**EP336: Time-Restricted Eating & Lipoprotein A**
**Dr. Auric Bishop:** Welcome, my name's Dr. Auric Bishop. I'm a cardiologist, an author, and a keynote speaker. I'm the CEO of the Healthy Heart Network. I'm all about trying to help people live as well as possible for as long as possible. Heart disease is huge in Australia. Every 20 minutes, someone suffers a heart attack. Most of these could probably have been avoided if only we knew what to do. This podcast is all about helping you understand blood pressure, weight, cholesterol, for better health. If you enjoy this podcast, I would be honored for a five-star review. You can share it with your family and friends. It may well save someone you love.
Hi, welcome to my podcast and videocastation. My name is Dr. Warwick Bishop, and I really do appreciate you tuning in. Today, I'd like to talk about two different things: time-restricted eating and lipoprotein little a.
One of the things that has become more and more prominent in recent times has been fasting. As part of that fasting, people talk about skipping days or the five-two diet, which means you'd eat pretty normally on five days out of a seven-day week. For two of those days, you would have a significant calorie restriction. A fellow called Dr. Moseley made that particular diet quite popular. Since then, we've seen a discussion, particularly in social media and, to a degree, in scientific circles, around time-restricted eating.
The 16:8 arrangement, where people might eat within an 8-hour window and have 16 hours of fasting, has been advocated for its benefits, such as improved insulin resistance and weight loss. Let's put the eating to one side and think about other things that we might do to maintain our health. Often, we'll look at fasting for weight loss. A good number of my patients will explore it in that regard.
The other thing that we can do for weight loss is exercise. Exercise obviously has different components to how it can be delivered. One of the most significant ways that we hear talked about is high-intensity interval training, or HIIT training. This is really a variant on going pretty well full tilt for a short period of time, having a break, and repeating that several times. This can be done once or twice a week. The idea is that you're really pushing the way your muscles, in particular, are able to extract oxygen from the blood. This gets measured through what we call VO2 max, which is an indication of your fitness.
What I'd like to share with you today is a study called the PLOS ONE study. Feel free to go and look it up if you're curious. This study looked at the question: does time-restricted eating help with weight loss and other cardiovascular parameters? Does high-intensity interval training help with different cardiovascular parameters, including weight loss? The last question asked is, by combining time-restricted eating and high-intensity interval training, do we get even more bang for our buck?
The researchers of this particular study pulled together about 60 individuals to put through a study protocol. Approximately 20 went through the time-restricted eating group, just over 20 went through the high-intensity interval training group, and about 20 went through both time-restricted eating and interval training. Each of those cohorts lost a couple of people. So, respectively, it was 23 enrolled, 27 enrolled, and 24 enrolled. Then, respectively, from time-restricted eating, three lost weight; from high-intensity interval training, three lost weight; and from the combination of high-intensity interval training and time-restricted eating, four lost weight. This probably tells us that that slight increase in demand of well-restricted eating and discipline in terms of exercise took its toll.
After this randomization, these 20-odd individuals in each of those subgroups were tracked for 12 weeks. The cohort was predominantly women, all with BMIs over 30. This was a group of ladies who were carrying excess weight, making it an ideal cohort to ask the question: what can we do to help? The intervention lasted for 12 weeks. At the end of that time, there was a collection of data, including blood tests, weight, and body composition.
Interestingly, all three diets appeared to lead to weight loss. The combination of the two diets resulted in the most weight loss. BMI, similarly, was most significantly reduced through the combination of high-intensity interval training and time-restricted eating. When they looked at waist circumference, which is a very important indicator of potential metabolic issues and therefore cardiovascular risk, each of these interventions—time-restricted eating alone, high-intensity interval training, and the combination—lowered waist circumference. However, time-restricted eating was the least effective, high-intensity interval training was the next most effective, and the combination was the most effective.
Interestingly, when they looked at fat-free mass, it appeared that the high-intensity interval training and the combined high-intensity interval training and time-restricted eating group were the ones that showed an increase in fat-free mass. The time-restricted eating group alone showed a reduction in fat-free mass. What does that mean? It means that by not exercising, as your body loses weight, it loses both fat and muscle.
A really important component of this body composition evaluation is that the incorporation of high-intensity interval training ensured that not only was muscle mass maintained, but it was improved. This is very important if we're looking to reduce weight over a period of time, but also looking to reduce frailty down the line.
