Are you still relying on BMI as the end-all-be-all of health indicators? Let's unravel why it's time to break up with this outdated metric. Join me, Colleen Sloan, on the second episode of this 10-part series to help guide your patients on their weight loss journey.
If you're a primary care provider looking to enhance your nutrition counseling skills or simply seeking a refresher, join me as we make our patients healthier, one exam room at a time!
Grab the companion PDF at examroomnutrition.com/weightloss, and let's confidently guide our patients towards their best lives in 2024.
Resources and Articles:
Obesity Management in Adults - JAMA Review
AMAs new policy clarifying the role of BMI
ConscienHealth Blog - Our Rocky Relationship with BMI
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A person's BMI doesn't matter as much as we once thought. It cannot measure health, but it is a simple screening tool. Now, simple is useful but not comprehensive. I'm Colleen Sloan, registered dietitian and pediatric PA, and this is the Exam Room Nutrition Podcast, where I'm giving you the nutrition education you never had in school to help you become a confident, compassionate clinician. This is the second episode in our series titled A Provider's Guide to Helping Patients Lose Weight, and last week I gave you three crucial questions to ask your patient who wants to lose weight, and this week we are getting into some metrics and how we can measure the patient's outcomes. As a quick reminder, if you would like my notes on this series, I have created a companion PDF for you that summarizes each and every episode. You can find that for free at examrumnutritioncom slash weight loss. That's examrumnutritioncom slash weight loss. Now, before we get into the material for today, I wanted to add that helping patients lose weight should include interventions in all categories, including behavioral interventions, nutrition, physical activity, pharmacotherapy and possibly bariatric procedures. I firmly believe that evidence-based obesity treatment combines all of these interventions. However, I am a registered dietitian, so I'll be providing you guidance only on that which is within my scope of practice. Additionally, if your patient requires more guidance than you can provide, please don't just tell them to eat less and move more. Please refer them to an appropriate professional who can help in the areas that you can't. But for this series, I'm talking to my colleagues in primary care who are faced with the questions of weight loss daily. This information is to equip you with the knowledge to guide your patients appropriately. So let's get into BMI and why there might be better outcomes to measure. Bmi has long been used as a way to classify obesity. Insurance plans use it to determine eligibility for bariatric metabolic surgery, and medical organizations have used it for decades as a determinant of health risk. Now, as a reminder, a BMI of 25 or greater is commonly used to define overweight and a BMI of 30 or greater to define obesity. Bmi does not measure excess adipose tissue or indicate tissue or organ function. It doesn't account for muscle mass or types of body fat and where that's located. But historically it has been an effective measure of estimating the population level magnitude of obesity. But where did we even get BMI from? All right guys? Time for a quick history lesson. It was created by a Belgian astronomer and mathematician, adolf Quettelette in 1832 as the Quettelette Index. The scale was created using data from predominantly European men to measure weight in different populations. Although Quettelette noted that it was a population level tool and not meant to be used on individuals, physiologists Ansel Keys reintroduced the calculation in 1972 as the Body Mass Index, and it has since been adopted by the medical community as a way to measure individual health. But health risks at a given BMI value can be different in different populations, genders and races. This leads some people to make some sensational claims that BMI is racist and sexist. Now, this is a very sensitive and controversial topic that does not suit the goals of my podcast, so we will not be addressing that issue today. Many other studies have shown that BMI cutoffs should be different in different ethnic populations, specifically the Asian populations. But two facts still remain. Number one, bmi is math. Bmi is nothing more or less than a ratio between height and weight as humans age from birth to adulthood. And number two, bmi has limitations. It is a screening tool. It has very real limitations as an individual measure. It does not measure excess body fat, fat distribution, health or fitness levels or account for individual differences in health risks. In a June 14, 2023 press release. The delegates at the annual meeting of the American Medical Association House of Delegates adopted a policy aimed at clarifying how BMI can be used as a measure in medicine. The AMA suggests that it be used in conjunction with other valid measures of risk, such as, but not limited to, measurements of visceral fat, body adiposity index, body composition, relative fat mass, waist circumference and genetic or metabolic factors. So if we shouldn't rely on BMI alone, what should we measure Now? At minimum, you should be screening for a secondary cause of obesity based on history and physical exam. So, for example, check for hormonal abnormalities, any psychiatric disorders and genetic syndromes. In addition to any medication side effects, weight-related comorbidities should be assessed as well. I want you to be thinking non-alcoholic, fatty liver disease, sleep apnea, prediabetes, diabetes, hypertension or reflux. It is critical that you pay attention to muscle mass and body composition, as protecting lean muscle mass should be a priority when working with individuals trying to lose weight. Okay, but what about measuring body composition First? What even is body composition Now? Basically, measuring body composition is just assessing the proportions of your body, in which there are four main components fat, muscle, bone and water. Other components do contribute to weight, such as fluid and minerals. But we're trying to keep it simple today. Now let's discuss the most common ways of measuring body composition and their limitations. So the first way we have is hydrostatic weighing, and this is underwater weighing. This technique involves measuring your weight on dry land, followed by measuring it in water. To measure your weight in water, the patient will be seated undressed on a chair that is halfway submerged in water. According to the American College of Sports Medicine, this is the gold standard for calculating body fat because of its high accuracy. However, it is very time consuming and is probably not available everywhere. Usually, this type of measurement is only available at D1 universities. Number two is a BOD pod. This is testing