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


Today’s Comic

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


Today’s Comic

Mediterranean Diet May Ease Chronic Pain of Obesity

Richard Monks wrote . . . . . .

People who are overweight and plagued by chronic pain may find relief in a Mediterranean diet, new research suggests.

The study of 98 men and women between the ages of 20 and 78 builds on growing evidence that a diet heavy on fish, fruits, vegetables, nuts and beans provides significant health benefits. It also sheds new light on why eating these foods might reduce pain associated with obesity.

Because obese people with chronic pain usually also have a high degree of inflammation, lead researcher Charles Emery suspects the foods’ anti-inflammatory properties might explain the reduced pain levels.

“Although the relationship of body fat and pain has been well-documented in prior studies, the mechanism is not known,” said Emery, a professor of psychology at Ohio State University.

“One possibility is the stress of body weight on joints. A second possible mechanism is via inflammatory factors in the bloodstream, because both body fat and pain are known to be associated with elevated inflammation,” he said.

Slightly more than 70 percent of American adults are overweight, with 38 percent considered obese (at least 30 pounds overweight), according to the U.S. Centers for Disease Control and Prevention.

For the study, Emery and his Ohio State colleagues reviewed participants’ eating habits and their answers on a short questionnaire about the pain they experience. The researchers also considered the participants’ age, mental health and use of pain medications.

The upshot: No matter what they weighed, those who ate more fish and plant-based proteins such as nuts and beans had less pain.

While adjusting their findings to account for age-related pain among older participants, the researchers found that a Mediterranean diet benefited men and women of all ages.

Emery said the study had limitations, however: The researchers did not account for chronic pain that lasted more than a month and did not take blood samples to study signs of inflammation. More research is needed to support the initial findings.

Also, only an association was seen between diet and pain, not a cause-and-effect link.

“The next step is to conduct a study with blood markers of inflammation,” Emery said. “Then it would be ideal to conduct an intervention study to evaluate change in body fat, inflammation and pain.”

A nutrition expert who reviewed the study said it reinforces the health benefits of a diet centered on seafood and plant-based proteins.

“This study provides an early look at a possible role diet might play in offsetting pain, but more research is needed,” said Connie Diekman, director of university nutrition at Washington University in St. Louis.

“Studies are needed in healthy adults to see if inflammatory markers are the same with similar pain as they are in obese adults,” she said. “Studies are needed that look at diet over a longer period of time.”

Diekman said it would be beneficial to know, for example, if following a Mediterranean diet while young affected a person’s pain as an adult.

Still, Diekman said the new findings help drive home the point that what you eat matters.

“The bottom line here is that this is an interesting study, it gives us something to think about as we counsel clients — diet might help your pain. But it doesn’t give us a clear answer to whether if you lose weight your pain will go away,” she said. “We need more research to make that connection.”

The study was published recently in the journal Pain.

Source: HealthDay


Today’s Comic

Whole-fat Milk Consumption Associated with Leaner Children, Research Finds

Children who drink whole milk are leaner and have higher vitamin D levels than those who drink low-fat or skim milk, new research suggests.

Children who drank whole (3.25 per cent fat content) milk had a Body Mass Index score that was 0.72 units lower than those who drank 1 or 2 per cent milk in the study published today in the American Journal of Clinical Nutrition.

That’s comparable to the difference between having a healthy weight and being overweight, said lead author Dr. Jonathon Maguire, a pediatrician at St. Michael’s Hospital.

The study did not assess why consuming higher fat content milk was associated with lower BMI scores. But Dr. Maguire hypothesized that children who drank whole milk felt fuller than those who drank the same amount of low-fat or skim milk. If children don’t feel full from drinking milk, they are more likely to eat other foods that are less healthy or higher in calories, said Dr. Maguire. Therefore children who drink lower fat milk may actually consume more calories overall than those who drink whole milk.

The study also found that children who drank one cup of whole milk each day had comparable vitamin D levels to those who drank nearly 3 cups of one per cent milk. This could be because vitamin D is fat soluble, meaning it dissolves in fat rather than water. Milk with higher fat content therefore contains more vitamin D. There may also be an inverse relationship in children between body fat and vitamin D stores, according to the study; as children’s body fat increases, their vitamin D stores decrease.

