Jim Hill:

Welcome to Weight Loss And, where we delve into the world of weight loss. I'm Jim Hill.

Holly Wyatt:

And I'm Holly Wyatt. We're both dedicated to helping you lose weight, keep it off, and live your best life while you're doing it.

Jim Hill:

Indeed, we now realize successful weight loss combines the science and art of medicine, knowing what to do and why you will do it.

Holly Wyatt:

Yes, the “And” allows us to talk about all the other stuff that makes your journey so much bigger, better, and exciting.

Jim Hill:

Ready for the “And” factor?

Holly Wyatt:

Let's dive in.

Jim Hill:

Here we go. Holly, today we've got something pretty big to talk about. For years, people have asked us, is intermittent fasting actually better than just cutting calories? Well, we finally have a long-term clinical trial that begins to answer that question.

Holly Wyatt:

You're right, Jim. And I am so excited for this episode. This is one of the most anticipated studies. We've been waiting for this study to come out. And this study isn't short-term. This is a year-long study where we talk about the difference between, if you can do, we're going to talk about a certain kind of intermittent fasting and then traditional caloric restriction. Which is better? And a long-term randomized control trial. That's what we love. So I'm really excited about what we're going to talk about.

Jim Hill:

We're honored to have the lead author of the study with us today, someone that you and I know very well, Dr. Vicky Catenacci. Vicky's a nationally recognized expert in obesity treatment and nutrition science. She's a physician and clinical researcher at the University of Colorado Anschutz Medical Campus, where she focuses on innovative strategies for sustainable weight loss. Vicky's part of the NORC there, and we talk about NORCs, Nutrition Obesity Research Centers, all the time. We like to have people from NORCs on the show. And you and I were fortunate enough to get to work with Vicky for several years, and we've done studies together, and we've watched her really emerge as one of the real superstars in this area.

Jim Hill:

Vicky's led numerous clinical trials on lifestyle intervention. Her work continues to shape how we understand and treat obesity in the real world. Vicky, welcome to Weight Loss And.

Victoria Catenacci:

Thank you so much. It's so great to be here with you guys.

Holly Wyatt:

Before we even get into the details, this study is about something called 4:3 intermittent fasting, or I'm interested to see how you say it, Vicky, but 4:3 intermittent fasting. What is that, first off?

Victoria Catenacci:

Yeah, so that's a great question, Holly, because I think there's so much confusion, about intermittent fasting and there's so many different paradigms. And even other physicians are confused about this. Patients are confused about this. And so I think it's really important to kind of understand what we're talking about here. There's a number of intermittent energy restriction paradigms. There's time-restricted eating, which I kind of view as a separate category. That's where you limit your eating window every single day, typically to an eating window of less than 8 to 10 hours a day. But again, that's a strategy where you have to focus on that and do that every single day. This paradigm is different. It's more about sort of what I think of a true intermittent fasting, which is picking several days a week to significantly restrict your energy intake and then eating normally on the other days of the week. And so there's a number of flavors of intermittent fasting, including the 5:2 paradigm, where you fast two non-consecutive days a week, 4:3, which is the paradigm we studied, where you fast three non-consecutive days a week. And there's also a paradigm called alternate day fasting, where you just, it's exactly what it sounds like, you fast every other day. There have been studies of zero calorie fasts, where you eat nothing for those fast days. Those have kind of petered out because it seems like that's just too difficult for most people. And so most of these intermittent fasting paradigms involve a modified fast on the fast day, but with a pretty significant energy restriction, so greater than 75%. So that operationalizes in our study to around 500 to 600 calories for women and about 600 to 700 for men on those fast days.

Jim Hill:

So why did you choose the 4:3, Vicky? And what do you tell people? What are the instructions you give to people?

