What We’re Learning About The Connection Between Cancer + Obesity

Dr. Jason Fung is the author of The Cancer Code: A Revolutionary New Understanding of a Medical Mystery, a new book that breaks down emerging science on cancer research and pokes holes in our current approach.

According to Dr. Fung, cancer researchers may be focusing too much on genetics, what he terms the “seed” of cancer, at the expense of examining the “soil,” or the conditions under which cancer flourishes.

In this day and age, the science on cancer and prevention is moving faster than most of us can keep up with. Books like Dr. Fung's are invaluable to help us assess what's being studied and move quickly to make adjustments in a preventative lifestyle. 

We're running a series of excerpts from The Cancer Code, including this one on the newly flagged connection between cancer and obesity... 

It may sound trivial, but these four bits of knowledge cost, literally, hundreds of millions of dollars of research money and many decades of work:

+  Diet plays a large role in cancer.
+ Cancer is not caused by lack of dietary fiber.
+ Cancer is not caused by too much dietary fat.
+ Cancer is not caused by a vitamin deficiency.

These four conclusions left unanswered the most important question of all:

"What component of the diet is responsible for so much cancer?"

Beginning in the late 1970s, one nutritional measure began to eclipse all others in importance: obesity. The obesity epidemic began as an American phenomenon, but it has since gone global.

Cancer is increasingly known as an obesity-related disease, accounting for 20 to 30 percent of the risk of common cancers. Cancer in young adults is a warning for future disease burden. If you think it’s scary now, wait until this generation gets older. The obesity epidemic is affecting younger and younger patients, and cancer is following closely behind.

For example, the rate of pancreatic cancer is increasing by 0.77 percent per year for those ages forty- five to forty- nine, but for those ages twenty- five to twenty- nine, it is increasing six times more quickly. The youngest people are facing the steepest rises in cancer rates. By contrast, most cancers not related to obesity are decreasing, especially those related to viruses, smoking, and HIV.

"If weight gain increases cancer risk, does weight loss lower it?"

The first animal studies that suggested this possibility were published over a century ago, by 1914 Nobel laureate Peyton Rous. In mice, severely restricting food availability cut their risk of cancer by half. (1)

In the 1940s, Dr. Albert Tannenbaum, former president of the American Association for Cancer Research, discovered that, astoundingly, carbohydrate restriction alone in mice provided greater protection against cancer than overall calorie restriction. He concluded that “tumor formation is dependent on the composition of the diet, as well as the degree of caloric restriction,” a remarkably prescient observation. In the Nurses’ Health Study, women who lost ten kilograms or more after menopause and kept the weight off lowered their risk of breast cancer by an astounding 57 percent.

"Obesity clearly increases the risk of cancer."

Obesity also clearly increases the risk of type 2 diabetes. What is the link? The master hormone of metabolism: insulin.  

While today we think of insulin as a metabolic hormone, in primitive organisms, its primary function is as a growth hormone, regulating cell proliferation and survival. As we evolved into multicellular organisms, insulin evolved a second role as a nutrient sensor. This makes perfect sense, if you think about it, as growth always requires nutrients. When food is available, cells should grow. Make hay while the sun shines. When food is not available, cells should not grow. 

Using the exact same molecule (insulin) as both a growth factor and a nutrient sensor solves this fundamental coordination problem. When we eat, insulin goes up, which signals the availability of nutrients, and also signals the body to grow. Excessive nutrient sensing means excessive growth, a condition of obvious importance to cancer. Growth and nutrition/metabolism were now inextricably connected through the nutrient sensor insulin. A disease of excessive growth (cancer) is also always a disease of metabolism. Thus, hyperinsulinemia overstimulates the growth pathways and predisposes the body to diseases of excessive proliferation.

While there is no miracle food or diet that can keep cancer at bay, dietary prevention of cancer boils down to one key strategy: avoiding diseases of hyperinsulinemia, including obesity and type 2 diabetes. Intermittent fasting has also been shown to be a promising nutritional approach for cancer prevention, as it protects against many of the risk factors, such as obesity, type two diabetes and inflammation. Fasting during chemotherapy may also reduce the side effects of treatment while increasing efficacy. 

(1) Reference:. A. Tannenbaum, “The Dependence of Tumor Formation on the Composition of the Calorie-Restricted Diet as Well as on the Degree of Restriction,” Cancer Research 5, no. 11 (1945): 616–25.

For all medical references and for the full scope of Dr. Fung's research, see The Cancer Code published by Harper Collins. 

The Chalkboard Mag and its materials are not intended to treat, diagnose, cure or prevent any disease. All material on The Chalkboard Mag is provided for educational purposes only. Always seek the advice of your physician or another qualified healthcare provider for any questions you have regarding a medical condition, and before undertaking any diet, exercise or other health-related programs.

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