Torwen:
Hello and welcome back to the Ideal Nutrition podcast. My name is Torwen. I’m here with my co-host, Aidan. Today, we’re going to give you an insight into six things we’ve changed our minds on. Aidan, would you like to start?
Aidan:
Sure. I’m excited for this. We haven’t spoken about this off air. So, I don’t know what you’ve changed your mind on. I don’t know if you checked the outline, but I put mine in there. I’m going to start with the first one: metabolic adaptation versus metabolic damage. I changed my mind on this quite some time ago.
For my format, I’m going to start with why I thought what I used to think. Then I’ll explain why I changed my mind. So, previously, there was a concept called metabolic damage. I still think a lot of people believe this concept as well. It is the idea that if you spend many years dieting, your metabolism could be permanently suppressed. It could also happen if you did a very aggressive diet. Your metabolism could be almost permanently suppressed, even many years later.
I’ve spoken about this a bit on the podcast. One of the reasons I believed this was the Biggest Loser study. Six years after the show, their BMR was about 500 calories lower than you would have otherwise expected. To be fair, it was not quite extreme in their case. Their basal metabolic rate was still quite high, at over 2000 calories. Their total daily energy expenditure was still well over 3000. But I would always look at that through the lens of empathy.
And I would think, hang on. Having a BMR be 500 calories low is like perpetually dieting at a 500-calorie deficit. It is like doing that just to maintain your weight. That was one of the biggest pieces of evidence I went with. The second piece of evidence was working with people. There were a lot of people reporting quite low calorie intakes. Their body was also not responding how I would have expected.
So, what made me change my mind? The first thing was seeing all of the other research. As each study came out, I also looked at studies that were already available. The picture was painted in a way where we had one study showing one thing. Then every other study was showing something different. Basically, all the other research shows that the body cares far more about what we have done recently. It cares more about that than what we did many years ago.
Metabolic adaptation goes in both directions. If we end up in a calorie surplus, our metabolic rate increases a little bit. Metabolic adaptation goes in that direction. If somebody hypothetically lost heaps of weight, then regained weight over time, it should adapt in the other direction. It is also a relatively short-lived thing. If somebody is at maintenance calories for about four weeks, it is usually back to normal. That is apart from extreme circumstances.
You can then go back to the experiences of working with clients. The thing that changed my perspective on that is this. To this day, we still do not have cases with people being on quite low calories, with all food provided, not losing weight. We see it heaps in the real world. But we also have all this data on underreporting existing, showing how prevalent it is. And we do not have anything showing this in controlled environments. That moved me towards metabolic adaptation going in both directions.
Torwen:
Love that insight. I think there are a few things that might pop up as we go along today. Two of them are probably more research and looking at more research. Also, working with clients in a space can definitely change your opinion on certain things. So, my first one is GLP-1 medications. I used to be pretty cautious of GLP-1 medications. That was especially true when they first became a thing while I was still at uni.
Everyone was talking about this magical Ozempic that would help with weight loss. And that was before I did more of my own research. It was also before I worked with clients who take GLP-1 medications. I still think there is nuance around when these medications should be prescribed. But I generally think I have come around a corner. And I can see how incredibly effective they can be for appetite regulation.
They can also help with blood sugar control and weight management. That is particularly for those who have struggled with long-term lifestyle approaches alone. And, in research, they consistently support 15 to 20% extra weight loss on top of placebo. That is clearly extremely significant. While I still believe they are not a replacement for a healthy lifestyle, I do think differently now. When combined with proper nutrition advice and exercise, they can be a powerful addition for some people.
Aidan:
I had a similar learning during university. Obviously, this was quite a few years ago. I graduated 10 years ago. So, we are talking about a bit under 15 years ago. I remember sitting in the lecture, and they brought up bariatric surgery. At that time in my life, I expected them to talk about it negatively. I thought they would say we should just focus on nutrition and exercise. They talked about it through a neutral lens instead.