Victoria Catenacci:

Yeah. So that's a really good question why we chose 4:3. There were a couple reasons. So our pilot study was actually zero calorie alternate day fasting. And people did that for eight weeks. And that was very difficult, but it produced pretty significant weight loss. But it just wasn't really sustainable. The feedback we got was that it was just too hard to really do those zero calorie fasts. So we looked more towards a modified fasting paradigm. And really, the choice of 4:3, it's interesting, was driven by the study design in some sense, because we wanted a daily caloric restriction group. We wanted these groups to be matched for the targeted weekly energy deficit. And I think that's a really important feature of our study and an important feature to evaluate when you are kind of reviewing these trials and trying to make sense of them. So we wanted to match the targeted energy deficit, but we didn't want that targeted energy deficit to be too low or too high. We wanted it to be kind of reasonable for a daily caloric restriction diet, but also kind of fair to the daily caloric restriction. So we were looking for something that would produce a weekly target deficit of around 30%. And so 5:2 was too little. The alternative day fasting was too much. And so 4:3 sort of seemed to be that intermediate choice.

Jim Hill:

So if I were going to come in and be on the 4:3, what would you tell me to do?

Victoria Catenacci:

Yeah, so what we did in our study was we actually ramped people up. So we didn't have them start with three fast days a week. So we wanted to give them a little kind of a little taste of it. And we wanted to be able to provide them some behavioral support. So we had them do one fast day for the first week, then two for the second week, then three for the third. In our study, we actually measured resting energy expenditure, and we were able to give everyone an individualized fast day goal so that we were perfectly matching our DCR, daily calorie restriction group. But practically speaking, that didn't really matter. The fast day calorie goals were all pretty similar, again, in that 500-ish range for women and 600 for men. So that's probably what I would suggest. We learned a lot from our participants in terms of how they sort of what seemed to work best. So when people tried to just eat little bits throughout the day, anecdotally, it felt like that was really hard. They never felt full. And then they were always having to kind of track and add up.

And oftentimes they went over their goal. So we ended up encouraging people to eat their fast day calories in a single meal. So you would really actually be able to feel hungry, feel full after that meal. Most people prefer to do that at dinner so that they would, you know, fast during the day, make sure they were staying well hydrated. They could have non-caloric beverages like black coffee or flavored waters. And then they could kind to have a normal meal with their family. And then we had a very strong behavioral support curriculum and encouraged healthy eating and portion control on the non-fast days, but they did not have to count calories and they didn't have to consciously restrict on those non-fast days.

Holly Wyatt:

So basically three days of 500 calories, and then the other four days, they kind of could do what they wanted, although there was probably a little bit of behavioral support in those days.

Victoria Catenacci:

Yes. So not feast days. I think sometimes in these sort of true intermittent day on, day off paradigms that I call the Fed Days Feast Days. And I think you can do a lot of damage.

Holly Wyatt:

Yeah. No, no, no feast days. I don't like that either.

Jim Hill:

Wait, before we get to the results, I want Vicky to talk about this is a long term study.

Jim Hill:

Why are these studies so rare and so difficult to do from a researcher point of view?

Victoria Catenacci:

Because they're just really hard. I think it's, you know, the recruitment is hard. I think recruitment for behavioral weight loss trials is now a little bit harder with the new highly effective anti-obesity medications. And that was sort of coming on during the tail end of the trial. Cohort three, our middle cohort, was at week 14 in March of 2020. So we went from a study where we were delivering everything in person to overnight having to shift the entire intervention to Zoom.

Jim Hill:

Wow.

Victoria Catenacci:

In the middle of cohort three, we were doing non-contact pickups of monitors and drive-bys. We got shut down for about two months. Luckily, it was between our outcome measures. And then we were lucky in that I framed our research reactivation as a treatment study, treatment for obesity. And so we were able to be in the first group, like the group A studies that were able to get reactivated very quickly. But that was a huge challenge. And then kind of finishing out the study through cohort four was totally Zoom. Cohort five, we were able to get back in person. But keeping people in the study is hard. And just the running the study is hard. We also did double-label water to get objective energy intake and expenditure, which we can talk about more. And that was just hard.

Holly Wyatt:

Yeah. What the listeners maybe don't realize is when did you start this study? What was the year?

Victoria Catenacci:

2018

Holly Wyatt:

2018. And here we are in 2025 and the results are coming out. That's how long it takes.

Victoria Catenacci:

Take it back even before that of when did I first submit this grant, Holly. I remember sitting with you and being like I don't know the day it was going in you're like "I don't like your entry I think maybe you should switch them out." And I'm like, "Oh, Holly, you're killing me." And yeah, I mean, of course, you're always right. So, we make those changes in the grant. But yeah, I think that's really important to understand about research is that there's so much thought and planning that goes into it and securing the funding because no company is going to pay for this. No drug company is going to pay for this. So it's all NIH funding, which is just so important in the current environment to sort of recognize where this science comes from. I think we were a little bit delayed because we had such significant building access restrictions that we couldn't get our staff in the building to do data entry and data verification. We were just using all of our staff building access to actually run the study. So then we were so behind on data entry. It took us a while to get caught up. And just then the publication process was almost a full year of back and forth.

