In this episode, Dr. Scott and Tommy discuss the often cited concern of metabolism and how weight loss and diets can affect resting metabolic rate. Adaptive thermogenesis is one of the body's homeostatic responses to changing caloric intake, which can lead to a change in metabolic rate. They discuss how these relate to fasting and how to use this information to optimize fasting results and support long-term metabolic health.
Nunes CL, Casanova N, Francisco R, et al. Does adaptive thermogenesis occur after weight loss in adults? A systematic review [published online ahead of print, 2021 Mar 25]. Br J Nutr. 2021;1-19. doi:10.1017/S0007114521001094
Is it true that weight loss can result in a “slow metabolism”?
Fasting For Life Ep. 86
Dr. Scott Watier: [00:00:01] Hello, I'm Dr. Scott Watier,
Tommy Welling: [00:00:03] And I'm Tommy Welling, and you're listening to the Fasting for Life podcast, and
Dr. Scott Watier: [00:00:08] This podcast is about using fasting as a tool to regain your health, achieve ultimate wellness and live the life you truly deserve.
Tommy Welling: [00:00:15] Each episode is a short conversation on a single topic with immediate, actionable steps. We cover everything from fat loss on health and wellness to the science of lifestyle design.
Dr. Scott Watier: [00:00:25] We started fasting for life because of how fasting has transformed our lives, and we hope to share the tools that we have learned
[00:00:30] Along the way.
Dr. Scott Watier: [00:00:40] Hey, everyone, welcome to the Fasting for Life podcast. My name is Dr. Scott Watier, and I'm here, as always, am a good friend and colleague, Tommy Welling. Good afternoon to you, sir.
Tommy Welling: [00:00:48] Hey, Scott. How are you
Dr. Scott Watier: [00:00:49] Doing? Great. My friend going to have a good conversation today. And I'm hoping, as always, that it'll be actionable and enlightening for all of your listeners. So just I don't really know where today is going to go. Full transparency. We've we've talked around these conversations pretty much week in and week out in our groups and underlying challenges and communications back and forth with you guys. And one of the things that I love about the conversation today is it's going to be around one of the main topics as to why people come to fasting. So we're going to talk about weight loss, but we're also going to talk a little bit about the mythical creature called metabolism and talk through some of what we feel leads to fasting as being a beneficial way to get the best of both worlds. When you are living in an insulin friendly or fasting friendly lifestyle compared to the calorie counting, macro counting, low and slow calorie restriction world. So not really sure. Like I said, tell me where it's going to go. I know you and I each have our thought processes on this, but I'm excited to have the conversation because there's a couple of cool takeaways at the end that I think are going to put a nice kind of bow on things and then they'll be, as always, an action step that we can put in to level up our fasting game, which is ultimately getting the results of long term weight loss and health benefit.
Tommy Welling: [00:02:24] Yeah, absolutely. And that that mythical word, that metabolism, we each have our our histories with that word. And I think just the idea of slowing my own metabolism or, you know, just kind of the fear and the hesitation around it is is is kind of what kept me from actually discovering fasting much sooner, much earlier in my journey. But I didn't want to do that. And I knew I had heard that before. And, you know, there's there's just a lot of a lot of misunderstandings and a lot of claims out there regarding metabolism. And so it can be kind of a frustrating, uncertain thing to kind of navigate.
Dr. Scott Watier: [00:03:09] Yeah, so with metabolism, two things, the article that we are going to discuss is and this came from a summary of the actual research article and the summary was to be enlightening or to catch your eye. It says, is it true that weight loss can result in a slow metabolism? Right. And. One of the things that's out there that you hear a lot or you can you can hear or see in your in your circles of friends and family, co-workers, is the law that someone has a fast metabolism is someone that has a high resting metabolic rate. Him or her can eat an infinite amount of food with any without any fat gain. But that's not absolutely true. So going past the growth years. Right. So when we're growing and developing as kids and young adults as an adult, once you get past that, these such these these unicorns don't exist. Some adults do have slightly higher armoires or resting metabolic rates than other people, but the entire individual variations tend to stay within about two to three hundred kilo cows per day. So people that typically have higher caloric needs, which is that higher resting metabolic rate, tend to compensate by eating more. So that one's natural. That person's natural rest of Welling resting metabolic rate is then a poor predictor of weight gain over over the long term. So with that being said, the reason I like that the the summary that caught my eye on him losing weight cause a slow metabolism. This study looked at it was a systemic review and it was out of the British Journal of Nutrition and twenty twenty one. And it talks about a term called adaptive thermogenesis. So that the actual article is called Does Adaptive Thermogenesis Occur After Weight Loss in Adults? And this is a systemic review. So this looks at a bunch of different studies and then comes with comes up with a couple of Take-Home messages, which we're going to reinforce by some studies on actual fasting windows that we use a lot, meaning the timing anywhere from 18 all the way up to forty eight, sometimes seventy two hours.
