cells. Other research suggests that insulin resistance, one of the more dangerous complications of obesity, increases the likelihood cancer will appear at the trough to be fed by adipose stromal cells.
Insulin growth factors and cancer
According to Dr. Edward L. Giovannucci, a nutrition and epidemiology professor at the Harvard School of Public Health, cancer may be linked to insulin resistance because the hormone plays a key role in the growth of body tissues.
Cells in the body use insulin to convert sugar into energy. When a high sugar, high carbohydrate diet stimulates the overproduction of insulin over the years, cells overloaded with the hormone lose their capacity to use it. Excess insulin flows into the bloodstream. Insulin resistance sends the body down the road to diabetes.
Insulin resistance doesn’t diminish the growth promoting properties of insulin. High levels of insulin in the blood may make cells more sensitive to other growth factors, such as cancer. The excess insulin could signal cancer cells, which have the ability to grow uncontrollably, to proliferate.
Diabetes cancer link
Several studies have found that people with higher levels of insulin in their blood are at increased risk for developing colon, pancreatic, kidney, premenopausal breast, and aggressive prostate cancers. In particular, risk factors for colon cancer are very similar to those for diabetes, including obesity, belly fat, physical inactivity and a diet high in saturated fat, refined carbohydrates and sugars, and low in fiber.
It’s likely that scientists in the employ of pharmaceutical companies will use data on adipose stromal cells and cancer to develop drugs that convert carcinogenic white fat into healthy brown fat. Researchers may also search for drugs that block the passage of adipose stromal cells into tumors.
For the rest of us, the implications of research into obesity, insulin resistance and cancer should be clear. A healthy diet and lifestyle is the most effective cancer prevention available. For those who are obese, losing weight is a matter of life and death.