Time-Restricted Feeding and Its Effects on Obesity, Muscle Mass & Heart Health

‪LISTEN

Dr. Satchin Panda is a professor at the Salk Institute for biological studies

Where he researches the circadian clock

What is the circadian clock and why it’s so important?

• It is based on the changing environment of light during a day.
• It’s particularly important for diurnal animals:
  • Dictates when to go to sleep and wake up.
  • Evolved from pressure and anticipation.
• Every organ has its biological clock.
• Its performance varies during the day.
• Babies also have clocks, but they aren’t tied to outside light until 6 months.
• Today’s top diseases are chronic.
  • They can be caused by an unhealthy circadian clock.

How is it related to our metabolism?

• After many experiments on rodent’s brain
  • Scientists found the Suprachiasmatic Nucleus (SCN) located in the hypothalamus
• Without it, we would have no sense of time.
• It synchronises organs to activate during certain times.
• What happens in the case of neurodegenerative diseases?
  • The SCN is damaged by the degeneration.
  • People lose their internal clock.
  • The hippocampus, which is in charge of long-term memory, is affected.

The importance of light

• Light can reset our internal clock.
  • It adapts when seasons change and when we travel in other time zones.
• Why is it blind people can’t see, but still have a clock?
  • Scientist found that if the eyes are taken, they loose their clock.
  • They discovered melanopsin, a photoreceptor, in the ganglion cells, located in the eyes.
  • These photoreceptors are connected to our SCN.
  • They are sensitive to BRIGHT light and TIME of exposure (10 000 Lux during several minutes).
• Melanopsin also regulates sleep and our mood.
  • It suppresses melatonin, a sleeping hormone.
  • Melatonin they builds up during the day as the light decreases, making us sleepy when night comes.
  • When the sky is gray/there’s no light it can cause sessional depression.
  • We need more light in the first half of the day and less after noon.
  • Melanopsin promotes cortisol, an hormone that makes us more alert (stress hormone)
  • Therefore, cortisol spikes early in the morning and decreases throughout the day.
  • Leading a stressful life maintains our level of cortisol high, which can lead to health issues.

The role electronics play in our internal clocks

• Blue light from screens and lighting send the wrong signal to the SCN.
• Melatonin can’t build up.
  • So, someone would have trouble sleep or would wake up tired.
• Philips Hue: Lights that can be programmed to send red lights instead of blue.
• F.lux: Application that filters blue light and sends different shades depending on the time of day.

What about Jet Lag and night workers?

• People that switch from a day shift to a night shift:
  • They sleep during the brightest sunlight exposure.
  • They rarely get exposed to the natural light.
• While light does half of the work, the other half is done by food.
• When traveling, light and food habits change, which messes up our SCN.

How food regulates our tissues

• Internal clocks are like traffic lights: without the right timing, it creates accidents and traffic jams.
• There’s a specific time for every metabolic activity.
• If not properly adjusted:
  • There’s build up of undesired by-products.
  • It puts stress on our cells.
  • It can lead to many chronic diseases.
• Our organ’s clocks respond to when we eat.
  • The act of eating turns on the genes responsible for digestion.
  • Light has little impact in that case.

The principle behind time-restricting feeding

• The idea is to restrict your eating into a certain period of time, usually being12h.
• Mice that don’t have a circadian clock have greater chances of developing a metabolic disorder such as:
  • Obesity
  • Cardiovascular diseases
  • Diabetes
  • Cancer
• High fat diet and high sugar diet were tested with time-restriction.
  • Did not matter WHAT or HOW MUCH you eat but WHEN you eat is crucial.
  • Mice ate the same food but the ones on time-restriction had 28% less body mass and 70% less fat.
• Time restricting has a huge impact on our body.
• Nutrition or quality of food still matters.
• The program increased lean mass.
  • This can be caused by an increase in Nicotimamide Ribose, which creates more NAD.
  • More NAD gives more ATP.
  • ATP, being the main energy source of our body, boosts our energy level.
• Restricting in an 8h to 9h period is even more beneficial.
  • It increases endurance.
  • An increase in brown fat tissue was noted.
  • There’s also an increase in mitochondria activity.

Intermittent fasting versus time-restricting feeding

• In both cases, there’s a prolonged fasting period.
• When we eat, we damage our cells.
• Fasting promotes repairs.
• Intermittent fasting restricts calories, time-restricting does not.
• It’s a comeback to our primordial physiology.
• The two methods are in synch with the circadian clock.
• Melatonin receptors were found in pancreas.
  • The increase of melatonin that happens during the day inhibits insulin production.
  • Therefore, late night calories have different effect on our health.
• mycircadianclock.org
  • This site is a nutrition study application.
  • 50% of the population eat throughout a period of 15 hours.
  • 8 people that were asked to restrict their time.
    • They lost 4% body weight.
    • They slept better and were more energetic in the morning.
  • It’s an indirect way to reduce calories and eat better.
  • It contains two phases:
    • Phase 1: Collect how much and when people eat, sleep, exercise.
    • Phase 2: Selecting a program to follow.
  • It can be synched with the Health Kit and Google Fit application, which measure movement.
• It’s a simple life style changes.
• Experiments on fruit flies showed:
  • Their heart has similar genes and diseases as humans.
  • By following a time-restricted diet, they develop heart problem later.
  • They slept better and were more energetic.
  • The mitochondria in the heart cells were healthier.
  • The Electron Transport Chain (ETC) was more effective.
  • It also showed better proteostasis, which is important for protein folding.

Links to microbiota and digestion

• Our microbiota also follows a circadian clock.
• Different bacteria are active during different part of the day.
• Regularity between fasting and eating allows a vast variety of species to grow.
• Time-restricting changes the way sugar are digested.
• It can also decrease our cholesterol level and increase the production of bile acid.
• uBiome: a website where you can evaluate the changes in your gut bacteria.