Tommy Welling: [00:05:39] Yeah. And you know, just to be clear, I wanted to kind of define adaptive thermogenesis, that process being basically the the compensation that the body can can go through can actually adapt to burning calories and burning energy at a different rate, especially when we go through a period of change in our actual input. So reducing or increasing our calories that we have coming in and then the body has different mechanisms to do what it loves to do, which is maintain homeostasis. So the body doesn't like to change it much prefers to stay comfortable, continue doing what it's been doing. That's much easier. It gets a very efficient at doing that. And so in it has different levers to pull to actually change metabolic rate and thermogenesis given different levels of input.
Dr. Scott Watier: [00:06:38] So one thing, if you are in this space and you're familiar with things like adaptive thermogenesis and Southsea and RMR in any 80s, all of these different categories of what your body does with the food energy that you bring in, then the article probably isn't going to have a big aha moment for you. But there's a couple of connection points or nuance things here telling me that you and I really like about it. And the one is that adaptive thermogenesis. One of the main takeaways from the study is that it's probably not statistically relevant for most people. And but it does take into account that adaptive thermogenesis typically, not typically it has involves interactions between other hormones that we see improve when forecasting things like the hormones, leptin and ghrelin, which are the two that tell your body to that you're hungry or that your full insulin, thyroid hormone, stress hormones like cortisol, norepinephrine, epinephrine. So when we're looking at. This, the systemic review of the thirty three studies, it was it was saying that adaptive thermogenesis is a potential problem for the maintenance component, like meaning when you get to your ideal weight or in the process of hitting the plateaus to get to your ideal weight, adaptive thermogenesis can be one of the major roadblocks because as your body body down regulates its energy, it being burned off through a T, you you eventually need less when you get to your end goal. But we want to make sure that we're not inducing this 80, which is going to cause us to never get to that end goal, if that makes sense.
Tommy Welling: [00:08:25] Yeah, yeah. I think it it does. And I think that's an important point as well, that that's oftentimes misunderstood or not talked about, which is the fact that when, you know, if you go through a substantial weight loss phase, let's say let's say you lose 30 pounds, let alone more than that. But even if you lose 30 pounds, that can be a 10 or 15 percent reduction in how many overall calories you're going to be burning on a day to day basis. So that means going through that transition, you're going to be slowly needing fewer and fewer calories as you go through. And if if your weight loss is even greater than that, then then the difference is going to be even more substantial than that, too. And I think that just knowing that going forward means that if I eat the exact same things that I did, even just to maintain my old higher weight, then I will be storing those extra calories as long term fat deposits even after I reached my maintenance goal. So just understanding that I'm going to need to ingest a little bit less when I get to that. The end goal is is an important consideration.
Dr. Scott Watier: [00:09:34] And this is one of the things that it took me going through my mind, powerlifting, Olympic lifting days and, you know, just consuming, consistently trying to get bigger, get bulkier, move more weight, those types of things. Then I would try to lose weight after the
Tommy Welling: [00:09:52] Like, bulking.
Dr. Scott Watier: [00:09:54] Yeah. Four to six years of doing that where I was like, OK, I don't feel good. My joints hurt, my blood pressure is rising in my mid twenties. This something doesn't seem right here. So then I tried to lose the weight and I didn't learn this until a couple of years down the road when I really got into the nutritional side of things and then eventually went back to get my doctorate and go through the the program and get opened my clinic and all that kind of stuff. It was before then when I didn't realize that when you set your macros and your restriction, if you're following the calorie tracking model, that you should be using your goal weight to set those as your as your restriction. So I always had this problem of like, I need to exercise to burn off more calories and then and then, OK, then I'm going to follow the dietary adherence portion. Right. Like, I'm going to stick to it Monday through Saturday and then I'm going to have my my cheat meal or my my my reward on Sunday. And then then I'll make sure to stick to my consistent exercise, you know, burn those calories and stay moving and make sure I'm focusing on sleep, which back then really wasn't a consideration for me. So what I liked about this article is that that point that you just made, which is you are going to need less if you've got some substantial weight to lose like 20, 30, 40, 50 pounds.
