Science Weighs in On How Fat Raises Cancer Risk

Scientists have known for years that obesity can rise cancer risk, but how? Now, new research offers clues to how fat cells encourage tumors.

The issue is an important one, the study author said.

“Obesity is increasing dramatically worldwide, and is now also recognized as one of the major risk factors for cancer, with 16 different types of cancer linked to obesity,” explained Cornelia Ulrich, of the Huntsman Cancer Institute in Salt Lake City.

To help prevent the disease, “we urgently need to identify the specific mechanisms that link obesity to cancer,” she said.

Prior studies have already outlined several ways fat could play a role in cancer. For example, obesity increases inflammation in the body, which has long been associated with the disease.

Obesity can also affect cancer cell metabolism and undermine the immune system’s natural defenses, which may help tumors to grow and spread.

Ulrich’s team noted that the link between fat and cancer also hinges on cellular “crosstalk” — changes in complex chemical signaling within cells. Finding ways to interrupt this “crosstalk” could lead to new ways to help prevent cancer, the researchers theorized.

In the new review, to be published Sept. 5 in Cancer Prevention Research, an international team of researchers looked at data from 20 existing studies. The studies were published over the past seven decades, and each focused on cellular crosstalk between fat cells and malignant tumors.

In several of these studies, certain fat cells — known as “adipose stromal cells” — were able to invade cancer lesions and then help spur the growth of tumors. The data also showed that obese people with prostate or breast cancer appeared to have more of these cells than thinner people.

Some types of fat cells are also more “metabolically active,” releasing more substances that promote tumor growth, the review found.

Also, fat may be white, brown or beige, Ulrich’s team noted. And these different types of fat each behave differently, depending on quantity and location in the body. For example, the review found that white fat tissue is linked with inflammation and worse outcomes for women with breast cancer.

The location of fat in the body also influences how it affects certain types of cancer, the review found. Fat tissue is usually adjacent to colon and rectal cancers, the research team noted, and it is part of the direct environment of breast tumors.

According to the team, future studies might help doctors figure out if it’s possible to disrupt the processes that promote the growth of tumors by affecting nearby fat.

“We are just beginning to unravel the ways crosstalk occurs and the substances involved,” Ulrich said in a journal news release. “The more we understand this process, the better we can identify targets and strategies for decreasing the burden of obesity-related cancer.”

Two experts in obesity agreed that this type of research is important.

“Obesity is going to surpass cigarette smoking as the leading cause of cancer deaths,” said Dr. Mitchell Roslin, chief of obesity surgery at Lenox Hill Hospital in New York City.

“The take-home message here is that proper nutrition and maintaining a proper weight is essential for successful preventative health,” he said. “Obesity is not inert and impacts virtually every aspect of your body, and not in a positive manner.”

Dr. Raymond Lau is an endocrinologist at NYU Winthrop Hospital in Mineola, N.Y. He said that “there has long been an association between obesity and cancer risk. There is growing evidence that inflammation is the common link between these two disease states, and this review article helps to strengthen this relationship.”

Source : HealthDay


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Study Shows How Food Preservatives May Disrupt Human Hormones and Promote Obesity

Can chemicals that are added to breakfast cereals and other everyday products make you obese? Growing evidence from animal experiments suggests the answer may be “yes.” But confirming these findings in humans has faced formidable obstacles — until now.

A new study published today in Nature Communications details how Cedars-Sinai investigators developed a novel platform and protocol for testing the effects of chemicals known as endocrine disruptors on humans.

The three chemicals tested in this study are abundant in modern life. Butylhydroxytoluene (BHT) is an antioxidant commonly added to breakfast cereals and other foods to protect nutrients and keep fats from turning rancid; perfluorooctanoic acid (PFOA) is a polymer found in some cookware, carpeting and other products; and tributyltin (TBT) is a compound in paints that can make its way into water and accumulate in seafood.

The investigators used hormone-producing tissues grown from human stem cells to demonstrate how chronic exposure to these chemicals can interfere with signals sent from the digestive system to the brain that let people know when they are “full” during meals. When this signaling system breaks down, people often may continue eating, causing them to gain weight.

