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Physical therapist and certified lymphedema specialist Maureen McBeth discusses her article “Beyond BMI: Why weight management must look inside the body.” Maureen explains why common tools like the bathroom scale and body mass index can misclassify up to 34 percent of the general population as obese while masking dangerous internal realities. Drawing from over 25 years in oncology rehabilitation and her own personal experience taking a GLP-1 medication after major surgery, Maureen warns that rapid weight loss can lead to severe muscle depletion and malnutrition if not properly monitored. She highlights the critical importance of tracking three core components of health: muscle mass, intracellular water, and balanced extracellular water. By utilizing noninvasive bioimpedance spectroscopy assessments, clinicians can provide actionable insights to protect a patient’s structural and metabolic foundation during their weight loss journey. Discover how looking beyond the scale can transform your approach to long-term health and resilience.

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Transcript

Kevin Pho: Welcome to the show. Subscribe at KevinMD.com/podcast. Today we welcome Maureen McBeth. She is a physical therapist and certified lymphedema specialist. Today’s KevinMD article is “Beyond BMI: why weight management must look inside the body.” Maureen, welcome to the show.

Maureen McBeth: Kevin, thank you for having me. This is something I am really passionate about talking about.

Kevin Pho: All right, so your article is “Beyond BMI: why weight management must look inside the body.” What led you to write this article, and then talk about the article itself for those that didn’t get a chance to read it?

Maureen McBeth: Sure, Kevin. It was really personal for me. Last year I unfortunately had to have a big surgery. I had a pre-melanoma, actually it was melanoma in situ. For those of you who don’t know, it is like early-stage melanoma, but it is a really deadly disease, and it was right on my nose. I had to have a paramedian forehead flap, so the makeup kind of covers it. I had a good plastic surgeon, but I had major facial reconstruction surgery. With that, I could do nothing for about three months and I gained a lot of weight. Admittedly, as a postmenopausal woman, this is tough. Like I am a physical therapist, I should know how to take care of my body and how to lose weight, and I was struggling.

So I finally talked to my doctor and went on a GLP-1. It wasn’t without a lot of consideration because I have been in the PT space for over 30 years and I have been using bioimpedance spectroscopy. That is what I work with at a company that uses that as a technology for lymphedema and for body comp. I was scared because of the results. I saw people I had tested and their body comp, really their metabolic engine, had been destroyed.

Kevin Pho: So what does that mean? When you are seeing these people on GLP-1s, they lose a significant amount of weight but you see their body composition has been destroyed. What does that look like from your standpoint as a physical therapist?

Maureen McBeth: Yes, as a physical therapist, I have been studying equipment. I had a research device in 2007 for this bioimpedance spectroscopy. It is a very accurate way of measuring fluid in the body and we can get tissue outputs. So I started looking at this years ago and noticed women going through breast cancer who had a normal BMI but had really elevated body fat.

Fast forward to 2017, I had this fancy stand-on device and again started testing every one of my patients on it. Over that time, GLP-1s became more prevalent and I had people coming in saying they were on it. They wouldn’t actually tell me at first. That is part of the problem. The stigma of being on a GLP-1 meant people didn’t want to tell you.

But I would see these body comp results and I would think: “Huh, you have lost 50 pounds and your scale weight is looking great. But I put you on body composition testing and you have really low skeletal muscle mass. You have exceptionally high body fat, and it is not making sense.” So I started going back and looking at more and more patients, and this was a trend that we saw. Then I got involved professionally with some of the organizations looking at body composition across all areas of patients in medicine and did the research. We said we know that people on these GLP-1s are losing muscle mass. They are losing weight way too fast, and then all that is left is kind of a depleted body.

My concern going on one was that I sort of had a bias. As clinicians, we all develop these cognitive biases because we have seen too many things. My doctor was kind of pressuring me and asked why I didn’t want to go on a GLP-1. I said it was because I was scared to. I had seen too many people lose their metabolic engine. I like to call it their muscle. That is already happening as we age as we know it. So I wanted to really make sure.

I actually put it to the test and sort of did a case study of one on myself. My goal was to make sure, and this is what I talk about in the article, that we as medical practitioners have an opportunity to make sure that this whole GLP-1 thing goes in the right direction. We have got to really push to make sure that patients are getting tested for their body composition before they start these drugs. We need to ensure that they are monitored throughout and that we don’t let them lose weight too fast or not exercise or not eat the right way. With drugs, people want a magic easy button.

Kevin Pho: So from the perspective of a physical therapist, people going on GLP-1 agonists lose a lot of absolute weight, but it sounds like the weight that they are losing is primarily in the form of muscle. Now, from the perspective of a physical therapist, why is that so dangerous, losing so much disproportionate muscle mass?

