In this interview, News-Medical speaks to Dr. Satchin Panda about his latest research into time-restricted eating and how it can be used to manage metabolic diseases.
What provoked your latest research into time-restricted eating?
My lab started the concept of time-restricted eating or what is now popularly called intermittent fasting. My lab studies circadian rhythm, which is the internal timetable for our body to carry out different tasks at a pre-determined time of the 24 hour day.
We found that when animals and humans eat is the most powerful way to sustain a healthy circadian rhythm. When we have a robust circadian rhythm, our body can be at optimum metabolism, physiology, and brain function. Hence, we started exploring how limiting the time of eating without any change in nutrition quality or quantity can maintain optimum health and prevent diseases.
I must emphasize that TRE does not depend on reducing calorie intake, while the term “fasting” typically means reducing calories for at least one or few days in a week. Hence, we coined the term TRF or TRE. Besides, most people with obesity or metabolic conditions, who would benefit from this approach are repelled by the word “fasting”. So, the term TRE is more acceptable.
Can you describe what intermittent fasting is and what it involves?
The term “Intermittent fasting” broadly refers to any dietary approach that involves fasting or reducing calories for one or more days in a week or month. It typically refers to alternate day fasting, 5:2 diet, periodic fasting, and so on. The scientific basis for each of these approaches overlap but are not identical. Many forms of intermittent fasting are also not recommended for people with type 1 and type 2 diabetes.
Time-restricted eating refers to a dietary practice in which people consume all of their daily calories within a consistent window of 8-10 hours every day. Unlike “intermittent fasting” (as defined in scientific papers), it does not require counting and reducing calories any day. Although there are several popular approaches to it, we have found in our research that an 8-10 hour window is acceptable to most people, and they can keep up the habit for years. The 8-10 hour window also does not trigger any adverse effects such as nausea, lightheadedness, excessive hunger, or feeling of hypoglycemia as is found in many studies where people followed a 4 or 6-hour eating window.
Although there is some suggestion that the TRE window starting early in the morning is better than that starts around noon, there is no definitive study that has compared these practices and found any significant advantage of one over the other.
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Can you describe how you carried out your latest research into time-restricted eating and metabolic disease?
The article is a review of the literature including some in our lab. We do Time-restricted feeding/eating research in both laboratory animals (TRF) and human clinical studies (TRE). In the laboratory, we subject mice to eat within 8-10 hours during their wakeful hours. These mice, even when given unhealthy food, remain healthy, can perform better in exercise tasks, and in some cases live longer.
In human clinical trials, we ask our participants to self-select an 8-10 hour window that works best with their lifestyle and try to eat within this window for at least 12 weeks. We measure their health through vitals and blood work before and after the intervention. (In both animal and human studies we also have control cohorts who are allowed to eat whenever they want.)
In some of our human studies, we have recruited patients with metabolic syndrome who are on medication to control their blood sugar, blood pressure, or cholesterol. Even these patients who are taking medication to manage their metabolic diseases can adopt 10-hour TRE and see further improvement in their blood pressure, blood sugar, and cholesterol. They also feel more energetic and report restful sleep. Even if they can follow TRE for 5-6 days a week, they seem to reap many health benefits.
We have developed and deployed an academic research app “myCircadianClock” that is used in all of our clinical studies to track when people eat and through the app we also offer educational materials and guidance for people to adhere to TRE. User engagement through the app is a powerful approach to guide and monitor how people eat before the intervention and how they adopt TRE.
What did you discover?
Please see above. We also find that many (not all) individuals following TRE also inadvertently improve their nutrition quality. They tend to eat bigger breakfast (or first meal), reduce snacking, and reduce alcohol intake. This unintentional improvement in nutrition quality may further help them in reaping better health outcomes.
We have also made the “myCircadianClock” app available for anyone to download and share their habitual eating habit. From these “baseline” data we find only 10% of adults eat consistently within a window of 12 hours or less. That means almost 90% of people have the potential to adopt TRE in their lifestyle.