“We discovered that each of these chemicals damaged hormones that communicate between the gut and the brain,” said Dhruv Sareen, PhD, assistant professor of Biomedical Sciences and director of the Induced Pluripotent Stem Cell Core Facility at the Cedars-Sinai Board of Governors Regenerative Medicine Institute. “When we tested the three together, the combined stress was more robust.”

Of the three chemicals tested, BHT produced some of the strongest detrimental effects, Sareen said.

While other scientists have shown these compounds can disrupt hormone systems in laboratory animals, the new study is the first to use human pluripotent stem cells and tissues to document how the compounds may disrupt hormones that are critical to gut-to-brain signaling and preventing obesity in people, Sareen said.

“This is a landmark study that substantially improves our understanding of how endocrine disruptors may damage human hormonal systems and contribute to the obesity epidemic in the U.S.,” said Clive Svendsen, PhD, director of the institute and the Kerry and Simone Vickar Family Foundation Distinguished Chair in Regenerative Medicine.

More than one-third of U.S. adults are considered to be obese, according to federal statistics.

The new testing system developed for the study has the potential to provide a much-needed, safe and cost-effective method that can be used to evaluate the health effects of thousands of existing and new chemicals in the environment, the investigators say.

For their experiments, Sareen and his team first obtained blood samples from adults, and then, by introducing reprogramming genes, converted the cells into induced pluripotent stem cells. Then, using these stem cells, the investigators grew human epithelium tissue, which lines the gut, and neuronal tissues of the brain’s hypothalamus region, which regulates appetite and metabolism.

The investigators then exposed the tissues to BHT, PFOA and TBT, one by one and also in combination, and observed what happened inside the cells. They found that the chemicals disrupted networks that prepare signaling hormones to maintain their structure and be transported out of the cells, thus making them ineffective. The chemicals also damaged mitochondria — cellular structures that convert food and oxygen into energy and drive the body’s metabolism.

Because the chemical damage occurred in early-stage “young” cells, the findings suggest that a defective hormone system could impact a pregnant woman as well as her fetus in the womb, Sareen said. While other scientists have found, in animal studies, that effects of endocrine disruptors can be passed down to future generations, this process has not been proved to occur in humans, he explained.

More than 80,000 chemicals are registered for use in the U.S. in everyday items such as foods, personal care products, household cleaners and lawn-care products, according to the National Toxicology Program of the U.S. Department of Health and Human Services. While the program states on its website that relatively few chemicals are thought to pose a significant risk to human health, it also states: “We do not know the effects of many of these chemicals on our health.”

Cost and ethical issues, including the health risk of exposing human subjects to possibly harmful substances, are among the barriers to testing the safety of many chemicals. As a result, numerous widely used compounds remain unevaluated in humans for their health effects, especially to the hormone system.

“By testing these chemicals on actual human tissues in the lab, we potentially could make these evaluations easier to conduct and more cost-effective,” Sareen said.

Source : Cedars-Sinai


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Where Body Fat Is Carried Can Predict Obesity-related Cancer Risk

Scientists have found that carrying fat around your middle could be as good an indicator of cancer risk as body mass index (BMI), according to research published in the British Journal of Cancer.

It shows that adding about 11 cm to the waistline increased the risk of obesity related cancers by 13 per cent.

For bowel cancer, adding around 8 cm to the hips is linked to an increased risk of 15 per cent.

Carrying excess body fat can change the levels of sex hormones, such as oestrogen and testosterone, can cause levels of insulin to rise, and lead to inflammation, all of which are factors that have been associated with increased cancer risk.

This is the first study comparing adult body measurements in such a standardised way for obesity-related cancers.

Using a novel approach, scientists at the International Agency for Research on Cancer (IARC-WHO) showed that three different measurements of body size, BMI, waist circumference, and waist to hip ratio all predicted similar obesity-related cancer risk in older adults.

The study combined data from around 43,000 participants who had been followed for an average of 12 years and more than 1,600 people were diagnosed with an obesity-related cancer.

Dr Heinz Freisling, lead study author and scientist at the International Agency for Research on Cancer (IARC-WHO), said: “Our findings show that both BMI and where body fat is carried on the body can be good indicators of obesity-related cancer risk. Specifically, fat carried around the waist may be important for certain cancers, but requires further investigation.”