Dr. Scott Watier: [00:11:10] Yeah, your body doesn't require the same energy needs as a metabolic rate, for example, when you get there. So one of the things about 80 or adaptive thermogenesis was which caught my attention, was that it may play a role in the the situation that we never want to happen, which is you gain the weight back, right. You put all that time, effort and energy of getting into a slight caloric restriction and putting all of ramping up the willpower. And then you go through and then eventually you fall off the air quotes, dietary diet portion of your plan, and then the exercise kind of wanes and waxes based on your your life experiences through that time. And the cool thing is, is knowing that 80 may play a role in that, I want to make sure that we land the plane on how we can talk about a couple of things that we can do to avoid this actually being a problem and making sure that when we do get to that and rate that end goal, that our metabolism is healthy, our relationship with food is healthy, and that we're going to be able to maintain those results and not give it all back.
Tommy Welling: [00:12:35] Yeah, and I think that that's that's a really important consideration of kind of beginning with the end in mind. Like we like to say and, you know, so understanding that you're going to need a little a little bit less calories at the end goal is is an important first step, I think, because I think that even that need right there is sometimes mis categorized as a slower metabolic rate. And so if you if you reached a maintenance goal or you had a significant weight loss and then you figured out, you know what, I have I need less calories. Now, not attributing that to a slower metabolism, I think is an important first step to kind of protect your psychology that this was still a win. You got there the right way, even if you have a little bit of a lower caloric need. But further to your point there, that protecting and and enhancing your metabolism throughout the process is a really important point as well. And, you know, that's that's where fasting really can come in, because the basic science of fasting, one of the first things that we started to talk about on the podcast and what helped us kind of get past those initial hurdles of even trying fasting early in the journey was those initial boost in metabolic rate that we see during certain fasting intervals. Right.
Dr. Scott Watier: [00:14:00] Yeah, and the study comes right out and says, furthermore, you know, this concern of adaptive thermogenesis or your body down regulating the metabolism, right? So now it's slower or it doesn't have the same ability to burn off the same amount of food. Well, one, we already kind of just talk through that. You're going to need less when you get there. But the effect of this seems to be attenuated or nonexistent after periods of weight stabilization or neutral energy balance. And this is where I like where you were just alluding to where fasting comes into play. So interspersing periods of energy restriction with periods of energy balance or something as simple as just walking more can mitigate these small potential problems when it comes to this air quotes slowing of the metabolism. So specifically, Tommy, I think you're referring to that study that was looking at the thirty six hour fasting mark when we see an actual increase in our metabolic rate and then all the way up to about seventy two hours and seventy two hours, it doesn't really seem to change any further than that. Yeah. And the other study was I'll just give them both to you and then we can unpack it a little bit. And I think this is what you were alluding to was the one that where the adrenaline was found to be increased at seventy two hours, but not thirty six.
Dr. Scott Watier: [00:15:26] But when adrenaline was measured at forty eight hours, it seemed to induce a larger production of heat, which is thermogenesis. So one of the things that we see with our fast cycling methods that we use is and how I lost all the way back in the day. If you want to hear it, go back and search for the podcast or go back and listen to the original couple episodes is we use these these cycles of fasting anywhere between 18 all the way up to about 72 hours. The majority of them fall in that twenty two to thirty six hour range, which is where we see the increase in metabolic rate counteracting the concern that this article was mentioning about slowing the metabolism due to adaptive thermogenesis. And then furthermore, at forty eight hours, we see an actual increase in that to help your body balance. And that's one of the things. And one of the biggest takeaways for me is, you know, there are ways to directly stimulate adaptive thermogenesis and that's consistent exercise, aerobic activity. So if you're if you don't exercise at all, simply adding walking in could be a key component to getting the scale moving and in kind of fitting fasting into how can I make sure that I'm not doing anything to hurt myself long term.