that uses the principle of air displacement. During the test, the patient is enclosed in a computerized egg-shaped chamber called a BOD pod. Before the patient enters the chamber, body weight and volume measurements are taken. Then, when you're in the chamber, the body fat percentage is calculated by measuring the amount of air your body displaces upon entering. The BOD pod test is highly accurate and gives fast results. However, it needs technical expertise and it can be very expensive. Furthermore, I'm told that you have to wear a skin tight suit and that might not be comfortable or acceptable for all patients. The third way that we can measure body composition and you're probably very familiar with it is the DEXA scan, and most of us know this as a way of measuring bone density. However, it can also provide measurements of body composition, including muscle, bone and fat content in specific parts of your body. The scan generates a fat shadow image that shows the distribution of fat in the abdomen, arms, legs and pelvis. The DEXA scan does provide fast results. However, the machine is only available in some hospitals and research institutions, where it's typically reserved for research studies and not always for the general public use. The next way we can measure it is the Bioimpedance Analysis, or BIA. This test works on the principle that water and fat conduct electric currents differently. During the test, a small, harmless electric current is passed through the body and the speed at which the current travels helps detect the amount of body fat. If the current travels slowly, this usually indicates a higher body fat percentage. You can think of it like this the current will travel faster through water and muscle and slower through fat. Different machines will offer different measurements, but in general, most can tell you your muscle mass, your body fat, visceral tissue and body water composition. Some fitness centers actually have this, so this might be a really good option for patients, and it's becoming more and more acceptable as a great way for body composition measurement within clinics. Another option is the skin fold test. This test requires a special scale, called a Vernier caliper, to measure the thickness of various skin folds in the body. Thanks to the simplicity and low cost of Vernier calipers, the skin fold test is widely used to measure body fat. However, this method is not very accurate because it depends on how precisely the measurements are taken. Repeated measurements made by different people may not provide accurate results. Furthermore, it only measures subcutaneous fat. It's not measuring the fat that's around the organs, which is the more concerning dangerous fat, and honestly, this isn't very patient-friendly because nobody really wants their arm fat and waist fat pinched and measured. Another method available is the waist to hip ratio. This is a simple measurement of the circumference of an individual's waist compared to that of the hips. Now, there are guidelines for measurements, but there is no uniformly accepted protocol. The measurement is taken with the patient standing up straight and they need to breathe out. Use a tape measure to measure midway between the lower rib and the iliac crest on the mid-accelery line. Often, this is the smallest part of your patient's waist, just above their belly button. This is their waist circumference. Next, measure the distance around the largest part of their hips or the widest part of their buttocks over the greater trochanters. This is the hip circumference. Calculate the weight to hip ratio by dividing the waist circumference by the hip circumference. The World Health Organization defines abdominal obesity as 0.9 or less in men and 0.85 or less for women. In both men and women, a waist to hip ratio of 1 or higher increases the risk of heart disease and other conditions that are linked to being overweight. As with any body composition measurement, there are limitations. Certain people won't be able to get an accurate measure using waist to hip ratio, including people who are shorter than 5 feet tall and people who have a BMI of 35 or higher, and this is not recommended for use in children. It's also really easy to make mistakes while checking the waist to hip ratio, because you need to take two separate measurements and it can be hard to get an accurate measurement of the hips. It also cannot distinguish between subcutaneous and visceral abdominal fat. Additionally, some patients might not be comfortable with this type of measurement. And lastly, a whole body MRI is actually a gold standard to measure skeletal muscle mass and visceral muscle tissue. However, a whole body MRI is often not feasible and it is very expensive. As you can see, each method of measuring body composition comes with its own strengths and weaknesses. These are, at best, estimated guesses, due to each of them having their own amount of error margin. This is why it's important to consider multiple factors when it comes to monitoring your patient's success. So now you know why BMI doesn't tell the whole story about your patient's health and that it's not the only metric you should be monitoring. I want you to consider what is the most feasible for your patient. You need to consider cost, accessibility and patient comfort, okay, but what should you monitor in a patient who is working towards weight loss? This is where a shared decision model is ideal. Ask the patient what can we track beyond your weight? How would you like to measure your success? Successful weight loss treatment involves every part of the person, so ask them what's important to you? I want to leave you guys with something to think about Now. I firmly believe that someone with excess weight can be perfectly healthy, and likewise, someone with a normal body weight can be completely unhealthy. But what is our definition of healthy? How do we measure health in 2024? Is it lab values, like cholesterol and A1C? Is it their mental health, like confidence, self-esteem and stress levels? Is it physical health, like stamina and strength? Is it body fat distribution? What about quality of sleep? Or maybe is it their digestive health? I'm curious to know what you think and how we should be measuring health in 2024. Join the conversation on Instagram and tag me at Exam Room Nutrition. Well, that's it for today, guys. I'll see you next week where we talk about the psychological factors you cannot ignore and how helping your patient be aware of and manage their stress and emotional eating will be key to their success on this journey. As always, let's continue to make our patients healthier, one exam room at a time. And as a quick reminder, if you would like my notes on this series, I have created a companion PDF for you that summarizes each and every episode. You can find that for free at exam room. Nutritioncom slash weight loss. That's exam room. Nutritioncom slash weight loss.