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What you eat determines your health. This probably isn’t news to you. But when you eat? That could be just as important. As it turns out, time-restricted eating (TRE)—eating all your calories in a set time window, for instance within 9 to 12 hours each day—conveys some serious health benefits.

Benefits in Mice and Men

The research is convincing. TRE has been shown to offer both protective and preventive effects against disease, cellular damage, and weight gain. In one lab, two groups of mice were fed identical diets, both unhealthy—a high fat, high sugar, metabolic nightmare, more or less the rodent version of the Standard American Diet.1

The only difference between the two groups of mice was the feeding schedule. One group could eat junk food at their pleasure, a 24-hour, all-you-can-eat smorgasbord. The other group was restricted to eating within a 12-hour feeding window.

Though both groups ate equivalent calories, the time-restricted eating mice stayed healthier than the snack-anytime mice. TRE mice had better glucose tolerance, improved insulin sensitivity, less inflammation, lower body fat, and more.

How do these results translate to humans? As different as we are from rodents, humans also benefit from a shorter feeding window. For instance, athletes on an 8-week TRE schedule showed improved biomarkers and reductions in body fat while maintaining lean muscle mass.2 Women who ate less in the evening (after 5 p.m.), it was found, had lower systemic inflammation and decreased risk for breast cancer.3

There’s more research on the way. Dr. Satchin Panda, one of the authors who devised the mouse experiment, is sponsoring a study called myCircadianClock. His goal is to understand the benefits of TRE on a massive scale. For this project, he’s enlisted thousands of people to track their eating schedules using a phone app. (If you want to learn more, or even be part of the study, go to myCircadianClock.org.)

Considering the benefits you gain, fasting for 12 to 15 hours each night is perhaps the easiest step you can take towards better health. If you chew your last bite of dinner at 7 PM, just wait until 7 AM to start chewing again. Yes, it’s that simple.

Fasting as Cellular Cleanup Time

When you get down to it, there are two main reasons why TRE makes you healthier. The first factor is the hormetic effects of fasting. Hormetic means that a little can be good for you, but a great deal can be harmful. When you forego calories for a few extra hours a day, it stresses your body in a good way. Even after short fasts, cells become more insulin sensitive, markers of inflammation decrease, and body composition improves.4,5

And that’s not all. Along with these advantages, fasting activates cellular repair mechanisms. These processes, in a manner of speaking, clean your body from the inside out.One of these actions, autophagy, allows cells to dispose of and recycle dysfunctional components and damaged proteins. Mitophagy is similar, when mitochondria—your cellular energy centers—clean up intracellular junk. Both of these processes give cells a chance to take out the trash, which promotes healthy aging.

During fasting, DNA, too, can better protect and repair itself, even after sustaining heavy damage. In one study, the DNA in several lucky mice were protected from massive doses of chemotherapythey simply didn’t show as much damage as other mice.6 What was so special about these mice? They had fasted.

Circadian Rhythm Enhancement

Along with fasting, the benefits of TRE are strongly tied to circadian rhythm enhancement. This 24-hour metabolic cycle regulates nearly every function in your body. Your circadian rhythm, explains researcher and podcaster Dr. Rhonda Patrick, controls “everything from making neurotransmitters, to insulin, to glucose transport inside of cells, to oxidizing fatty acids, to repairing damage.”7 About 15 percent of the human genome is beholden to this rhythm.

It’s commonly known that light is the primary circadian governor. Morning light wakes us up, and evening darkness triggers metabolic and hormonal changes that make us
sleepy. Less known is the fact that eating food also impacts the circadian rhythm. That’s right, eating resets secondary clocks in the liver, fat cells, and elsewhere.
8 Hormones like leptin, ghrelin, and melatonin are linked to this daily cycle. These hormones govern sleep, weight regulation, appetite, energy, and more. In other words, they’re important.

A late meal can negatively impact your health. Moonlight munching disrupts your circadian rhythm. One healthy strategy, then, is to eat breakfast with the morning sunlight, allowing your light and food clocks to align to promote proper hormonal and metabolic status.

You Are When You Eat

In the end, TRE offers a remarkably easy strategy for improving our health. By cutting out evening snacks, you’ve got it handled. As for the benefits, you can thank your biology for those. Through complex cellular mechanisms, your body and your health are strengthened by consistent nightly fasts and a robust circadian rhythm.

About the Author

Brian Stanton is a health writer and certified health coach living outside of Philadelphia. When he isn’t practicing yoga or hiking through the woods, he researches the latest science on longevity, sleep, the gut, nutrition, and more. Brian writes on his own blog at www.primalsapien.com.


1 Chaix A, Zarrinpar A, Miu P, Panda S. “Time-restricted Feeding Is a Preventative and Therapeutic Intervention against Diverse Nutritional Challenges.” Cell Metabolism. 20.6 (2014):991-1005. DOI:10.1016/j.cmet.2014.11.001

 2 Moro T, Tinsley G, Bianco A, Marcolin G, Pacelli QF, et al. “Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males.” Journal of Translational Medicine.14 (2016): 290. DOI: 10.1186/s12967-016-1044-0

3 Marinac CR, Sears DD, Natarajan L, Gallo LC, Breen CI, Patterson RE. “Frequency and Circadian Timing of Eating May Influence Biomarkers of Inflammation and Insulin Resistance Associated with Breast Cancer Risk.” PLoS ONE. 10.8 (2015): e0136240. DOI:10.1371/journal.pone.0136240

4 Arnason TG, Bowen MW, Mansell KD. “Effects of Intermittent Fasting on Health Markers in Those with Type 2 Diabetes: A pilot study.” World Journal of Diabetes. 8.4 (2017):154-164. DOI:10.4239/wjd.v8.i4.154

5 Varady KA, Bhutani S, Church EC, Klempel MC. “Short-term Modified Alternate-day Fasting: a Novel Dietary Strategy for Weight Loss and Cardioprotection in Obese Adults.” American Journal of Clinical Nutrition. 90.5 (2009): 1138-1143. DOI: 10.3945/ajcn.2009.28380

6 Tinkum KL, Stemler KM, White LS, Losa AJ, Jeter-Jones S, et al. “Fasting Protects Mice from Lethal DNA Damage by Promoting Small Intestinal Epithelial Stem Cell Survival.” Proceedings of the National Academy of Sciences of the United States of America. 112.5 (2015): E7148-E7154. DOI:10.1073/pnas.1509249112

7 Ferriss T. “Transcript: Dr. Rhonda Patrick on Exploring Smart Drugs, Fasting, and Fat Loss.” The Tim Ferriss Show. 25 May 2017. https://tim.blog/2017/05/25/transcript-dr-rhonda-patrick-on-exploring-smart-drugs-fasting-and-fat-loss/

8 Challet E. “Circadian Clocks, Food Intake, and Metabolism.” Progress in Molecular Biology and Translational Science. 119 (2013): 105-135. DOI: 10.1016/B978-0-12-396971-2.00005-1