Tommy Welling: [00:16:44] Yeah, and I like to to visualize this as if if the body likes to stay comfortable, if it likes homeostasis, it it likes it can easily tell when we just go, OK, let's do maybe a five hundred calorie deficit. Right. For example, in and over a week that should be in theory about burning about a pound of fat each week, but reducing our caloric intake by a set amount every single day. And we do the same thing. That's what we call low and slow, just that kind of eat less, move more low and slow. That's the easiest thing for the body to adapt to because it gets really, really predictable really quickly. And it doesn't take long for the body to just shut down a little bit of hormone production, just kind of turn the thermostat down a little bit and and decrease output. And it's really easy to kind of balance that out. Whereas when we're doing fasting, it's it's much more on off. It's more dramatic and it's less predictable for the body to just go. I know what you're about to do now and I can adapt to it. So you can't really do that the same way because it's it's just much more black or white on or off. And so using like, let's say a thirty six hour fast and we see this metabolic boost, we see a little bit more adrenaline, a little more growth hormone, all of these things coming up and and these things are metabolically protective. And then we get a little bit more time to increase insulin sensitivity and burn through some of those long term fat stores. Like now we're looking at at the right way to do it in a way that the body doesn't just simply adapt in a homeostatic mechanism for.
Dr. Scott Watier: [00:18:21] And if you're listening, you're like, well, I started fasting, I lost twelve pounds or, you know, someone's done our challenge. They lost we had one person who's eighteen pounds in ten days when we did the ten day challenges. Right. And they're like, wait a minute. Well, isn't adaptive thermogenesis or part of this whole problem, like isn't rapid weight loss potentially lead to that? And yes, it can. But when you add in the balancing of the hunger hormones, the decrease in the insulin resistance, which is your body's inability to process to get you into fat burning mode, to process the food and the fuel that you're bringing in. So interspersing those periods of food, feast versus famine or food. You know, versus fasting, however you want to look at it, you're going to get the best of both worlds, you're going to be able to stoke the fire short term and then avoid the pitfalls of the old model. Right, that we really talk a lot about. And we juxtapose how we used to live until how we live now and how a lot of our you guys listening live because you're adapting that fasting lifestyle. So I just love the fact that it's it started from a place of, oh, let's make sure that there's not something here that could be, you know, slowing the metabolism. And that's why I like the fact that this looked at thirty eight different studies, you know, different there was a whole wide breadth of randomized versus non randomized versus observational studies, et cetera. So not all the best cream of the crop stuff, but the fact that we can look at it and say, OK, for the for the common person who's looking to lose weight and never put it back on, here are the few things that we can do.
Dr. Scott Watier: [00:19:57] You can put in fasting, using fasting windows from 18 all the way up to seventy two hours. Typically you're going to range in that 18 to 30 to thirty six hour mark. Throwing in a longer fast every now and then is good to keep, to keep mixing it up and to push your boundaries and to learn how to interpret hunger cues and build healthy relationship with food. But again, we always talk about beginning with the end in mind, which is making sure that we get the result. And for the first time ever in my life of dealing with being the heavy guy over 20 years was I finally got to keep it off and kind of give like the proverbial middle finger to to the to the failures of the past and say, you know what? No, I've got it. I figured it out. But it's always going to take that repetition. And one of the fears, like you had mentioned, is, OK, am I going to crack my going to crash my metabolism or is this going to you know, is this going to become a problem long term? And the reality is, no, as long as you keep varying as you add in, the exercise and consistency is the key. Long term, if you adapt this as a lifestyle, you're only going to see the rewards and the benefits.
Tommy Welling: [00:21:09] Yeah. And you know something you said a minute ago about the interspersing the periods of time that you're that you're in that caloric deficit versus the times that you're not. That was one of those things where being very much in the black and white perfectionist mentality, I had done low and slow for a long, long time. And it was it was one of those things where it was hard for me to understand why that would be beneficial. It was I'm not sure why. I just kind of had a mental block towards it. But but physiologically speaking, it it makes sense because then we are we are kind of undoing what what the body's trying to adapt to. So, you know, kind of reversing the effects of that, that homeostasis where the body gets comfortable and figures out how to adapt to what you're doing. So putting in those those times where you're through in a longer, fast this week, OK, well, maybe it's time to go a few days or maybe a week or so where where you're not pushing you're pushing the gas so hard and OK. Now this week's just kind of a maintenance week. And then I'm going to jump back into a more more of a fat loss mode the following week after that. And it makes sense. And it's a way to to stay out of that kind of homeostasis.