Jim Hill:

But it's so important to do these longer term studies. But I think our listeners get a sense of why there are so few of them, because it's so difficult to do it.

Jim Hill:

So you've spent five, six, seven years to get to this point. But these studies that follow people out for a long time are so essential to really understanding what happens.

Victoria Catenacci:

Yeah, I think they are. The short-term studies just really don't give you the full picture. I thinkHolly learned that with the CARB study, the short term results. What people can do for 12 weeks is very different than what they can do for a year. And I would love studies that were more like three to five years, because that's what's really important in weight.

Jim Hill:

That's the next 20 years of your life, doing a five-year study, Vicky.

Holly Wyatt:

All right.

Jim Hill:

All right. Let's talk results, Holly.

Holly Wyatt:

Yes. So this was a randomized controlled study. So you had regular people restricting calories kind of the regular way every single day. And you got to compare it to this. And what did you find? That's what our listeners, which was better? They want to know, I'm sure.

Victoria Catenacci:

Yeah. So we actually, it was really funny. I'm almost embarrassed to say this. So, you know, we like to have fun in our lab. When we were sharing the results with the rest of the team, Danielle and I did a gender reveal. So we did a results reveal and we had those like, you know, those.

Holly Wyatt:

Yeah, that shoot up colors or whatever.

Victoria Catenacci:

Shoot up the colors.

Holly Wyatt:

Yeah.

Victoria Catenacci:

We did a whole gender reveal with the results. We did one color for IMF and the other color for DCR. And we did it out on a big lawn outside the wellness center. So the exciting thing was that 4:3 IMF was statistically significantly better than DCR. And the difference was modest. And I think that's really important to understand. Like, I don't feel like this is a strategy that's going to work for everyone. I think it's an additional evidence-based alternative. So DCR lost...

Holly Wyatt:

What's DCR? I don't know if we...

Victoria Catenacci:

Daily calorie restriction. Sorry, I've spent 10 years.

Holly Wyatt:

Daily calorie restriction. Okay.

Victoria Catenacci:

Yes. And the goal was 34% every day. So that's even a little more aggressive than, you know, than we usually target. And they had 34 group-based behavioral support sessions and access to a fitness center. And at one year, they lost 5% of their body weight. And in 4:3 IMF, they lost 7.6% of their body weight. And that was in all participants. And actually the results were interesting. So we were about 70 people Right around like 75% women, which is, you know, to even get 25% men in a weight loss study is pretty good. But when we looked at women only, there was actually an even greater difference. So women in 4:3 IMF lost 7.4% of their body weight and women in DCR lost 4.2%. So it's interesting because usually men do better in everything at weight loss, but it seemed like this strategy seemed to be particularly helpful for women and produce a greater differential in weight loss.

Jim Hill:

So both groups lost weight. It's that the 4:3 group did a little bit better, lost a little bit more weight over this period of time.

Victoria Catenacci:

Yes. And keep in mind, you know, and I know that those weight loss results are relatively modest, but we also had, you know, cohort three, like, hit with the shutdown right at month, you know, month three, and then cohort four was really, you know, still in the midst of COVID and lots of stress and doing everything by Zoom. So I think when we looked at the data, those two cohorts removed, the results looked a little bit better, but obviously we have to...

Holly Wyatt:

Vicky, stop underselling this. This was a great study. These are great results. You kept these people in the study, the fact that they... I mean, this was a huge study.

Jim Hill:

This is an amazing study. You look at the study, everything was done the right way in this study. So it's an answer that we can be pretty comfortable represents reality.

Victoria Catenacci:

Yes, thank you, Jim. I appreciate that.

Holly Wyatt:

See we have so many questions. This is what Jim and I do. We go like boom boom boom.

Jim Hill:

I got a bunch of questions so hurry up and ask yours so I could ask mine.

