
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.