Dr. Scott Watier: [00:22:21] So if we had to distill this down, I'm going to put you on the spot here, Tommy, and have you on the plane, as we like to say, lady, four episodes into this fascinating four life podcast journey. Shout out to you guys, the listeners to we just it's thank you for the five star reviews. Those are our favorite kinds. This lifestyle may not be for everyone. Our message may not be forever. And the good news is, is that the people that we have reached, it's now hundreds of thousands of you guys, which is just incredible to think when we started this. Tommy, we like to give you something to go do, right? Yeah. So some of these are more conversational. Some are more anecdotal. Sometimes you get a little nerdy, but we always like to walk away with something that is actionable that you can go try you can give us feedback on and you can put into your day to day life. So if we had to land the plane with one action step, what do you got?
Tommy Welling: [00:23:14] Well, I you know, we've said that the interval thirty six hours several times throughout this. So I'm going to encourage everyone that a thirty six hour fast is something that most of your or most of my friends and family have not done a thirty six hour fast. So if you're if I get that going OK, well I haven't done that before. How do I do that. The easiest way to do it is going to be to have breakfast tomorrow and dinner the following day after that. That's probably the easiest way to do a thirty six hour fast because you don't have to go a full day without eating anything. It's just just an easy way to kind of get into it and feel the benefits of it and and then just kind of expand your boundaries from there.
Dr. Scott Watier: [00:24:01] Yeah, and that's going to be a direct way, contrary to the the the the title of the summary that I read, which was, you know, does weight loss result in is it true that weight loss can result in a slow metabolism? Right. You're going to get that thirty six hour boost. Right. So you're going to get that a direct way to actually go in boost your metabolism is doing that. Thirty six hour fast. So if you're listening to this some some sometime on Tuesday, which is the day the episodes typically drop, then you will want to eat breakfast if you catch it early enough on Tuesday. Right. And then eat dinner on Wednesday. Or if you're listening to this later in the day on Tuesday, then you can simply just eat breakfast on Wednesday. And then wait to have dinner that following Thursday, and you will have accomplished a new way or a new tool in your fasting tool belt, if you've never done that exact fasting window before, why not give it a shot? There's a lot of cool physiological things that take place. And I just want to mention the new resource, Tommy, that we have on the website as well.
Dr. Scott Watier: [00:25:06] So if you're new to fasting, you might be like 36 hours you. I'm not ready for that. Let me get it. So go ahead and go to the fasting for life dotcom. You can download the Fast Start guide. We have a new resources page that has the Fast Start guide, as well as the new free resource, which is the insulin assessment and the insulin, we think. And a lot of cool feedback on the insulin assessment. And we're just going to continue to build this stuff out based on the common roadblocks or feedback that we get. So go check those out, go to the website. If you're more of a beginner, download both honestly, because they're both really awesome in our opinion. But we might be biased. So download the Fast Start guide for to get a perspective on how to increase your fasting window and put one meal a day fasting injured and a life for you. Long term listeners are more experienced pastors. Drop that thirty six hour fast into your week and then go ahead and download the insulin assessment as well. Any final thoughts today, Tumi, as we wrap up?
Tommy Welling: [00:26:07] Yeah, and then Posture Review and post your questions. Tell us how it's going and and ask questions. Submit submit questions for our next Q&A that we'll be doing as well.
Dr. Scott Watier: [00:26:17] So thank you, guys. Yeah. Yeah, we yeah. We love info and fasting for life dotcom info at fasting for life dotcom shoot as a message shoot. It's a question and we aggregate them and then we do a periodic question and answer podcast episode. So as always, Tom, thank you for your conversation. Thank you for your insights. And we will talk soon. Thank you. Bye.
Tommy Welling: [00:26:42] So you've heard today's episode and you may be wondering where do I start? Head on over to the Fasting for Life Dotcom and sign up for our newsletter where you'll receive fasting tips and strategies to maximize results and fit fasting into your day to day life.
Dr. Scott Watier: [00:26:56] Why are you there? Download your free Fast Start guide to get started today. Don't forget to subscribe on iTunes, Spotify or wherever you get your podcasts. Make sure to leave us a five star review and we'll be back next week with another episode of Fasting for Life.
The Fast Start Guide takes the guesswork out of using intermittent fasting. Your guide will be immediately delivered to your inbox, giving you the confidence to get started now!