Holly Wyatt:

All right. Geez. So body composition One thing I think about when you kind of restrict calories and you're not fasting, you have 500 calories so it's not complete fasting, but you know one day or three days a week you're only having 500 calories. Does that do anything in terms of, I guess, metabolism? That's one question. But the second question is, do you lose more muscle mass because of that or were they the same?

Victoria Catenacci:

Yeah, they were really the same. The percentage of fat mass loss versus lean mass loss was the same in the two groups. And they tracked the same as weight loss. So nothing really magical. At least, again, we weren't powered for those outcomes, but nothing magically different in terms of what we saw in terms of lean mass loss and fat mass.

Holly Wyatt:

Or not worse, because I might think it could be worse.

Victoria Catenacci:

Not worse. No.

Holly Wyatt:

Not worse. Yeah. All right, Jim. Go ahead.

Jim Hill:

Thank you, Holly. Vicky, what about adherence? Did you find that one group was more adherent than the other group?

Victoria Catenacci:

Yeah. So the first interesting thing was retention.

Jim Hill:

Ah.

Victoria Catenacci:

We found that. So overall, we had about 75% of participants stayed in the study, but we had about 30% drop from the DCR group and only 19% dropped from the IMF group. So we had more people stay in the study in the IMF group. And that was all, you know, all that was accounted for in the modeling analysis thatPAN, our statistician, did. Dietary adherence. So this is, I think, a unique strength of this study in that we had a very objective measure of energy intake. So many studies rely on self-reported energy intake, which we know, you know, everyone's bad at self-report. Physicians, RDs, normal weight people, people that struggle with their weight, no one is really good at reporting what they eat. And so knowing that and knowing that we would really, at the end of the day, want to know what was driving differences between the groups. We used double labeled water to measure energy expenditure at several time points throughout the study. And then we were able to adjust that based on the change in body energy stores from the DEXA scan, fat mass, and lean mass, and get an accurate idea of how many calories people were eating over the intervention. And so we found that at one year that the 4:3 IMF group was restricting their calories by about a little over 10% from baseline. And the DCR group, and this is over the whole year, it kind of averages, it's like an A1C in that it averages the calorie intake over the entire duration of the study. In the daily caloric restriction group, they restricted by about 5%. So we're both way below the weekly targets, which we kind of know about how difficult it is to stick to diets. But the adherence to the diet, at least as measured by the overall percent calorie restriction, was better in the 4:3 IMF group.

Jim Hill:

This is important because most studies ask people what they eat. And we know that that's a little bit like throwing darts. And it's not that people cheat. It's hard to know that. The method she used, so you've got three variables. You've got change in body composition, energy expenditure, and intake. If you measure two of those accurately, which she did, you can estimate the other one very accurately. So this is like head and shoulders above what's usually done, which is just using self-reports of intake.

Holly Wyatt:

And I love it because it fits with what we said. There wasn't magic here. It was about restricting calories. The group that was restricting the most calories lost the most weight, you know, versus what we hear out there. Oh, it doesn't matter. You know, calories don't matter. They're, you know, blah, blah, blah. No. When you use this technique that really gets at what are they eating, it fell right in line with it is about energy restriction for weight loss. And the more you restrict, the more weight loss you get. So I think you proved that, Vicky. That's something.

Victoria Catenacci:

Yeah, we were really excited about those results too.

Holly Wyatt:

But why behaviorally maybe? So you know that they restricted more calories, but why do you think the 4:3 group did better, was able to restrict more calories maybe?

Victoria Catenacci:

Yeah. So I have several ideas on that because I think about this study a lot.

Victoria Catenacci:

So my first thought is that I think it's so much easier to do something more restrictive a few days a week than it is to restrict modestly every day. I think it's really, really hard to do something every day. You're always feeling restricted. You're always thinking about food. You're going to bed hungry. You're waking up hungry. I think that's really hard for people. And so in some ways, for some people, not for everyone, it may be easier to significantly restrict a few days of the week and then not have to worry about it the other days. I think counting calories, meal planning, you know, tracking, all of those things that are involved in daily calorie restriction take a lot of executive function. They take a lot of planning ahead. It's a big cognitive load. So doing those things every day, it's really hard to adhere to over time. Another thing is that you don't get any do-overs in daily calorie restriction, right? You have a bad day. You can't go back in time and fix things. I mean, I guess you could restrict more the next day, but then that makes it even harder. So with IMF, the nice thing is you have the opportunity to have a bad day and give yourself some grace and self-compassion and say, "Okay, I tried a bad thing today. It didn't work. I'm going to try again tomorrow." And you can still get to your calorie goal over the course of the week with a little bit more self-compassion and forgiveness there.