They spoke about how we could help somebody who had undergone bariatric surgery. And I was very surprised by that. Then, when I went into practice, I worked with people who had undergone bariatric surgery. It suddenly became a real interest area of mine. There are many reasons why that is the case. I now view GLP-1s as a scaled-back version of that. They have less downside and less permanency as well.
Torwen:
Interesting.
Aidan:
Yeah. The next one is total protein needs for optimising muscle growth. I have shifted my mind on this. I will say I have changed my mind a little bit in terms of my public message. But behind the scenes, I will use the phrase shifted my mind a little bit. I will explain why I believed what I believed. Then I will explain why things changed. The range I used to typically recommend was 1.6 to 2.2 grams per kilogram of body weight per day. There were two major reviews from very smart people that made me believe that. One was a narrative review from Brad Schoenfeld and Alan Aragon.
They were talking about how much protein the body can absorb in a single sitting. And they made an argument for total protein needs being more important. But they also argued that this still mattered. They went through basically all the research. They concluded that muscle growth seems to be maximised around 1.6 grams per kilogram for basically everyone. Then they put a confidence interval above that at the 2.2 range. This was to cover outliers, because we know outlier ranges will exist.
That was around 2016 or 2017. Then, in 2018, there was a study looking at protein supplementation. And it was a meta-analysis. It did the same kind of review. And it came to the conclusion that muscle growth was maximised at 1.62 grams per kilogram. It also had the same kind of confidence interval at 2.2.
I thought, hang on, these two major reviews have come to the exact same finding. That is what I am going to go with. A lot of people in the evidence-based community were also doing the same. I do not like to think I am smarter than other people in that space. There were people much smarter than me also saying this number. But there were a few reasons that had me questioning it still.
Reason number one, bodybuilders have always gone higher than that. If you look anecdotally, there is observational research looking at bodybuilders. It shows almost everyone is doing 3.0-plus grams per kilogram. I still would not just go based on that. There is the potential that they are doing that despite the research. And it might not actually be helping. Maybe it was maximised around two grams per kilogram. But they are just having more, and that is fine.
Reason number two is possibly the bigger one. Every time I opened a study comparing 3.0 grams per kilogram versus 1.6, 3.0 would always outperform. The 1.6 target is where muscle growth is theoretically maximised for most people. But I would open the study and guess which one led to more muscle growth. I would always be right that the higher one led to more muscle growth. I was like, how is this true? So, I had those things in the back of my mind. When working with people, I would always still go on the higher side of things.
The thing that changed my mind was an article by Stronger By Science. I realised while prepping this that I am going to credit the same people twice. That is not a great look, but it is what it is. The article basically explained why it is time to move beyond the 1.6 to 2.2 grams per kilogram range. It made a really compelling argument for why that range should be revisited. One of the things they did was chart out the research.
It was Morton et al. I have not put it in the show notes for this, but it is the 2018 review. They showed on the chart that even in that study, going higher than 1.6 led to more muscle growth. I thought, well, that is pretty cut and dry. It is very simple. They also showed more recent research since then that supported that. They made the point that there is not much research that goes much beyond that. But what is pretty clear is that there are diminishing returns. And going above this range is probably leading to slightly more muscle growth. But it also cuts into your opportunity to get other nutrient-rich foods.
So, where I stand now is this. If somebody’s sole goal in life is to maximise muscle growth, going well above that range probably makes sense. I am fully supportive of that. But there is a cost to doing so in other areas. If somebody wants to build heaps of muscle, and do 95% of what they can do, I have simplified it. I now say two grams per kilogram of body weight is probably a good target for somebody in that position.
Torwen:
Yeah, I think that makes a lot of sense. I think adding some context for our listeners helps here. Obviously, Aidan works a lot with very active people who lift a lot of weights. They may have a lot more muscle mass and a higher calorie expenditure. So, they can eat a lot more food. If they are still meeting their other nutritional requirements, going a little higher than 1.6 makes sense. That makes sense if there is space to do so.
