A study of more than two million people showed that being overweight markedly increases risk for at least nine different cancers in men (bladder, colorectum, gallbladder, kidney, liver, lung, lymphatic system, pancreas, stomach) and eleven cancers in women (gallbladder, kidney, liver, lung, lymphatic system, ovaries, pancreas, stomach, uterus, cervix, and endometrium), as well as increased risk for death from any cause (PLoS Medicine, August 9, 2019).

Another study of more than six million cancer patients diagnosed between 2000 and 2016 found that obesity-associated cancers are occurring now at the highest rate ever recorded and that the most likely time to develop an obesity-associated cancer is between ages 50 to 64 (JAMA Network Open, August 14, 2019). Since many obesity-associated cancers take more than 20 years to develop, this study suggests that being overweight by age 30 puts a person at high risk for developing certain cancers in mid-life. Data from the U.S. Centers for Disease Control and Prevention show that obesity rates more than doubled among post adolescents from 1988 to 2016, rose up to 45 percent in those ages 40 to 59, and rose up to 40 percent among those aged 60 and up.

The American Association for Cancer Research reports that being overweight is linked to 25 percent of newly diagnosed cancer cases in the U.S. (Am Cancer Soc, Cancer Prevention & Early Detection: Facts & Figures 2017-2018). Adding lack of exercise and a pro-inflammatory diet increases the estimate to 33 percent. Overweight is associated with almost five million cancer deaths each year.

How Weight Gain Increases Cancer Risk
A study from Stanford showed that when people gained six pounds in one month, they suffered unhealthful changes in:
• genes in their cells,
• types of colon bacteria,
• heart-attack risk factors, and
• levels of inflammation.
After they lost the added weight, these indicators returned to normal (Cell, Jan 2018).

Increased cancer risk is associated specifically with belly fat (Circulation, 2008;117(13):1658–1667). Depositing fat in the liver can prevent the liver from doing its job of removing excess sugar from the bloodstream. This causes a high rise in blood sugar that  can cause sugar to stick to cells throughout your body and damage them. Your immune system responds to this cell damage in exactly the same way that it responds to invading germs, producing the same cells and chemicals called cytokines that are supposed to attack and kill germs. If your immune system stays active all the time,, it can use the same mechanisms that it uses to kill germs and heal injuries to attack your healthy tissues. See Inflammation Can Help or Harm. Your immune system can attack your genetic material, called DNA, that tells cells that they are supposed to divide a certain number of times and then die, having been replaced by new cells. However, if the DNA in cells is damaged, the cells can forget to die and keep on dividing. For example, breast cancer cells do not kill a person as long as they stay in the breast. They kill by becoming so abundant that they spread from the breast to invade and destroy your brain, lungs, bones and other organs. 

My Recommendations
• Maintain a healthful weight, and if you are overweight, work to lose the excess. I recommend Intermittent Fasting.
• Eat plenty of anti-inflammatory foods and restrict the pro-inflammatory foods.
• Drink only water, unsweetened coffee or tea; avoid drinks with calories, including fruit juices.
• Exercise regularly (Nature Reviews Cancer, 2008;8(3):205–211). The best way to stick with an exercise program is to exercise with a regular partner or in a group, such as a dance class, running club or bicycle club, spinning class, water volleyball group, or any other organized vigorous activity.