12/02/2013 04:57 pm ET Updated Feb 01, 2014

Obesity Is the New Cigarette

Haven't we learned that lifestyle choices make a difference to our risk of getting cancer?

If you are one of the unbelievers, go to the Globocan webpage (sponsored by the International Agency for Research on Cancer), where you can play with world data. You can enter countries of interest and see what the top cancers are in the country of your choice.

You will notice that there is great variation across the world. The differences are mainly due to lifestyle. In the U.S. and most of Europe where people have had a long history of smoking, you will see a high incidence of lung cancer; in places where smoking has not been part of the culture, such as Kenya, lung cancer is not a major killer.

It took us over 50 years to get the message to stop smoking. Over those years, many millions of people unnecessarily suffered and died due to lung cancer. It should be noted that not all lung cancers are caused by smoking, but about 90 percent of cases in the U.S. are caused by smoking.

Thanks to the forward-thinking of Jerry M. Reiss, a former city councilman of San Luis Obispo California, who first proposed a local public smoking ban, prohibition of smoking in public places became policy in many countries in the Western world.

Has the cessation of smoking made a difference?

The data from The American Cancer Society Cancer Statistics 2013 is beautifully obvious: Rates of mortality (See Figure 4) due to lung cancer are dramatically on their way down.

It must be said that although we have seen great progress in the field, cancer is still a hideous disease, and we should always want to do everything in our power to reduce its risk. Not smoking is a simple way of reducing lung cancer risk. We don't need to take drugs with toxic side effects or get injections to prevent it. All we have to do is put out the cigarettes.

So why are we setting ourselves up for another cancer epidemic, this time caused by obesity?

We are all aware of the obesity epidemic. The problem is much more serious than the issue of seating in airplanes or movie theatres. Obesity is linked to many cancers. An official report published by the American Institute for Cancer Research and the World Cancer Research Fund entitled "Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective" states that there is convincing evidence that body fatness increases the risk of postmenopausal breast, endometrial, esophageal, pancreatic, kidney and colon cancers.

Obesity is the new cigarette.

The proposed mechanisms of how obesity causes cancer includes the production of estrogen from fat cells, an increased level of insulin-like growth factors, the triggering of a chronic inflammatory response -- an emerging hallmark of cancer, and esophageal reflux.

An increased level of estrogen is a well-known risk factor for breast cancer. Lessons learned from early oral contraception formulas and hormone replacement therapies highlight the role played by increased estrogen in breast cancer risk.

New evidence published in Science (Nov. 29, 2013) shows a new biochemical link between obesity and breast cancer and it too, involves a link to estrogen.

Obese people often have elevated levels of cholesterol. Why is cholesterol important in relation to breast cancer? Not only is cholesterol a known starting point for the synthesis of estrogen but now new evidence puts an unsuspected cholesterol metabolite in the spotlight. Cholesterol is metabolized to 27-hydroxycholesterol (27HC) and this molecule was shown to mimic the growth-promoting effects of estrogen in breast cancers.

This was demonstrated in mice engineered to develop high cholesterol when fed a high-fat diet. When implanted with breast cancer cells, these mice had elevated levels of 27HC in their blood and significantly larger tumors compared to controls. The findings of this study also revealed that the mechanism of this effect is dependent on the estrogen receptor. This explains why obesity is a risk factor for estrogen receptor-positive breast cancer in postmenopausal women.

So what are we going to do about the epidemic of obesity so that another unnecessary epidemic of cancer is prevented? We must not bloat ourselves to an early death from cancer.

It's time to stop eating to excess and live active lifestyles into old age.