Maureen McBeth: It is really dangerous because we know that it is that muscle that is really driving our health. A lot of the data, again, I am biased towards the cancer space, shows how important exercise is for people going through cancer. So if they aren’t moving, if they aren’t exercising, and if the exercise isn’t being dosed, they are not going to actually preserve their muscle.

Preserving muscle really sort of takes two inputs. It takes dietary inputs and we have to use our muscles. I mean, disuse atrophy used to be a really big problem in PT because there were so many conditions where we just said you have got to rest. Well, that is not true anymore. If people are going through cancer treatment or even thinking about orthopedic injuries, we get people moving now. As a physical therapist, it is my job to make sure I dose exercise correctly. We can’t let people lift two-pound weights because that doesn’t do the trick. So while total physical activity is super beneficial to people, we actually need to make sure we are lifting the right amount of weight and that people have the proper dietary input.

I also consulted a dietitian for my journey, and that was really important because a lot of people don’t realize when they go on these drugs that you are not really interested in eating. I mean, you still enjoy eating. Trust me, I still love a really good meal. But you don’t have that drive like you did before, and that is some of that gut-brain axis thing that is changing.

The problem with that is if you are not getting the proper nutrition, they have study after study showing people go into a caloric deficit that is too great to maintain. They are going below what their body needs on a daily basis. For example, my dietitian set my goal at 1500 calories a day and I would still lose steady, slow weight, but my bottom was 1200. I really struggled because I tracked and trended this. I actually have this book that I used as a paper journal. It was more helpful than an app and it really made me just write things down to make sure I was getting those protein macros and the calories each day.

I found after two weeks I had already dropped from close to 1500 down to like 1238. That got me thinking that if people aren’t really tracking and trending this, they are not going to know. About three to five months in, I had an instance where I had decreased the amount of time I was using the bioimpedance device that I have. I started to pick up a little fat mass again and my skeletal muscle mass started to dip. It took me about a month to correct that, and again, the biggest problem is the diet and people not being able to manage that. That is where the article comes in, and I have really tried to use my own personal situation to get the conversation going.

Kevin Pho: So many people just step on a scale or use body mass index to track how much weight they have lost on a GLP-1. Are you recommending that they also check their body fat index and their muscle mass percentage along with absolute weight?

Maureen McBeth: Absolutely. Actually, it is not just me saying that, but all the organizations that are trying to set guidelines for this are all now recommending that you use some other form of body composition testing. BMI is not adequate and the scale could actually be almost dangerous. Again, a lot of the weight that people lose in the beginning is actually water weight.

So it is sort of amazing to be able to track that. Regarding the technology, I am a senior medical affairs liaison. So I am the nerd behind what my company does, so I get to read all the research and everything. A lot of people don’t realize it in the beginning that a lot of early weight loss is fluid loss. You need to track that too. You have got to make sure you are taking enough fluid in and then you have got to really get everything fine-tuned.

I always think about three things. The patient has to understand that their body fluctuates too, and fluid fluctuates. This is also why the scale can really freak people out. They get on the scale in the morning, they get on at night, and they think they gained two pounds. They think they have got to do something, so they stop eating the next day. That is the worst thing they could do. Or they stop drinking that extra glass of water.

That is where the tracking becomes really critically important. I don’t even think we really know the optimal timeframes, like whether we should be tracking once a week, every other week, or once a month. I think that is what the research right now is really trying to figure out in this space.

Kevin Pho: So in terms of the listeners on GLP-1s listening to you now who want to track some of the body fat index and muscle mass, how can you do that? Can you just go on Amazon and know they sell all these things on Amazon? Is that good enough? What would you recommend?

Maureen McBeth: That is good for tracking and trending. A home device can be good, but I really feel like it is incumbent upon the medical profession. If we are prescribing these very powerful weight loss medications, we should be matching it with tests. We don’t prescribe a drug and then not do blood work, for example. We have got to match our treatment with our ability to actually understand critically what is happening with the patient.

Again, that is why I have looked for opportunities like with you to really get the word out to people. You saw the Super Bowl and you saw all the ads for GLP-1s. You probably heard already that I think a certain company got an FDA letter this week. That is big news because there is a huge amount of money behind this. There is a lot riding on it. There are a lot of issues with our entire public health about this.

As a medical community, we have got to take that responsibility. That is why I have been trying to go public and say I know how scared I was as a health care provider to even go on this medication. This has transformed my life. I don’t know where I would be without this. I mean, I have lost 26 pounds since last June, and I have been able to preserve my muscle mass because I have been tracking and trending that. It is really exciting, but it has also just had other downstream benefits that this podcast isn’t long enough to talk about.