“To better reflect the underlying biology at play, we think it’s important to study more than just BMI when looking at cancer risk. And our research adds further understanding to how people’s body shape could increase their risk.”

Being overweight or obese is the single biggest preventable cause of cancer after smoking and is linked to 13 types of cancer including bowel, breast, and pancreatic.

Dr Julie Sharp, Cancer Research UK’s head of health information, said: “This study further highlights that however you measure it being overweight or obese can increase the risk of developing certain cancers, including breast and bowel.

“It’s important that people are informed about ways to reduce their risk of cancer. And while there are no guarantees against the disease, keeping a healthy weight can help you stack the odds in your favour and has lots of other benefits too. Making small changes in eating, drinking and keeping physically active that you can stick with in the long term can help you get to a healthy weight – and stay there.”

Source: Cancer Research UK


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Study Finds More Accurate Way to Determine Adolescent Obesity

Adam Pope wrote . . . . . . .

The body mass index calculations that physicians have been relying on for decades may not be accurate for assessing body fat in adolescents between the ages of 8 and 17.

A new study published today in the Journal of the American Medical Association Pediatrics shows that tri-ponderal mass index estimates body fat more accurately than the traditional BMI in adolescents.

These new findings are timely as diagnosing, treating and tracking the prevalence of children and adolescents with obesity is a high public health priority. Moreover, many school districts are sending home report cards labeling adolescents as overweight — a practice that has been controversial because children and adolescents tend to be more vulnerable to weight bias and fat shaming than adults.

bmi tmi graphic“Treating obesity in adolescents requires an accurate diagnosis first,” said lead scientist Courtney Peterson, Ph.D., an assistant professor in the School of Health Professions at the University of Alabama at Birmingham. “We found that TMI is both more accurate and easier to use than BMI percentiles. These new findings have the power to potentially change the way we diagnose obesity in children and adolescents ages 8 to 17.”

BMI is the standard used worldwide to screen for obesity in both children and adults, despite prior evidence that it does not work as well in adolescents. To test BMI accuracy in adolescents, researchers compared body composition data from 2,285 Caucasian individuals ages 8 to 29 who participated in the 1999-2004 U.S. National Health and Nutrition Examination Survey (NHANES). Their findings challenge the accuracy of BMI (weight in kilograms divided by height in meters squared) in adolescents and show that TMI (weight divided by height cubed) estimates body fat more accurately than BMI in those 8 to 17 years old.

“BMI is a pretty good tool for determining whether adults are overweight or obese,” Peterson said. “But we’ve always kind of known that it doesn’t work as well in children.”

Using three different calculations — stability with age, accuracy in estimating percent body fat and accuracy in classifying adolescents as overweight versus normal weight — researchers compared BMI to several different obesity indices. They found that TMI is the best overall body fat index to use in Caucasian adolescents between the ages of 8 and 17.

The researchers found that TMI better estimates body fat percentage, especially in male adolescents for whom the investigators found BMI to be particularly inaccurate. Their analysis also showed TMI to be a better index for diagnosing overweight adolescents than the current BMI percentiles. Using BMI percentiles, researchers noted that adolescents are incorrectly diagnosed as overweight 19.4 percent of the time, versus an only 8.4 percent incorrect overweight diagnosis rate for TMI. The data showed this is especially true for lean adolescents, a significant fraction of whom are incorrectly being diagnosed as overweight.

The researchers also used mathematical strategies to show how the relationship between body weight and height is much more complex in children and adolescents than it is in adults, particularly when adolescents are rapidly growing. The authors explained that for decades this complexity made it challenging to figure out the optimal body fat index for adolescents.

Steven Heymsfield, M.D., one of the team’s physician scientists at LSU’s Pennington Biomedical Research Center, added that, to make BMI work in children, complicated BMI percentiles called “Z scores” were developed to diagnose overweight status and obesity based on BMI levels specific to a child’s age and gender. But the researchers found that using percentiles does not solve BMI’s accuracy problems.


“These findings are important. Many school districts send home report cards labeling adolescents as overweight, and children and adolescents tend to be more vulnerable to weight bias and fat shaming than adults.”