Holly Wyatt:

And also maybe kind of match your schedule. So I know I have a birthday party on Friday. I'm not going to make that one of my 500 calorie days. I can see that being helpful.

Jim Hill:

Well, Vicky, I think you definitively, with this study, legitimize this form of calorie restriction as a reasonable thing to do. And again, so many things out there, we just have no doubt on. Does that work? Does it not work? What you've shown, this is a legitimate way to lose weight and restrict calories. Now, what I'm really interested in, my guess is there are going to be some people that really do very well with the 4:3 and others, it's just not their bag. And as we more and more recognize, not everybody does well with the same strategies.

Jim Hill:

What can you learn in the future about that?

Victoria Catenacci:

Yeah, that's a great question. And so we, in kind of anticipating that question, because that's what I love to do, when we designed this study, we tried to incorporate as many of the ADOPT measures. So this is the NIH working group that kind of set up this framework of, you know, these are the things that really should be done in all weight loss studies to help us understand that exact question. What are the individual specific factors that predict response? Because ideally, you're absolutely right. You want to be able to match the diet to the person. So we have collected, I think Danielle calculated out like 91% of the biologic, behavioral, psychosocial, and environmental variables that were recommended by this ADOPT working group for weight loss studies. And so we have all that data now to sort of explore.

Jim Hill:

You can predict, maybe.

Victoria Catenacci:

We're hoping. We've got a few kind of interesting analyses. One is looking at intervention preference. So some simple things like what did people prefer at baseline and whether they, if they got randomized to their preference group, did that improve outcomes or not? We have census track data on built environment. We have tons of eating behavior questionnaires, both at baseline and throughout the study. So really trying to understand if there are things that can predict response. But my sense is I'm not convinced we're going to find anything earth shattering. And so I think it's really trial and error. I think people can give it a try and see if it seems to resonate with them. And if it does then stick with it.

Jim Hill:

I agree with that. I think when you want to do dietary changes like that, it's okay to try out some things. Back with the low-carb diets, when we started doing low-carb diets, people thought it was snake oil, it was crazy. And we learned that as a short-term tool, they're fine. Now, long-term, people have difficulty adhering to them, but we need to give people different options, I think, which is not a one-size-fits-all.

Victoria Catenacci:

I totally agree. That's what the hope is with this study, that it gives people another tool, you know, in the toolbox.

Jim Hill:

Yes.

Holly Wyatt:

So I know Jim is going to want to talk about physical activity because it's coming, Vicky, so get ready. But before we get to physical activity, I just want to make sure, because you're an MD, were there any safety concerns? Binge eating, did it bring out eating disorders? Because I hear that a lot. Well, if I start restricting that severely, that may bring out an eating disorder, for instance.

Victoria Catenacci:

So a couple of things about safety is that, you know, there were definitely groups of people we did not include in the study. And you know that I'm very conservative. And so we did not include people with diabetes. We did not include older adults. We didn't include children. We didn't include pregnant women. We didn't include people with heart disease or significant kidney disease. And we didn't include people with eating disorders. That being said, there were really no safety issues. I think we had four diet-related adverse events, all in the IMF group, but all mild. Things like, you know, weakness, jitteriness. No one had to drop from the study due to a diet-related adverse event. And we had nothing that was beyond mild. So I think that was really reassuring. Interestingly, we looked at binge eating behaviors with the tool called the binge eating scale. Again, it's self-report. We didn't observe these people, but at least based on what they reported, what was super interesting is that binge eating behaviors actually got better in 4:3 IMF and they got worse in VCR. And that is in our manuscript. And we've got data from the three-factor eating questionnaire that showed a similar trend with uncontrolled eating. And so, I mean, I don't want to make too much of that, but it really just reassured me that at least in people without a history of eating disorders at baseline, that it definitely didn't worsen that binge eating.