When it came to dietary intake, quite interestingly, right across all the groups, people ate less. That was particularly the case in the time-restricted eating group, but interestingly, the high-intensity interval training groups also ate fewer calories, which is a little bit counterintuitive and not exactly what we'd think if we reflect on our own habits, as we often feel hungrier after exercise. Nonetheless, this is what they observed.
In terms of glucose levels and insulin resistance, there were no surprises. By fasting, we improve insulin sensitivity. By exercise, we improve insulin sensitivity. As you might expect, the combination of the two performed better than either alone.
When it came to LDL cholesterol, the so-called bad cholesterol, the combination of time-restricted eating and high-intensity interval training actually resulted in nearly a 40% reduction of LDL cholesterol, which is about the same as a low-to-intermediate-intensity statin. Now, this is really valuable information and incredibly important for us to bring to that conversation of patient care in situations where individuals are very keen to do the very best they can to manage their cardiovascular risks through intervention alone.
Blood pressure, as you might guess, improved as weight came down and insulin resistance improved. Both systolic and diastolic pressures improved. So, what does this tell us? Probably what we might have guessed intuitively from what we've seen, but this is a scientific representation. This is the first time that I'm aware of a paper like this being done, certainly confirming that time-restricted eating is beneficial in terms of weight loss and cardiovascular risk, but it doesn't really maintain muscle mass as weight loss occurs.
High-intensity interval training and high-intensity interval training in combination with time-restricted eating have all those same cardiovascular benefits at a slightly higher level. As you might expect, there is an additive role. Most importantly, high-intensity interval training maintains and improves fat-free mass, meaning that people retain muscle. That's super important as we age.
I hope I've given you something important and valuable to consider in your own habits and practices. I have to share with you that my own habit is time-restricted eating. I tend to eat probably in a 6:18 or 8:16 habit, meaning I eat in an 8 or a 6-hour window most days. Why do I do that? Well, I've found that it's helpful for my arthritis. I get a bit of arthritis in my thumbs. If I digress from that particular habit, I find the arthritis in my thumbs flares up.
There was one other thing I wanted to share today, and that was about lipoprotein little a. I had a patient the other day with an elevated lipoprotein little a. No question, it was above the 80th percentile. We know that lipoprotein little a is associated with increased risk of cardiovascular disease, cerebrovascular disease, and increases the risk of aortic stenosis. This patient was in their 60s, but let's say for argument's sake they were in the range of 60 to 70. So, old enough as a female for that lipoprotein little a to have had an effect.
This patient presented with a raised lipoprotein little a level and a zero coronary calcium score and wanted to know why they didn't have a problem. The reason for mentioning that is to highlight that what we see is only a fraction of what we understand. LP little a is broadly associated with increased risk but appears causative in specific individuals. For this woman, it was simply an association, and to be honest, we can't be sure if the structure—the molecular structure, the series of amino acids—that could be involved with her lipoprotein little a specifically for her could alter charges on it, alter particle function such that it was less likely to deposit.
It might be that this particular patient had such low other cardiovascular risks that lipoprotein little a never really came into play. The take-home message from that is that it's useful to check those cardiovascular risks. For this particular patient, I probably wouldn't have even bothered checking the LP little a if I'd known she had a zero coronary calcium score as a starting point. I think going to that final common denominator is a very valuable starting point for evaluating risk, so we can get that separation between association and what's actually going on.
Well, time-restricted eating, high-intensity interval training, the combination of both, lipoprotein little a, and the role I still believe of imaging to guide our understanding before further testing—I'll leave all that with you. It's been a delight to share. I hope you've got something really positive from this. If you do enjoy these podcasts, please share them. I would be really grateful for you to do that and leave a positive review. I'd like that too.
Till next time, I wish you the very best. Please live as well as possible for as long as possible. Take care and bye for now.
**Dr. Auric Bishop:** Hi. Ever wondered what your risk of heart attack is? You should. It's the single biggest killer in the Western world. We're talking one death less than every 30 minutes in Australia, one death less than every 60 seconds in the United States, and 9 million deaths globally per annum. Well, how do you check your risk? You can go to www.virtualheartcheck.com.au. You'll find out about your risk and what can be done beyond that to be even more precise.
