With so many studies giving us different formulas of what we should be eating to achieve fat loss, improve muscle performance, and strive for optimal health, we wind up feeling confused and even disappointed when we don’t get the results we were promised. However, maybe the reason people are getting vastly different results is that many popular approaches only account for what we eat and how much we eat. But what we eat is only a small part of a complete health-promoting diet. In fact, recent studies suggest that it is equally important to consider what we do not eat, how long we do not eat, and when we eat. This is where the ground-breaking research of Time-Restricted Feeding (TRF) comes in.
What Is Time-Restricted Feeding (TRF)?
In new research TRF refers to the practice of eating for only a specific time window each day.
How TRF Works
In their article “Fasting, Circadian Rhythms, and Time-Restricted Feeding in Healthy Lifespan,” from the academic journal Cell Metabolism, Dr. Valter Longo and Dr. Satchidinanda Panda identify the main reasons that regular TRF protocol is beneficial. Namely, our bodies have biological clocks, and we can properly set and achieve a balance between these clocks if we implement TRF principles. These clocks control what we now call circadian rhythms in our bodies. The main clocks for our brains are set by light; however, a “clock” has also been found in the liver, and it is set by our eating habits—but we still want this one to jive with the internal clocks that are set by light.
Many TRF studies have been done on mice, but one study has involved human subjects who were instructed to use a certain app for the study. Another study was done on women who took a national survey. Longo and Panda have analyzed their results and, in their article, discuss the health benefits of fasting and how TRF can affect circadian rhythms (internal body clocks).
First, fasting periods create pleiotropic effects. In other words, genes are affected, and these changes will have multiple effects on traits, which will present themselves.
Valter D. Longo and Satchidananda Panda, “Fasting, Circadian Rhythms, and Time-Restricted Feeding in Healthy Lifespan,” Cell Metabolism 23.6 (2016): 1048‒1059. See also Satoh, Yoko, et al., “Time-Restricted Feeding Entrains Daily Rhythms of Energy Metabolism in Mice,” American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 290.5 (2006): R1276‒R1283.
Fasting-Mimicking Diets (FMD) and TRF are now said to be instrumental in effectively treating several chronic diseases. Chemotherapy and cholesterol-lowering drugs such as statins are described as being less developed than TRF, because changes in eating habits can produce similar results in societal reductions of chronic disease rates with less side effects.
Improved Muscle/Fat Levels and Reduced Risk of Disease
A study involving mice gave one group of mice free rein to eat at any time, and subjected another group to TRF, allowing those mice to eat for only eight hours a day. The two groups of mice ended up with vastly different results. The TRF group had less adiposity (lower fat-to-lean muscle ratio), lower glucose intolerance (carbs are consumed by cells more easily), less leptin resistance (feeling full properly), lower liver pathology (less disease), less inflammation, and increased motor coordination (ran straight longer on a treadmill). As you can imagine, this study has some profound implications on our eating habits as humans. The window of time we eat and the window of time we do not eat directly affect our health in at least a handful of ways. But researchers have discovered yet another practical principle.
Hatori, Megumi, et al., “Time-Restricted Feeding Without Reducing Caloric Intake Prevents Metabolic Diseases in Mice Fed a High-Fat Diet,” Cell Metabolism 15.6 (2012): 848‒860.
TRF and Weekend Cheating
Another mouse study looked at variations in length of eating period and type of diet. Some groups had 8–12-hour TRF windows, while a control group was allowed to eat at any time. The TRF groups showed progressively greater reductions in the harmful effects seen in the group that was given freedom to eat anytime. The study found that even with diets that would otherwise be obesogenic (causing obesity), implementing TRF alone—without restricting total calories—was beneficial! Researchers concluded that TRF is a good therapy for obesity even without restricting calories. Furthermore, this means that even if people were to stop TRF on the weekends (e.g., having a cheat day), they will still reduce their odds of developing metabolic diseases. Overall, TRF reduces the harmful effects of high-fat, high-sucrose, and high-fructose diets. Could TRF be the missing link in a culture that is consumed by health, diet, and exercise fads?
Chaix, Amandine, et al. “Time-Restricted Feeding Is a Preventative and Therapeutic Intervention Against Diverse Nutritional Challenges,” Cell Metabolism 20.6 (2014): 991‒1005.
TRF: Eating Less Without Planning Means Better Sleep and More Energy
A study done on people using a phone app to measure food intake throughout the day showed that on average, more than half of adults in the sample population are eating for 15 hours or longer each day. The same study then looked at a group of eight overweight
individuals and had them eat for only a self-selected 10- to 11-hour period each day for 16 weeks. The results showed a near permanent decrease in body weight over the 16-week period. We can say “permanent” because the benefits were maintained for up to one year, so unlike calorie-restrictive yo-yo diets, the results are real and sustainable.