I think this is a medication we should be using, but we have got to be really wise about it. Again, I know I am preaching to the choir here, but we have got to get the rest of our colleagues to recognize how important it is if we are going to use this. We need to reduce the stigma and track and trend these patients. Make sure we are using proper objective measurements. That also includes, as a PT, strength and functional outcome measurements as well.

Kevin Pho: So tell us for those on GLP-1s exactly what kind of exercise they should be doing and how much they should be lifting to preserve that muscle mass during the weight loss journey.

Maureen McBeth: That is a tough question to answer because it is quite personalized. We are starting to recognize the exercise prescription. There is something called a one-rep max. If you don’t know how to figure that out, you need to see a professional. So whether that is an exercise physiologist, a professional trainer, or a physical therapist, if you are very exercise naive, you should probably be asking your doctor for a prescription to go to a PT or an exercise physiologist who can help with this. They have to see where you are at right now.

The good thing is we have a lot of age-related norms, things like grip strength, and there are some other easy tests that even doctors can learn to do in their own office, like a sit-to-stand test. You can really find out if someone is below where they should be for their age. If they are, that is someone who really needs professional counseling versus someone who could likely go to the local gym and hire a trainer.

But slow and steady wins the race. The first week you start, you can’t start off hard. There are a lot of adaptive benefits just from starting to get into regular exercise. We do know the American College of Sports Medicine has got recommendations for the average person that they can start to do. It is really two to three times a week. These exercise sessions need to be enough to stress your body.

Probably the word I want everyone to look up is myokines. If you don’t know what myokines are, it will be one of these moments where you are amazed. These are all the signaling things that actually come from our muscles, and these are what drive all the wonderful adaptive and protective benefits of exercise. We have got to be able to stimulate those enough. I hope that answered that question.

Kevin Pho: Now what about those patients who are listening to you and saying they have already lost so much weight, but their body fat composition is higher than it should be? Is there any way to reverse the cascade of muscle loss once it begins during a GLP-1 journey?

Maureen McBeth: That is another great question because they are trying to figure that out. I think a lot of people know there is never a bad time to start exercising. So if you are on a GLP-1 and you are not doing any extra physical activity, then you need to talk to your doctor about that. Whoever is prescribing it, tell them you need to know more about this. It is never too late to start. We have done exercise studies in people in their eighties and nineties, and they can reverse some of these changes. You may not be able to grow big, giant muscles, but you really can do something at any point. So it is never too late to start.

The key is trying to recognize that you can’t just let the drug do the work. If you just let the drug try to do the work, you are going to run into these problems.

Kevin Pho: Now, what about those other physicians who are listening to this? I prescribe my fair share of GLP-1s. In addition to exercise during that journey, is there anything else that we need to counsel patients about that we may not know about that you have experience with? What are some other things patients should know about?

Maureen McBeth: I think that the side effects and monitoring those can be important. There are a lot of common side effects. People will talk about that feeling of fullness or dyspepsia, like indigestion. I think they just have to make sure they monitor it. I would love to see better tracking methods that people can just honestly say to you how they are experiencing things this week. I actually used a book. I modified a book that a colleague had made for other conditions and it was really nice because it had an opportunity for me to say how I was feeling that day. How is my function? Am I still able to do all the things I want to do? Am I having any other disruptions with sleep or something else?

Because again, I think for me it has made me more perceptive about my own issues and a better communicator back to my physician. I think that is what we are trying to do is develop that communication. I remember reading something that you wrote stating that we shouldn’t be gatekeepers anymore. We really should be an active partner and help our patients find the best path forward. That is really what I feel like I am trying to do, which is open up that conversation.

I will just say I knew no one on a GLP-1. None of my colleagues would admit to me they were on a GLP-1 until I came forward with it publicly. Now all of a sudden, I know probably 30 people that are on GLP-1s. Make sure your doctor knows if you are getting this on the side. Don’t do it that way. Make sure the conversation is with your physician because it is really important. Then again, what physicians can do is make sure the patient has an opportunity to track and trend their body comp. Make sure they have an opportunity to exercise. If they need a dietitian, they need the professionals.

Kevin Pho: We are talking to Maureen McBeth, physical therapist and certified lymphedema specialist. Today’s KevinMD article is “Beyond BMI: why weight management must look inside the body.” Maureen, let’s end with take-home messages that you want to leave with the KevinMD audience.

Maureen McBeth: The take-home message is that GLP-1s are a phenomenal tool. We should be embracing them, but we should be embracing them with the guardrails that we need for safety, for efficacy, and to make sure that patients’ lives really can be transformed with them.

Kevin Pho: Maureen, thank you so much for sharing your perspective and insight. Thanks again for coming on the show.

Maureen McBeth: Thanks again.