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What other benefits does time-restricted eating have?
In both animal and human TRF/TRE studies, we also find improvement in gut health, brain health, and immune function. Many individuals with acid reflux report better gut health and reducing in the frequency of acid reflux. People sleep better; some sleep slightly longer and some get uninterrupted deep sleep. The sleep improvement may explain why some animals that are predisposed to neurodegenerative diseases also stay healthier on TRF.
Surprisingly, we find animals undergoing TRF improve their immune system so that when they are challenged with infectious agents, they mount a balanced immune response and do not die from the infection. These “other benefits” open the door for future studies to test if TRF/TRE can be a lifestyle habit to manage diseases of the gut, dementia, and infectious or autoimmune diseases.
Are there any concerns someone should take into account before starting time-restricted eating?
As I mentioned earlier, 90% of people eat for >12 hours. So, eating within a 12-hour window is somewhat safe and is a good first step for most people to practice every day. Those who have an underlying medical condition that makes it essential that they eat for more than 12 hours, should consult their doctors.
People with type 1 diabetes or those with type 2 diabetes with insulin therapy or on certain medication must consult their doctors before adopting a 10 or 8-hour TRE protocol. They may require close monitoring, medication adjustment and some may not find it easy to adopt an 8-hour TRE.
People taking any medication for other chronic conditions (blood pressure, cholesterol, inflammation, an autoimmune condition, heart condition, weight loss medications, etc) should also consult their doctors as TRE may lead to medication adjustments (typically lowering the dose or changing the meds).
Some people who are already eating healthy, in moderate quantity, and have normal healthy weight may be eager to adopt 6 or 8-hour TRE. They should watch their diet as some may inadvertently reduce total calories to a dangerously low level. Particularly for women, such low-calorie intake combined with prolonged fasting may have an adverse effect on reproductive health.
Do you believe that if more people suffering from chronic diseases such as diabetes and heart disease started time-restricted eating, they would be able to better manage their symptoms?
Yes, they are most likely to benefit from 10 hours TRE. But they should consult their doctors.
What are the next steps for your research?
We will continue our laboratory work to understand the genes, molecules, and cells that are affected by TRF in different organs and brain regions. This fundamental research will offer new clues to the disease conditions that can be better prevented or managed by TRF/TRE.
In humans, we will continue our collaborative clinical research on the impact of TRE on managing metabolic syndrome, and type 2 diabetes.
We also hope more and more people with diverse backgrounds and of all ages would use our free research app – myCircadianClock – to share their daily habits and health status data. These data will help understand the barriers to TRE, who are more likely to adopt TRE, and what types of benefits they experience. These data are valuable for guiding basic and clinical studies for improving the health and performance of everyone irrespective of age, gender, work schedule, health, and socioeconomic status.
Where can readers find more information?
myCircadianClock.org.
This website offers many educational materials in the form of blogs and links to videos.
Anyone can also give informed consent and download the app to start self-monitoring their daily habits and adopt a TRE lifestyle.
About Dr. Satchin Panda
Dr. Satchin Panda is a professor at The Salk Institute, California, where his lab works on the basic and translational research on Circadian rhythms. His research in four major areas are relevant to healthy aging.
1. His discovery of a blue light sensor in the retina has led to human-centric lighting in built environment to optimize sleep, mood, and brain function.
2. He discovered that eating within a consistent 8-12 hours, called Time-restricted eating or intermittent fasting, can prevent or reverse chronic diseases and increase healthy lifespan.
3. Circadian genomics studies in primates have identified the dosing of the majority of FDA-approved drugs can be optimized to the right time of the day to reduce adverse effects and improve efficacy.
4. Finally, his lab, along with others, has demonstrated drugs targeting circadian clock components are a multi-solving approach to treat chronic diseases, including liver disease, cancer, and Alzheimer’s disease.
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