Holly Wyatt:

You weren't creating them. It does not appear to. So that is something good.

Victoria Catenacci:

Yeah. And I think that's really important because I think that's a big concern I hear about these more restrictive paradigms. But I think people found that they didn't have to eat just because it was mealtime. And that sort of translated a little bit to their non-fast days.

Jim Hill:

Yeah. So Holly's put me on the spot with physical activity. So I'll go ahead and ask. I assume both groups were given the same recommendations for physical activity. What were they and what interesting things, if any, came out around physical activity?

Victoria Catenacci:

Yeah. So because I trained with you, Jim, I know the importance of physical activity. And so we gave them all a prescription to increase moderate intensity aerobic activity to target of 300 minutes a week over the first six months. They got kind of a gradual ramp up. They got support for that during the group-based behavioral support. And they also got access to the fitness center for a year because we felt like we really wanted to make sure that there wasn't any inequity in terms of everyone having a safe, place to exercise than everyone having access to a fitness center. And I think it's a really important question because we know how important physical activity is, maybe not as much for short-term weight loss, but for long-term maintenance. We wanted to make sure that intermittent fasting didn't adversely impact people's ability to increase their physical activity. And there was really no signal that that was an issue. Both groups increased their physical activity as measured by inclinometer, accelerometer device. So it was another objective measure, not self-report, you know, by roughly an hour a week with no significant difference between groups.

Holly Wyatt:

I think that's important because a lot of times people feel like, all right, I get this question. If I don't eat food, if I cut my calories, you know, significantly to 500 calories, I'm not going to have energy to exercise that day. I shouldn't exercise if I'm going to be eating that low of a calorie level. But that didn't seem to be true in this study, correct?

Victoria Catenacci:

It didn't seem to be. And I think the flexibility of the 4:3 allowed people to switch up their fasting days with their exercise. Again, I think if you're training for a marathon, if you're training for triathlon, yes, this is probably going to affect your performance. But for 45 to 60 minutes of walking a day, which is kind of what we were recommending, I don't, you know, I think it's not as much of an impact.

Jim Hill:

So Vicky, I'm looking at your paper right now and your changes in body weight. And it's very interesting because in the constant calorie group, it looks like they maximized their weight loss at about three months, stabilized for a while, and then they're gaining back a little bit. The 4:3 group actually continued to lose a little longer to six months, and it looks like they're maintaining their weight loss much better.

Jim Hill:

So the question is, is this a long-term strategy for maintenance for these folks? Do you think they're interested in doing that? would they continue to use such a strategy?

Victoria Catenacci:

Yeah, I think that's a great question. We have six-month data that we're working on, so we'll have another time point in sort of a more real world setting where they didn't have access to the fitness center, where they didn't have all that behavioral support. And then we've actually submitted a grant to look at to see if we can bring them back at like a five to seven year follow-up and see how they're doing, along with getting some other measures, including measures of biomarkers of aging to see if maybe those were impacted as well. But I mean, I think, again, anecdotally, the things that we hear from participants are that they've tried other things, that they've never been able to stick to something and that this is something that they feel that they may be able to continue with. Now, that's not everyone. I've had people tell me this is drip. And for some people, it's really hard and they really didn't like it. And it's probably not the right diet for them.

Holly Wyatt:

This is interesting. So you said it was around 7% in that group, right?

Victoria Catenacci:

A little over 7%.

Holly Wyatt:

A little over 7%. Did people feel like that was enough weight loss? Are they still wanting to lose more? With the new GLP-1s, the big difference is they produce a lot more weight loss. And that's gotten people to a level where they're like, yeah, this is the amount of weight loss I wanted. 7% is kind of sometimes not quite enough for people.

Victoria Catenacci:

Yeah. And I think that the waterfall plots and the variability are just like we see with any other study. We have people in both groups gaining weight. And then we have people with bariatric surgery levels of weight loss, you know, 20 to 30% in both groups. And so there's such individual variability. And I think there's such individual variability in what people's weight loss goals are. For some people, they're happy if they can just stop their gain and improve their health a little bit. For other people, they want to fit in their high school prom dress. And so I think it's a hard question to answer. I think probably most people were, I would say, somewhat satisfied, but I think most people always want to lose more. And now that we have these medications, I remember, Jim, you telling me, oh, in the early 2000s, like, if we can find a medicine that produces 15% weight loss, that's just going to be, that's just going to change everything. And I think you were absolutely right, as always, that, you know, that with highly effective anti-obesity medicines that can produce those levels of weight loss, I think the expectation is a little bit different. Unfortunately, those medications aren't accessible to everyone due to cost, side effects, insurance coverage.

