Why You Should Restrict the Hours You Eat a Day

I don’t like to use the word restrict, but I’m going to in this post … time restricted eating.  We’ve come a long way from the old Food Pyramid when it comes to the field of nutrition. There are so many interesting areas to explore aside from protein, fat and carbs. Obviously the types of foods we eat, as well as the quantity, play an important role in health. But new research is showing that the time we eat as well as number of hours you eat in a day (called time restricted eating)  play a role in health – including your weight, risk of diabetes, heart disease and even cancer. And you probably guessed – most of us eat too many hours in a day. I find this research fascinating and believe that we are only at the tip of iceberg in what we know about it. I’m certainly going to give time restricted eating a try!  I’m going to break this down into 2 blog posts. Here is the first one:

What time you do you take your first bite of food in the morning and your last bite of food at night (yes – even that one bite of ice cream counts)? 50% of people eat within a 15 hr window. So that could mean breakfast at 8 am and your last snack at 11 pm. That’s a lot of eating time! But this isn’t the way our bodies were made to function. Think about how your ancestors ate – maybe within a 6 hour time frame at best. They woke up with the dawn light, searched for food, ate if they were lucky, then went to sleep when the sun set. No Skinny Pop or Halo Top at 10 pm. Studies are showing that our bodies need time without food to perform important functions.

First – a little background on circadian clocks

Time restricted eating research is based on circadian clocks so it helps to have a basic understanding of your clock.

Light and the clock

We all have an internal clock that regulates a wide variety of processes including sleep/wake cycle, metabolism, repair of tissues, secretion of hormones, activation of genes, how active we are and more. Early morning light starts the clock and darkness starts to shut it down. The master clock regulator is deep in the brain. But every organ (i.e. the liver, heart, brain, gastro-intestinal tract) has it’s own clock! Certain processes happen when the clock is turned off and others when it’s turned on. This clock goes haywire in night shift workers because they are up (and eating) with they are supposed to be sleeping. Numerous studies have shown that shift workers have increased rates of obesity, heart disease and cancer in part due to an unhealthy circadian clock.

Food and the clock

Until recently, it was believed light was the only regulator of the circadian clock. But food has also been shown to turn the clock on. The first bite of food in the morning or even cup of coffee with milk (black coffee is debatable!) starts this clock. So if you start eating or drinking at 8 am and have your last bite at 9 pm or later, your clock is running for a long time. This doesn’t give it the time it needs to perform various functions. For example, just the act of eating food and having to metabolize it causes damage in the body by secreting free radicals. The body repairs itself during fasting time – especially fasting at night when you are supposed to be sleeping!

What is time restricted eating (TRE)?

Just like what it sounds – you restrict your eating into a certain time period – usually 8-12 hours in a day. It only refers to the time you eat, not what or how much. So for example, having breakfast at 9 am, dinner at 7 pm (and lunch and snacks whenever you want) would be a 10 hr TRE.

Podcast on time-restricted eating (TRE)

One of my favorite podcasts is Found My Fitness by Rhonda Patrick, PhD. She is a scientist and researcher who talks about REALLY interesting topics and breaks it down for us non-scientist people to understand. To get a better understanding of TRE, I’d recommend that you listen to these 2 fascinating podcasts with her guest Dr. Sachin Panda. Dr. Sachin Panda is a professor at the Salk Institute for biological studies where he researches the circadian clock and does extensive research on TRE. Here are the links to these 2 podcasts as well as the show notes:

1. Time Restricted Feeding and It’s Effect on Obesity, Muscle Mass, Heart Health    

2. Practical Implementation of Time-Restricted Eating & Shift Work Strategies

 3. Show notes for the 2^nd podcast.

Bottom line

In order to function optimally, your body needs more time with its clock turned off.  Dr. Panda’s research has shown that animals that are restricted to eating within a 9 to 12-hour window have improved glucose metabolism, improved lipid profiles, improved cholesterol,  increased lean muscle mass, decreased fat mass, decreased fatty liver, and favorable gene expression patterns.

Stay tuned for my next blog post to learn more about time restricted eating, including studies, tips to get started and how to take part in a research project.