The group also reported better sleep at night and more alertness during the day. It should be noted, however, that the group also inadvertently ate up to 20 percent less each day (most likely, researchers suggest, because the subjects were given only a small time window to eat). On the other hand, half of the people in the study also ate their last meal after 8 p.m. so they could eat with family, a timing that, according to additional research, is deemed inadvisable. In essence, if humans could commit to a more controlled time window to have all their meals (similar to the mouse studies), they can expect significant health benefits. Taken together, these results strongly suggest that if we exercise control over our feeding time, we can shed excess weight and lower our risk for developing chronic disease.
Shubhroz Gill and Satchidananda Panda, “A Smartphone App Reveals Erratic Diurnal Eating Patterns in Humans That Can Be Modulated for Health Benefits,” Cell Metabolism 22.5 (2015): 789‒798.
National Survey of Women: TRF Associated Reduced Markers of Inflammation
Another study of women participating in the 2009–2010 National Health and Nutrition Examination Survey, showed that eating too much in the evening (specifically between 5 p.m. and 12 a.m.) could increase C-Reactive protein (CRP), which is a risk factor associated with higher rates of breast cancer (and other cancers and diseases). When the amount of food consumed in the evening increased proportionally to the rest of the day, every 10 percent increase was associated with a 3 percent increase in CRP. Conversely, adding an additional meal or snack during the day was associated with an 8 percent reduction in CRP. Furthermore, fasting for longer at night was associated with an 8 percent reduction in CRP for every extra hour of nighttime fasting—but only if the women ate less than 30 percent of their overall daily caloric intake after 5 p.m.
The results show that increasing eating frequency, decreasing evening (5 p.m.–12 a.m.) calories, and having a longer nighttime fasting period might lower any inflammation in the body and thus lower the risk of breast cancer. However, researchers stated that further randomized trials are needed to further validate these associations (more studies need to be done on CRP with respect to other disease).
Marinac, Catherine R., et al. “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.
So Can I Do TRF With My Hectic Schedule?
Having read the comment sections in online literature about TRF, I noticed that some people will say things such as, “I eat before leaving for work at 6 a.m. and don’t get home until 8 p.m. to make a quick dinner, so how can this diet work for me?”
There are two approaches, both of which I have used myself with a similar schedule. The first approach can be physically challenging, and I do not recommend making this switch without a progressive transition:
- Eat a large breakfast at 6 a.m. and then fast all day, not eating again until 8 p.m. That way, if you finish eating your breakfast at 7 a.m., you are creating an 11-hour window of eating and a 13-hour period of fasting.
However, remember that it is also important to eat the majority of your calories earlier in the day, long before your bedtime—namely, while the sun is still in the sky (this is when we are most insulin sensitive, so we absorb nutrients faster rather than store them as fat). So if lifestyle allows it, the following would be an even better strategy:
- Eat first at 6 a.m., eat a big lunch around afternoon, and eat a modest dinner before 6 p.m. In order to be able to have your dinner at 6 p.m., you would have to make dinner the night before, so that you can eat at the designated time. You can then use the time upon getting home (in this case around 8 p.m.) to make food for the next day and then repeat that same cycle indefinitely. Yes, this takes planning ahead, and reheating prepared food is a mild inconvenience, but you will find that this pattern can open up a world of benefits for you, whether it be fat loss, better sleep, etc., and remember that in the morning you can still have a freshly cooked meal; technically, only your supper would be a pre-made/reheated meal.
How TRF Works
- TRF balances circadian rhythms of the body (liver and other organs with the brain).
- TRF will likely result in less calories being consumed, even without calorie reduction being intentional!
- You can expect better-quality, more restorative sleep.
- You will experience Increased energy during the day.
- Other potential benefits:
- less adiposity (lower fat-to-lean muscle ratio)
- higher insulin sensitivity (nutrients are consumed by cells more easily)
- less leptin resistance (feel full properly)
- lower liver pathology (less disease)
- less inflammation
- increased motor coordination (mice ran straight longer on a treadmill)
- Breaking the habit of TRF on the weekend will not negate the benefits.
How to Do It
- Have a 12-hour-or-less eating phase
- Reduce the eating phase more to get equivalently more fat loss (each extra hour will mean more fat loss)
- Eat less of your overall calories between 5 p.m. and 12 a.m. (aim for only one 1/3 as a maximum)
- Add an extra meal or snack in the daytime while keeping the amount of overall daily food consumed the same.
- Increase your nighttime fasting period to experience proportionally increased benefits.
I don’t know about you, but time-restricted feeding is not only intriguing but intuitive. It might end up being the easiest change you can make in your eating habits and yet bring you tangible, sustainable, and desirable benefits! But there is more. Just knowing when to eat in a general sense isn’t all there is to getting your nutrition right. As you will learn, eating certain nutrients at certain times and avoiding other nutrients at certain times makes an additional difference. Make sure to look out for my next article on when to eat eat what types of macronutrients.
Coach Aaron Chin
A BCRPA Registered Personal Trainer For Strength, Conditioning, Mobility, And Healthy Lifestyle Design.