— Courtney Peterson, Ph.D.


Peterson mentioned that percentiles are problematic because they change over time and can become outdated. However, she emphasizes that, even if BMI percentiles were updated to be as accurate as TMI for diagnosing adolescents as lean versus overweight, TMI still inherently estimates levels of body fat in adolescents more accurately than BMI does, while also eliminating the need for complicated percentiles.

“These findings are important,” Peterson said. “Many school districts send home report cards labeling adolescents as overweight, and children and adolescents tend to be more vulnerable to weight bias and fat shaming than adults.”

Obesity increases the risk of several chronic diseases in adults, including diabetes, cardiovascular disease and cancer. Children who are overweight are at an even higher risk than adults, and nearly one in six children in the United States is overweight. Several national and global initiatives are underway to screen and diagnose children who are overweight as a first step in curbing the obesity epidemic and the chronic diseases that follow.

Investigators agree that further research is needed to assess the effectiveness of TMI in broader audiences, including wider age ranges and ethnicities.

“We look forward to collaborating with other existing national and global health organizations to analyze additional data for diagnosing weight status among children and adolescents,” Peterson said. “Ultimately, we hope this research lays the foundation for improving the health of adolescents, and we think that down the road TMI will likely replace BMI for children and adolescents.”

Source: University of Alabama at Birmingham


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It’s Time to Ditch BMI for BVI as a Measure of Obesity

Laura Entis wrote . . . . . .

Body mass index has long determined what it means to be overweight. Invented in the early 1800s by a Belgian statistician, the measurement is used as a definitive benchmark: those with a score below 18.5 are underweight, those who fall between 18.5 and 24.9 are normal, those between 25 to 29.9 are overweight, and those 30 and higher are obese.

For years, medical professionals have taken issue with these cleanly drawn lines. The BMI scale, critics argue, is too simplistic to accurately reflect health on an individual basis.

Today, the Mayo Clinic adds its voice to the chorus. The medical care provider announced that is recommending a new system for measuring body composition and weight distribution: the Body Volume Indicator (BVI). Unlike BMI, which is formulated by comparing an individual’s weight in relation to his or her height, BVI considers “other crucial factors such as fat mass, lean mass, and weight distribution when determining an individual’s body composition,” Jose Medina-Inojosa, a cardiovascular research fellow at the Mayo Clinic, told Fortune. In addition to weight and height, information on waist-to-hip ratio, total body fat percentage, and abdominal volume is factored when determining a score.

These are harder metrics to measure than feet and pounds, of course, but technology has advanced since the 19th century. Select Research, a U.K.-based market research agency and pioneer in 3D body measurement, in cooperative development with Mayo Clinic, has launched an app to help people measure their BVI.

Here’s how it works: doctors take two photos of their patients, wearing just their underwear, from the front and from the side. After the photos are taken, they are turned into 3D body silhouettes, and sent to a backend server where the images are compared to a database compiled from thousands of MRI images, 3D body scans, and Cadaver information. (The photos themselves are then deleted.)

By cross-referencing 3D silhouettes of patients with this database, the app provides more detailed information on weight distribution and volume, particularly for the abdomen, the area of the body “associated with the greatest risk for metabolic disease and insulin resistance,” said Medina-Inojosa. An increasing body of research suggests that fat in the midsection, which blankets the organs, is associated with a higher likelihood of premature mortality than fat carried in other areas of the body. Two women could be the same weight and height, but if one carries most of the weight in her hips, while the other’s is distributed primarily in the stomach, the latter would be at greater risk of developing a host of health issues. Their BMIs would be identical, but because BVI considers weight distribution and the percentage of fat stored in the abdominal cavity, those numbers would be different.

Not only does BVI serve as a more granular measurement, but Medina-Inojosa believes it can also be used as a tool to improve motivation and accountability; it’s possible to gain muscle and change one’s overall body shape, without seeing a similar shift in BMI.Most importantly, however, he hopes a new system will help people realize that “obesity is a complex disease not only defined by weight.” He’d like to see the conversation move beyond a fixation on pounds gained and lost.

Source: Fortune


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