Jim Hill:

Yeah.

Holly Wyatt:

But Vicky, maybe this is what you do to maintain. This may be a tool to maintain or something like that. So putting all the tools together.

Victoria Catenacci:

And Holly, you've always been so forward thinking in that aspect of like, maybe of really, I mean, both of you thinking of weight loss and weight loss maintenance as really separate phases and what you have to do in weight loss to create a deficit versus what you have to do in weight loss maintenance to stay in energy balance at that new reduced body weight.

Jim Hill:

I think this can be a tool for weight loss maintenance. Vicky, I think this is an amazing study. And I know you had a whole team of people that contributed, but this is the kind of research that really does help us move forward.

Jim Hill:

So my question for you is what's next for you? Where do you go from here? What's the next wonderful study that you're going to do?

Victoria Catenacci:

Yeah. So carrying this forward, we actually just piloted this intervention in a small group of breast cancer survivors. So that is a population for whom weight management is so important in terms of reducing risk for recurrence. Reducing risk, reducing all-cause mortality, but for whom there are so many challenges with weight loss because of both the weight-promoting effects of chemotherapy, and in particular, the anti-endocrine therapies. So we sort of modified this intervention and kind of tailored it with cancer-specific nutrition and exercise information and piloted it over three months in a group of 15 breast cancer survivors, stage one to three disease who had completed their primary treatment. And we actually just submitted a bunch of abstracts for that for the obesity society meeting. So stay tuned for those results. But in brief, you know, the intervention was, it was really more of a feasibility and acceptability pilot study because with a small study, it's hard to draw meaningful conclusions about clinical outcomes. But the ratings we got on something called the net promoter scale, which is, you know, we ask people like, how likely are you to recommend this to your friends and family? And how did you like this intervention? And it goes from minus 100 to 100. And our ratings were like positive 50 to 60, which is just really kind of reassuring that people really like this intervention.

Victoria Catenacci:

And the feedback we got was really positive. So, we're excited about those results. And I'm looking at submitting an R01 for a larger efficacy trial compared to DCR in that population.

Jim Hill:

Fantastic. Well done. Holly, do we have time for some listener questions?

Holly Wyatt:

I think so. I have one right here that I think will be good. So this comes from a listener. Do you have to do the fasting part forever to keep the weight off or can you phase it out?

Victoria Catenacci:

Yeah. I mean, I think that goes back to what we were talking about with the weight loss phase, where you really need that energy deficit and the weight maintenance, where you need to still probably reduce from what you were eating before, but not as much as you had to for weight loss. And so I would kind of think of maybe transitioning to one or two fast days a week and seeing if you can maintain and kind of titrating up or down, depending on how your weight was doing with that.

Jim Hill:

All right. Here's one. Vicky, is it okay to exercise on a fasting day or should you do your exercise on the days you're not fasting?

Victoria Catenacci:

Yeah, I think that's kind of an individual preference. Again, if you're, and it depends on the type of exercise you're doing. If you're walking your dog for 45 minutes, that's probably okay to do on a fasting day, as long as you're making sure that you stay hydrated. If you are doing vigorous cardio, that may be a little bit more difficult and you might want to kind of focus those sessions on your non-fasting days.

Holly Wyatt:

Yeah, or I always say, use your 500 calories around that session. If you need, some people like to eat before, some people eat after, but kind of target them to that session. I have one more that I think would be good. Does intermittent fasting mess with your metabolism? We've told people for a long time, when you fast, or you eat too few calories, it could have an effect on your metabolism. Any results on that?