Aidan:
That is definitely the case with bodybuilders as well. You look at some of the calories they get up to. There is space, and there is room for this. If they were not doing this, they would need to have quite high carbs. They likely are doing that anyway. Or they would need to increase their fat higher. After a certain point, that probably does not make sense either.
Torwen:
Now, Aidan does not know what my next one is. But it ties in quite perfectly. It is protein absorption in a single meal and where we should set that target. For a while, it was widely spread that you cannot absorb more than 30 grams of protein in one sitting. The rest was supposedly just wasted. That is something I do not think I ever believed. But again, if you do not have the knowledge, it makes sense. When I was in high school, I wanted to build muscle. I was like, yeah, 30 grams of protein sounds perfect. Now I view it a little differently.
The truth is that, of course, you absorb more than 30 grams. There is not really a doubt about that. Calories and amino acids do not just completely disappear. Your protein is broken down. It enters your bloodstream regardless of how much you eat. It is going to be there. The 30-gram idea comes from research on muscle protein synthesis. It relates to how much can be used to stimulate muscle growth.
Some studies still support that muscle protein synthesis peaks around 20 to 40 grams of protein in a meal. And that is how much will stimulate muscle building. But it is not how much is absorbed. So, there are definitely some flaws in the interpretation. Absorption does not mean everything is used for muscles. Amino acids from protein are also used for energy, repair, enzymes, hormone production, and other metabolic needs.
The second thing is that whole meals can also change the response. Having carbs and fats slows digestion. This can potentially extend the time that amino acids are available in the blood. So, higher protein meals could still be beneficial. And like Aidan has been chatting about, total intake matters so much more. Long-term research supports that total daily protein intake is more important for muscle gain. It matters more than capping meals at 30 grams.
If you are looking at a bigger athlete, capping meals at 30 grams might not work. They might not reach that total intake across the day. So, I would say still aiming for 1.6 to 2.2 makes sense. Distributing that over the day at around 0.4 to 0.55 grams per kilogram of body weight also helps.
Aidan:
Yeah, that latter point was the one that always got me. I remember seeing some content in the rugby league world. I will not name them. But they were saying that 30 grams is the limit. I get that 30 grams is simpler than adjusting based on body weight. But I really hope they are not saying this to their front row. I really hope that is not what they said. You have found a way to make them worse at their sport if that is the case.
Torwen:
Even if we do some maths, let us say you have a 90-kilogram athlete. That is probably on the lower end for a rugby player. If we go with two grams, that is roughly 180 grams of protein. If you are only having three or four meals with 30 grams of protein, it will not quite cut it. It is not going to cut it.
Aidan:
Yeah. Absolutely. The next one I changed my mind on is PCOS and basal metabolic rate. I was uncertain about this one and would sit on both sides of the fence. Now I firmly have a position on this. There are many reasons why losing weight with PCOS can be harder. Starting with what made me think what I thought. Very early in my career, probably in my first year as a dietitian, I knew PCOS came with challenges. But I was not an expert on PCOS at that time.
Fun fact, or little flex, at one stage if you Googled PCOS nutrition, a blog post by me came up. That was quite a few years after this. I spent some time learning. But in my first year, I did not really know that much about it. I was watching a TED Talk about nutrition and PCOS. They talked about a study that found a lower basal metabolic rate in people with PCOS. It was somewhere between 17 and 40% lower. It also scaled based on insulin resistance.
The people who were the most insulin-resistant had the lowest BMR. The people who were less insulin resistant had slightly higher BMRs. It was almost building a case that we just need to address insulin resistance. Then it would solve that and make weight loss easier.
That was interesting. I had questions about it in my mind for quite a few years. The first question was that we do not see that in any other area. We do not see that in diabetes. You do not just solve insulin resistance and people drop weight. Metformin is a great example of this. When people go on metformin for 12 weeks, you might see one or two kilos of weight loss. That is as an average. But it is not like addressing insulin resistance leads to large weight loss.
