Intermittent fasting may benefit in metabolic syndrome
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Patients with metabolic syndrome who limited their eating to a 10-hour window in addition to statin and antihypertensive medications had reductions in weight, BP, HbA1c and atherogenic lipids, according to a study published in Cell Metabolism.
As the concept of time-restricted eating, also known as intermittent fasting, grows in popularity, more research must be conducted to learn more about its benefits, particularly regarding CV health. This research conducted by Pam R. Taub, MD, FACC, director of the Step Family Cardiac Wellness and Rehabilitation Center and associate professor of medicine at University California, San Diego, and colleagues serves as a jumping point.
Healio spoke with Taub about what was learned through the study, how patients and cardiologists should approach time-restricted eating and the potential mechanisms behind the approach.
Question: What are some of the major takeaways from this study?
Answer: One of the big issues with this concept of intermittent fasting is there is a lot of uncertainty about what is the right approach. There are some people that want to do a week of fasting or 2 days of fasting. There are a lot of crazy regimens out there.
What we wanted to do is in a very scientific way study a regimen that we thought was very practical and could be implemented long term by patients. We studied a type of intermittent fasting called time-restricted eating, and that involves fasting for 14 hours with an eating window of 10 hours. We studied that in patients who have metabolic syndrome or prediabetes. We found that this was a window that resulted in benefits in terms of lowering of the LDL cholesterol, decrease in weight, decrease in BP and it was also a safe regimen. That’s one thing we always need to keep in mind is the safety of this regimen because some of the longer fasting regimens are not safe for patients that are on medications such as antihypertensive medications.
Q: What is the potential mechanism behind these improvements seen in patients with metabolic syndrome?
A: The mechanism still needs to be investigated. We have an NIH-funded study to look at the mechanisms further. The hypothesis is that when you go into a state of fasting, especially over 10 hours, you deplete the body of its glucose reservoir. After the glucose is depleted, your body starts mobilizing energy from fat leading to lipolysis. That is probably one of the ways that you are reducing weight by utilizing the fat storage.
The other mechanism that I think is at play is ketosis. More than 10 hours of fasting results in a low-grade state of ketosis, and ketosis results in lipolysis (break down of fat into free fatty acids which can function as a high energy fuel for cells). We believe this mobilization of fat stores may be responsible for the weight loss and other metabolic benefits we saw in our study.
My personal hypothesis is that this state of fasting also makes the mitochondria more metabolically efficient. We’re testing this in our current study that’s NIH funded by taking patients, again, with metabolic syndrome and having them fast for 10 hours. We’re also doing skeletal muscle biopsy, analyzing the mitochondria and looking at if the mitochondria become more efficient in terms of adenosine triphosphate production and other parameters.
One of the reasons that I hypothesized about the improvement in mitochondrial efficiency is because patients were telling me that they felt that their energy levels and their endurance improved. That’s another reason why I wanted to investigate it in a more scientific way is because of this self-reporting patients had about energy levels.
There are a couple different mechanisms at play, but the overarching theme is an increase in metabolic efficiency in the body because one of the things that we’re seeing is the benefits that we see go way beyond just reducing calories. For instance, when you lose 3% of body weight, other studies have found that your LDL cholesterol decreased 3% to 5%. In our study, there was a 3% reduction in weight, and that resulted in an 11% reduction in LDL. There are effects that go way beyond what you would expect from a small reduction in calories that occurs. In our study, there was about an 8.6% reduction in caloric intake. It was not something that we told the patients to do. We didn’t give any instructions about reducing their calories. It was an inadvertent thing that happened because their eating window was restricted and they ended up consuming fewer calories.
Q: Is time-restricted eating meant to be a short-term or a long-term approach?
A: This is meant to be a long-term, lifelong measure because it is something that is doable. Patients that have CV risk, it’s meant to be a lifelong measure. There is a lot of flexibility with it. For instance, in our animal study, we found that if the animals could adhere to time-restricted eating for 5 out of 7 days, they had benefits. What I tell my patients is if you can do this 6 out of 7 days or even 5 out of 7 days a week, you’re going to get some benefit. Ideally we’d like them to do it as many days as possible.
The other thing about time-restricted eating is that there is some flexibility. You don’t have a rigid window that you can only eat from 8 a.m. to 6 p.m. You can adjust the window based on your schedule. If you have an appointment or a dinner meeting that’s a little bit later, you can do that, but just start your breakfast a little later on. There’s a little bit of flexibility that’s built into time-restricted eating.
What most people will find is once they start this regimen, they feel better. In our study, we report an improvement in sleep quality. That is self-sustaining. When a lifestyle intervention leads to improvements, people tend to adhere to it. People often feel they have more energy, they feel more well rested when they do this type of regimen. That does lead to long-term adherence.
What we’re really doing is going back to the way humans were meant to consume calories, which is over a smaller period of time than what we are doing in current societies. It also goes back to the circadian rhythm. Aligning our eating patterns with circadian biology is thought to be one of the reasons time-restricted eating is so beneficial.
Q: Do you think there’s a patient population where this approach may not work or may be frowned upon because it may be causing more harm than benefit?
A: The population that is most likely to benefit from time-restricted eating are people that are overweight, they have elevated BP, they’re trying to lose weight, they have CV risk factors. That’s the population that we studied.
In terms of a very healthy person where all of their parameters are completely normal, they’re not going to get as much benefit. I still think there is a benefit in restricting caloric intake to 10 hours. They will still get improvement in sleep and in energy levels.
The patient population that needs to be very careful with this type of regimen and hasn’t been studied is insulin-dependent diabetics. By that, I mean patients who are very brittle diabetics. We need to do more research into that population to see what the best strategy for them is.
Q: Are there any harms in going to extremes with time-restricted eating with longer fasting periods?
A: When people do things in extreme ways, there are sometimes adverse sequalae. One of my patients was on a diuretic, was trying to lose weight, read a story online about fasting for 48 hours and how it resets everything. She did it, but ended up passing out because she was dehydrated and hit her head. She syncopized because of doing a regimen that wasn’t really validated and tested and without consulting her physician.
No matter what the regimen is, no matter how benign it seems, a physician does need to be involved. For our patients with metabolic syndrome, one of the things that happened at the end of the study was when parameters got better, I lowered medication. If they stayed on higher levels of their antihypertensives, they may have gotten hypotensive. All of these regimens, even though they seem like a simple lifestyle regimen, you still need to get your physician involved. If there are medications that patients are on, there needs to be attention to adjusting them based on some of the improvements that patients get with this type of regimen. – by Darlene Dobkowski
For more information:
Pam R. Taub, MD, FACC, can be reached at University of California, San Diego, Division of Cardiovascular Diseases, Department of Medicine, 9434 Medical Center Drive, La Jolla, CA
92037; email: ptaub@ucsd.edu.
Disclosure: Taub reports she consults for Amarin, Amgen, Boehringer Ingelheim, Janssen, Novo Nordisk, Pfizer and Sanofi/Regeneron and is a stockholder of Cardero Therapeutics.
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