July 11, 2016

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

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.