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Satchin Panda, Ph.D. (@SatchinPanda) is a professor and the director of the Regulatory Biology Laboratories at the Salk Institute for Biological Studies. His research explores the genes, molecules, and cells that keep the whole body on the same circadian clock.
Andrew Huberman and Satchin Panda discuss his lab’s discovery that “time-restricted eating” (TRE) aka intermittent fasting, benefits metabolic health and longevity. They dive into the tenants of TRE, what constitutes fasting and breaking fast, improvements to mood and cognitive performance, the timing of light exposure for circadian regulation, levers to pull for physical and mental health, and so much more.
Host: Andrew Huberman (@hubermanlab)
Books: The Circadian Diabetes Code and The Circadian Code by Dr. Satchin Panda
The foundation of fasting is really restricting calories and playing with feeding times to optimize health
Fasting 2 days on, eating 5 days has been shown to improve weight maintenance and signs of aging in healthy humans and pre-diabetes
Intermittent fasting: umbrella term for intensely reducing calories 1-2 days per week or a few days throughout the month
Time-restricted eating (TRE): confining energy intake (liquid and food) within a consistent feeding window of 8-12 hours
Feeding versus eating: breaking a fast is consuming something that triggers a rise in blood glucose – it’s hard to provide a hard and fast rule since metabolism and activity levels vary
As an aside, it’s ingrained in us to eat and socialize in the evening – this goes back to our caveman days when we learned to control fire and gathered around and continued throughout history
As long as TRE is not less than 12 hours, it’s safe for everyone (men, women, and children, of all ages)
80% of adults are eating 15 hours or longer with about 7 meals/snacks throughout the day
90% of adults are eating for more than 12 hours
Note about keto: we don’t really know the long-term health benefits because it’s difficult to remain on a true ketogenic diet (less than 10% carbs) – the effect on islet cells and blood glucose processing in the pancreas is unknown
A mouse study comparing caloric-restricted mice versus ad libitum showed caloric restriction extended lifespan by 10% longer
Mice on caloric restriction + TRE (eating at night too) lived 10% longer even beyond those who had just caloric restriction
Mice on caloric restriction + TRE without eating at night lived 35% longer in total
Limitations: some mice studies are only in males, which is changing in newer studies
In another study, giving metformin to healthy mice who ate throughout the night induced some aspects of fasting – we haven’t replicated this study in humans
For purpose of weight loss, caloric restriction is the lever – how much you eat matters more than when you eat but consistent timing is important
Debunking a popular study, people in the study were habitually eating in a 10-hour window then were reduced to 8-hour window – you wouldn’t expect much difference in weight loss
Relative energy deficit in sports (REDS): male and female athletes can experience energy deficits if attempting extreme feeding methods like eating just one meal per day or a very short feeding window (e.g., 2 hours)
Female athletes can also experience amenorrhea
Symptoms: depression, anxiety, loss of bone mass
In healthy individuals, 4-hour and 6-hour feeding windows can have positive impacts on weight loss
A study comparing humans on TRE versus 12-hour window but healthier quality both experienced similar weight loss
TRE + low carb diet versus TRE without low carb: studies show the greatest weight loss is in TRE + low carb; both controlled for calories
When caffeine should coincide with breaking fast (and consuming calories)
Acid reflux and heartburn can be exacerbated by consuming caffeine on an empty stomach – black coffee can trigger this
If you’re prone to anxiety or panic attacks, caffeine can exacerbate symptoms – again, consider consuming calories with coffee
Caffeine started as a morning drink to wake up and get on with the day – coffee actually led to the development of breakfast because people wanted something to eat to buffer acid reflux
Circadian aspect of feeding: you can induce metabolic jet lag if you shift your feeding times too much
Consistency is key with TRE feeding times – the cells of the brain and body can be tuned by following food intake times
Saliva production, metabolism, digestive cells, etc. learn to expect food at certain times
When your feeding schedule varies, your body clock is not ready to digest food
The anticipatory signal is critical for optimal digestion
You can have a food hangover if you eat at the wrong time (i.e., late dinner) because the body is not in digestive mode – you may feel physically and cognitively weighed down
Rule of thumb for time change due to travel and daylight saving: For every hour the time is out of rhythm from your norm, it takes the body one day to adjust
“What we do between sunset and bedtime affects most of our health.” – Dr. Satchin Panda
In cultures there is no electricity, and people sleep within 15-30 minutes of sunset
When people go camping, they usually naturally wake shortly after sunrise and sleep shortly after sunset – the melatonin reset from camping can last for weeks
It’s hard to fall asleep with nature because our nighttime activities are partly because we spend more than half of our waking time at work – we don’t really get to express ourselves until the night hours
Some people are more sensitive to light so even in the same household, the same level of light exposure shift one person’s circadian clock but not another
If you are sensitive to light, your body is preparing to fall asleep earlier and melatonin is spiking (unless you combat this with bright light exposure)
Tip: Using a red light (doesn’t have to be anything fancy) can help you fall asleep and stay asleep
Nearly 90% of high school students are chronically sleep-deprived – children and teenagers should sleep 9-10 hours
TRE 12 hours could help children better regulate sleep and wake cycles
Shift workers: broadly defined as staying awake for 2+ hours during habitual sleep time and are engaged in activity – even 1 or 2 days per week can disrupt circadian rhythms and reset the clock
1 in 5 U.S. adults is truly a shift worker for employment, not counting people who experience the lifestyle (e.g., catching up for deadlines, students, new moms, etc.)
In reality, probably 50% of U.S. is on shift working schedule
Almost all digestive diseases are more prevalent among shift workers– ironically, this population is also excluded from most studies
Hidden danger of shift work: many start the day with caffeine and end the day with alcohol (though we see this a lot in the general population as well)
Satchin Panda’s study on shift workers (firefighters) studied 10-hour TRE as a tool for longevity: most could adhere to 5 days; no big difference in weight loss but VLDL levels changed significantly
Those who started with high blood pressure managed blood pressure as much as with medication; similar results with firefighters with high blood sugar (though there aren’t many)
For context, firefighters usually die of cardiovascular disease, not fighting fires
In the future, there will probably be health protocols in the future that center around the hours of sunrise and sunset
Articles
Revival of light signalling in the postmortem mouse and human retina (Nature)
Circadian alignment of early onset caloric restriction promotes longevity in male C57BL/6J mice (Science)
Time-restricted eating with or without low-carbohydrate diet reduces visceral fat and improves metabolic syndrome: A randomized trial (Cell Reports Medicine)
Embers of society: Firelight talk among the Ju/’hoansi Bushmen (Proceedings of the National Academy of Sciences)
Circadian Entrainment to the Natural Light-Dark Cycle across Seasons and the Weekend (Current Biology)
Feasibility of time-restricted eating and impacts on cardiometabolic health in 24-h shift workers: The Healthy Heroes randomized control trial (Cell Metabolism)
Access to Electric Light Is Associated with Shorter Sleep Duration in a Traditionally Hunter-Gatherer Community (Journal of Biological Rhythms)
Daily Eating Patterns and Their Impact on Health and Disease (Trends in Endocrinology and Metabolism)