If you wanted to debate metformin usage, pick other medications that address insulin resistance. We do not really suggest that addressing insulin resistance leads to significant weight loss over time. So why would PCOS be different? I came across another person in the nutrition space who made an argument about why PCOS is different. They talked about intrinsic insulin resistance versus extrinsic insulin resistance. I will not go too deep into that. But that was one of the first things I questioned.
The second thing that put me on the fence was looking at research myself. At that time, I found four studies that looked at BMR. Three showed that people with PCOS had similar BMRs to those without PCOS. That was assuming all other variables were equal. Then one found a big difference. When working with people, I came across a lot of people where we had this conversation. We talked about weight loss being more difficult with PCOS.
I would talk about this as a potential factor. But I did not really know where I stood. Even so, it does not really change what we do. We still need to find where the sweet spot is to create a calorie deficit. So, it is information. But it could just be a challenge that we choose to overcome if relevant.
The thing that changed my mind was, unfortunately, also Stronger By Science. I promise I read way more content than this. It is shocking that I have done two in one. Stronger By Science did this article breaking down the concept. It showed that basically it is not different. An odd thing about this one is that they found something like 19 studies. Plenty of research had come out since I first looked. But of the four I found, there were probably another four out there at the time.
I missed a bunch as well. They basically found that of around 19 studies, one found this reduction. About 18 did not find a reduction. Then, in this massive article, they went much deeper. Without directly accusing this lab, they showed that this lab had dodgy readings. That was with their resting metabolic rate testing equipment. They were getting readings that just did not make sense. Some people had metabolic rates measured at around 500.
Others were above 3000. You do not really see either of those. Who has a resting metabolic rate of 500? If you ignored that study, you would assume PCOS and BMR are normal on average. We have done content on this. There are many other reasons why weight loss can be harder with PCOS. It is just that basal metabolic rate is normal in that case.
Torwen:
That is some awesome insight for people listening. Whatever we do with clients, we still try to find where that active deficit is for them. My last one is around intermittent fasting and not eating first thing in the morning. I used to be quite anti-intermittent fasting, full stop. Now I see it with a bit more nuance. In the past, if a client came to me and was not eating breakfast, I would always recommend adding it in.
I still stand by the fact that breakfast is such a useful meal. It supports good nutrition generally. It is often a meal where we can get in a decent amount of protein. We can also get whole grains and fibre. It supports appetite regulation later in the day as well.
I now see more nuance around different preferences and eating patterns. People have different eating patterns that work for them. If there are no issues around bingeing or overeating later in the day, I am more okay with it. That includes people who prefer intermittent fasting.
It also includes people who just prefer starting eating later in the day. Especially if weight loss is the goal, it can be linked to a lower calorie intake. That is when it is done correctly. As long as overall general nutrition is adequate, I am happy to support that.
Aidan:
Yeah, absolutely. A curious one I have is some gut-health-related stuff. If somebody was not having breakfast, some forms of fibre might be less likely to be had. That includes certain whole grains and things like that. You might also run the risk of needing a lot of fibre close together. That is if you are trying to get to a good fibre target.
But as a general thing, I do not think that is too big of an issue. The other one I have is if meal frequency gets too low, nutrient absorption can be an issue. We have not spoken about it in this podcast. But in the last podcast, we spoke about iron and calcium. We also spoke about a few other things. If somebody took it to an extreme and did one meal a day, that will most likely have issues. But from an overall health perspective, intermittent fasting in general is clearly fine.
Torwen:
Yeah. As long as we can make sure that you get the nutrition you need across the day. Again, there are instances where I will still advise against it. I might say, hey, for you, I do not think it is worth doing. If you are an athlete and need to refuel after a session, there is no reason to wait for hours. But if it is your personal preference, I am more open to telling you how we can do that safely.
Aidan:
Absolutely. Well, cool. We will wrap up here. Hopefully you found that interesting. I do not know if people listen at home and think, I cannot believe you changed your mind on that. You should have known that from the start. But everyone changes their mind on stuff. So, it is what it is. We will wrap up there. If you have not already, please leave a rating and review. We would massively appreciate it.