“Children who drink lower fat milk don’t have less body fat, and they also don’t benefit from the higher vitamin D levels in whole milk,” said Dr. Maguire. “It’s a double negative with low fat milk.”

The study’s findings differ from Health Canada, National Institutes of Health and American Academy of Pediatrics guidelines recommending two servings of low fat (one per cent or two per cent) milk for children over the age of two to reduce the risk of childhood obesity.

Dr. Maguire said the findings indicated a need to closely examine existing nutritional guidelines around milk fat consumption to make sure they are having the desired effect. Childhood obesity has tripled in the past 30 years while consumption of whole milk has halved over the same period.

“What kind of milk our children should be consuming is something we need to seek the right answer for,” said Dr. Maguire.

For this study, researchers studied 2,745 children ages two to six years attending well-child visits. They surveyed parents, measured height and weight to calculate BMI and took blood samples to assess vitamin D levels. All were enrolled in the Applied Research Group for Kids (TARGet Kids!), collaboration between children’s doctors and researchers from St. Michael’s Hospital and The Hospital for Sick Children. The program follows children from birth with the aim of preventing common problems in the early years and understanding their impact on health and disease later in life.

Of those studied, 49 per cent drank whole milk, 35 per cent drank two per cent milk, 12 per cent drank one per cent milk and four per cent drank skim milk. Less than one per cent of children drank some combination of the four types of milk.

Source: Medical News Today


Today’s Comic

Meat Consumption Contributing to Global Obesity

Should we be warning consumers about over-consumption of meat as well as sugar?

That’s the question being raised by a team of researchers from the University of Adelaide, who say meat in the modern diet offers surplus energy, and is contributing to the prevalence of global obesity.

Comparative anatomy and human evolution experts from the University’s School of Medicine have been studying the correlation between meat consumption and obesity rates in 170 countries.

“Our findings are likely to be controversial because they suggest that meat contributes to obesity prevalence worldwide at the same extent as sugar,” says Professor Maciej Henneberg, head of the Biological Anthropology and Comparative Anatomy Research Unit.

“In the analysis of obesity prevalence across 170 countries, we have found that sugar availability in a nation explains 50% of obesity variation while meat availability another 50%. After correcting for differences in nations’ wealth (Gross Domestic Product), calorie consumption, levels of urbanisation and of physical inactivity, which are all major contributors to obesity, sugar availability remained an important factor, contributing independently 13%, while meat contributed another 13% to obesity.

“While we believe it’s important that the public should be alert to the over-consumption of sugar and some fats in their diets, based on our findings we believe meat protein in the human diet is also making a significant contribution to obesity,” Professor Henneberg says.

The research has been conducted by PhD student Wenpeng You, who recently presented the findings of his work at the 18th International Conference on Nutrition and Food Sciences in Zurich, Switzerland. This research has also formed the basis of two papers on the issue, published in BMC Nutrition and the Journal of Nutrition & Food Sciences.

“There is a dogma that fats and carbohydrates, especially fats, are the major factors contributing to obesity,” Mr You says.

“Whether we like it or not, fats and carbohydrates in modern diets are supplying enough energy to meet our daily needs. Because meat protein is digested later than fats and carbohydrates, this makes the energy we receive from protein a surplus, which is then converted and stored as fat in the human body.”

Mr You says there have been several other academic papers showing that meat consumption is related to obesity, but the authors have often argued that it’s the fat content in meat that contributes to the problem. “On the contrary, we believe the protein in meat is directly contributing to obesity,” Mr You says.

Professor Henneberg says: “It would be irresponsible to interpret these findings as meaning that it’s okay to keep eating a diet high in fats and carbohydrates. Clearly, that is not okay, and this is a serious issue for our modern diet and human health.

“Nevertheless, it is important that we show the contribution meat protein is making to obesity so that we can better understand what is happening. In the modern world in which we live, in order to curb obesity it may make sense for dietary guidelines to advise eating less meat, as well as eating less sugar,” he says.

Source: The University of Adelaide