Victoria Catenacci:

Yes. So that's a really interesting question. And we have some data, but not the right, not the perfect data to answer that question. So what I can say is that we measured resting energy expenditure throughout the study. And we've actually published this data. We found that neither group, that the fasting intervention didn't have any kind of negative impact on resting energy expenditure. And there was actually a trend for REE to decrease less in the 4:3 IMF group. But the problem is, is the way we did all of our measures. So the REE was done, we didn't want it after a fast day. So we did it after a fed day in the 4:3 IMF. And in DCR, it was done after they were restricting every day. So it wasn't really an apples to oranges comparison. So we're being a little bit careful with that data and making sure that we don't overstate the implications. Ideally, we would have had a post if I could have gone back and done it again. And actually, I wanted to do this and somebody could talk me out of it. But a post-fed and a post-fast are more on an average.

Jim Hill:

That would have been great.

Victoria Catenacci:

Way to answer that question.

Jim Hill:

All right, Holly, you know what it's time for now?

Holly Wyatt:

The favorite questions, Vicky. I don't know if you know what these are. You know what's coming?

Victoria Catenacci:

No, I don't know what's coming.

Holly Wyatt:

The vulnerability questions where we ask you something personal, something vulnerable.

Victoria Catenacci:

Okay. I'm good at that. I'm open to share it.

Holly Wyatt:

Okay. Start it off, Jim.

Jim Hill:

All right, Vicky, you did a study on 4:3 intermittent fasting. Did you try it yourself? And if so, how did you handle it?

Victoria Catenacci:

Yeah. So I had everyone on my team try it because I felt like if we were going to be telling our participants to do it, that all of our staff needed to kind of experience it. And so everyone tried it and everyone had kind of different responses. Some people loved it. And in fact, a couple of them like are continuing to do it. Some people hated it. for me, I like it. I definitely incorporate it into kind of, you know, I'll kind of have some fast days during the week. And then on the weekends, I definitely have my fed days. And I wouldn't say I'm as structured as like a 4:3, but I've definitely incorporated the philosophy into how I approach eating.

Jim Hill:

Cool.

Holly Wyatt:

Yeah. So I want to try it this way. I can't wait to try it. So I've got one more for you in vulnerability. If you could erase one myth about intermittent fasting, what would it be?

Victoria Catenacci:

I think it's the binge eating myth. And I actually, even in just doing some of the media interviews for this and seeing some of the articles that they've come out, there've been some commentaries that people have written about yes but we don't recommend this because it can worsen binge eating. And I feel like anytime you say something without evidence, that's dangerous. And I think we've shown evidence that at least in people without eating disorders, it doesn't worsen binge eating. And so I think that's a myth that I would like to try to erase.

Jim Hill:

Okay. Very cool. All right. Let's get to some takeaways. Vicky, what's one thing you would like our listeners to take away from this study?

Victoria Catenacci:

I would say that this is an evidence-based strategy that can be considered within the range of dietary paradigms for weight loss. And that weight loss is not a one-size-fits-all approach. And the best approach for any given person is the one that you can adhere to over time. So, as you said, Jim, sometimes weight loss is trial and error. Smoking cessation, people typically have to try seven times before they figure it out. And so, you know, maybe be open and be vulnerable and try something new and see how it feels.

Holly Wyatt:

Love it. That's great.

Jim Hill:

All right. Vicky, thank you for joining us for this.

Victoria Catenacci:

Thank you so much for having me. It's been so nice to see you and reconnect.

Jim Hill:

Well, this is such an amazing study and you have emerged as really one of the stars in this field. And I can't wait to see all the other wonderful research that you're going to do. So it's been fabulous having you on. Congratulations on this study. It's impactful. It's very meaningful for our listeners. It's very well done. So thank you.

Victoria Catenacci:

Thank you. And coming from you, Jim, that really means a lot. I appreciate that.

Holly Wyatt:

All right. And for our listeners, we would love to hear your experience with fasting, with doing this and also any other topics you want to hear about. So let us know, send us your questions, and we'll keep doing this.

Jim Hill:

See you next time on Weight Loss And.

Holly Wyatt:

Bye, everybody.

Jim Hill:

And that's a wrap for today's episode of Weight Loss And. We hope you enjoy diving into the world of weight loss with us.

Holly Wyatt:

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Jim Hill:

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Holly Wyatt:

And remember, the journey doesn't end here. Keep applying the knowledge and strategies you've learned and embrace the power of the “And” in your own weight loss journey.