For many years, doctors and other scientists have been measuring the amount of fat in a person’s body using something called the Body Mass Index.
But what if that method of measurement is less than accurate? It could impact how much useful health information people have, which could lead to unintended consequences.
“We know that BMI varies according to age, ethnicity and activity level,” said Olivia Affuso of the UAB School of Public Health. “Older individuals tend to lose muscle mass with age, which could result in a normal BMI, but a significant amount of body fat. Whites tend to have greater body fat than blacks at the same BMI. And individuals who exercise tend to have less body fat than non-exercisers at the same BMI.”
For example, compare an athlete to a non-athlete. The BMI issue becomes clear. “Although two individuals may have the same height and weight and thus the same BMI, they may have different amounts of body fat,” she said. “For example, compare an average Joe American to a professional body builder. There would be differences in body fatness that would be readily apparent to anyone. So, it is easy to see how using BMI could make it difficult to establish true relationships between obesity and health outcomes if BMI is used.”
So, what does this mean?
For one thing, Affuso said, it means people may not trust their BMI. “I think that individuals tend to discount their BMI values even if reported to them by a healthcare professional. So, if a doctor says to her patient that their BMI is greater than 24.9 (i.e. overweight) or [greater than] 29.9 (i.e. obese) and recommends that the patient change their lifestyle to reduce their weight, the patient may not take the information seriously until they experience serious health problems such as a stroke or heart attack.”
Affuso and a team of UAB researchers are trying to find a better way to tell how much fat is actually in a person’s body, using a technique older than the BMI: photography. Affuso is the principal investigator in the Photobody Study, working toward a photographic method of measuring human body composition, which could provide useful information in looking at how excess body fat can lead over time to health issues.
Affuso talked with Weld about the study, which is seeking participants.
Weld: What are the parameters of the study?
Olivia Affuso: For this study we are attempting to enroll 2,160 individuals, and as of today we have enrolled 1,300 men, women and children of all shapes and sizes. The study requires one one-hour visit to the Photobody Lab located in the Ryals School of Public Health.
Weld: What are the potential benefits to finding another way of measuring body composition?
OA: One of the major benefits of our new method for measuring body composition is that it is easy, portable, inexpensive but, most of all, it performs better than body mass index (BMI), which has been shown to misclassify obesity levels in both clinical practice and research studies.
Weld: Has anyone done a study like this before? If so, when and where, and what were the outcomes?
OA: To our knowledge, this is the first study to use two simple pictures from a digital camera to estimate body fatness from a 3D model of body volume. Our work is based upon experiments dating back to the 1930s where photographs were used to estimate body volume as well as visual ratings of body fatness by human observers. However, improvements in technology allow us to integrate and automate the process of volume estimation and body fat prediction.
Weld: How did this question end up at UAB?
OA: My colleagues, David B. Allison, Ph.D., Chengcui Zhang, Ph.D., and I developed this idea about 6 years ago through our joint interests in obesity and computer image analysis. My experiences with lab-based body composition assessments and the need for an accurate but practical method for measuring obesity in large groups of study participants helped to formulate this question. We have a patent pending.
Weld: What is your special area of expertise?
OA: I am an epidemiologist with training in nutrition and exercise science; Ph.D. from the University of North Carolina at Chapel Hill and postdoctoral fellowship at the University of Miami.
Weld: What will the volunteers in the study have to do?
OA: Participants will have their height and weight measured, have 3 photographs taken (front, side and back profile) while wearing close-fitting cycling shorts and tank top (females only) that we provide and have a total body scan (DXA — or dual energy X-ray absorptiometry, which uses low level X-rays to measure fat, muscle and bone) for body composition assessment.
Weld: What will they get out of it?
OA: Participants will receive their study results immediately as well as a $20 incentive for their time.
Weld: What do you hope to ultimately accomplish?
OA: At the completion of this study, our goal is to have software that clinician and researchers can use with any simple digital camera to accurately measure body composition in their patients or study participants.
Weld: How do people reach out to participate in the study?
OA: We are specifically looking for males and females in the age groups of 6-20 and 41-70. Interested individuals should contact our study recruiter, Billy Tingle at billy@uab.edu, to be screened for study eligibility.