As obesity rates in the U.S. and the rest of the world continue to rise, so does the risk of certain types of cancer, according to a new study.
The large metastudy, conducted at the University of Manchester in England, examined data from more than 140 studies conducted worldwide that involved more than 280,000 people altogether. It concluded that obesity may increase the risk of a dozen various cancers.
In men, an average weight gain of 33 pounds increased the risk of esophageal cancer in men by 52 percent, thyroid cancer by 33 percent, and both colon and kidney cancers by 24 percent, according to the study.
In women, an average gain of 29 pounds was shown to increase the risk of uterus and gall bladder cancer by almost 60 percent, esophageal cancer by 51 percent and kidney cancer by 34 percent.
“There have been other studies that have suggested that obesity has been linked with different types of cancer, but it often takes a huge number of cases in order to show the statistical significance,” said Ben Douglas, medical director at the University Health Center. “That’s where studies like this are really helpful.”
The study doesn’t actually prove that being obese in itself causes these cancers, but there is a definite link, said Douglas.
“Obesity has a significant factor on hormone levels tied to different kinds of cancer,” Douglas said.
For example, overweight women have higher hormone levels in the breasts and the ovaries, which puts them at higher risk for cancer in these areas.
Sarah Wally, a registered dietitian at the American Institute for Cancer Research, said obese people are not only at a higher risk, but that lean people are automatically less prone to cancer.
“People who are leaner typically tend to be more physically active,” Wally said. “They also have a different dietary pattern: more plant-based foods and whole grains, less high-fat cheeses or fatty meats.”
Most people have a false perception of excess fat, Wally said. The fat doesn’t just “sit there”; it actively secretes proteins called pseudocholine. These proteins produce low-grade inflammation that may make people more susceptible to cancer. Overweight people can also develop insulin resistance, which causes higher levels of insulin to circulate in the body and can stimulate cancer development.
Douglas said the risk of esophageal cancer among obese people may be so high due to climbing rates of acid reflux.
This study may be of particular concern in Oregon. According to a state Department of Human Services report, cancer is the leading cause of death in Oregon, whereas in the United States, heart disease takes the lead. The report also stated that 59.7 percent of adult Oregonians were obese or overweight in 2005.
“There’s a lot of research that just the fact of being overweight is promoting cancer,” said Wally.
The good news is, college students whose metabolisms have just begun to slow down have the choice to prevent their risk now.
“You don’t want to have that negative outlook that everything causes cancer,” Wally said. “There are a lot of choices you can make in your life to prevent causing cancer. For example, people tend to gain about a pound a year once they reach adulthood, and when you’re 18 you think, ‘Oh, it’s just a couple pounds,’ but it builds. It really is never too early to start exercising, eating right and getting rid of that fat.”
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