Your Guide to Time-Restricted Eating

Our bodies were designed to thrive when we eat, fast and rest timed with our circadian rhythms.

Intermittent fasting improves body composition, cognitive function, heart health, and the immune system. But there’s another type of intermittent fasting called time-restricted eating, or TRE, that can have an even more profound influence on different areas of your health.

TRE was popularized by the research of Dr. Satchin Panda, author of The Circadian Code. Panda found that the body’s cellular clocks are responsible for much of our health and wellbeing and that habits like eating too frequently or too late can disrupt those clocks, affecting our weight, health, and sleep.

So where standard intermittent fasts only focus on how long an eating window is – usually somewhere between four to twelve hours – time-restricted eating is about when that window starts. The earlier, the better.

What is Time-Restricted Eating?

While often lumped in with other forms of intermittent fasting, time-restricted eating (TRE) is its own separate philosophy that aligns mealtimes with your natural circadian rhythm. TRE encourages you to eat the majority of your meals as early as possible, and rarely ever in the evening.

Not eating at night might sound like the death knell to your social life and happiness. But there’s good news: research has shown that the benefits of time-restricted eating are maintained even with two ‘cheat days’ per week. So you get to have your cake and eat it as late as you please – two nights out of the week, that is.

Whether you fast for 12, 16, or 20 hours a day, if you want to practice TRE, all you have to do is start and break your fast earlier.

Benefits of Time-Restricted Eating

Metabolic syndrome/diabetes

TRE has been known to reduce markers of metabolic syndrome in both animals and humans. A more recent trial of 19 people indicates that time-restricted eating, along with standard drug treatments, improves cardiometabolic health. Bodyweight, waist size, blood sugar, cholesterol, and blood pressure all went down when participants ate their meals within a ten-hour window.

Weight loss

Even though TRE study participants are allowed to eat as much as they want, the trend is that people still eat fewer calories. This almost always leads to weight loss. In a 2019 study, participants who fasted from 8:00 am to 2:00 pm reported lower levels of hunger, more fullness, and were tested to have lower levels of the hunger hormone ghrelin than those who ate in the evening. The decrease in appetite was thought to be the cause of weight loss.

Maintain muscle mass while slimming down

One of the main problems with dieting is that you typically can’t consume enough calories to support muscle. (Studies show that yo-yo dieters are far likelier to have low muscle mass, compared to people who maintain their weight.) But several studies show that lean muscle mass is preserved in experienced weight lifters who practiced time-restricted eating – both male and female.

Longevity

Time-restricted eating has been demonstrated to increase lifespan in rodents. But though larger and more extensive trials are necessary, there’s good evidence that TRE may lead to longer lives in humans, too. A small study done on 11 participants showed that several longevity genes were upregulated within a week of time-restricted eating. Longevity markers such as autophagy were improved by TRE as well.

Sleep

Improved sleep is one of the most commonly reported improvements in people experimenting with time-restricted eating. This is because eating food later in the day signals to your body’s peripheral circadian clocks that it’s time to be awake, which prevents your brain from falling and staying asleep like normal. Once you eliminate the nighttime eating, your brain won’t argue with your body when it’s time for bed.

Risks of Time-Restricted Eating

The health risks of TRE are nominal. As with most fasting methods, slight symptoms including headaches, hunger, dizziness, and fatigue can be expected. That said, people with hypoglycemia could experience severe blood sugar crashes while fasting, and those with liver or kidney issues should avoid extended periods of fasting.

Make sure to check with your doctor before attempting any time-restricted eating regimen.

How to Do Time-Restricted Eating

To begin, doctors recommend committing to at least one month of TRE to see long-term benefits. Once you’ve decided how long you’ll try it, you’ll need to determine an eating window that’s right for you.

Common TRE schedules include 7:00 am to 7:00 pm, 7:00 am to 5:00 pm, 10:00 am to 6:00 pm, and 8:00 pm to 4:00 pm.

Beginners may need a longer eating window of 12 hours. If you have more experience with fasting, you can set an 8-hour eating window. But no matter how long your window is, make sure to break your fast early and to have dinner early. (Most people will break their fasts by 10:00 am, but you can start eating as early as you want to.)

Here are some helpful tips to stick with your eating windows:

• If you’re hungry before you’ve hit your eating window, drink coffee or tea.
• Do some light exercise first thing in the morning to kickstart your metabolism and increase insulin sensitivity.
• Aim for several minutes of bright light exposure each morning to bolster your circadian clock. (This will help you feel less hungry in the evening.)
• Try an ounce of apple cider vinegar (ACV) in a glass of water if you’re feeling hungry before bed. Don’t have ACV? Just drink the water, then.
• When watching TV, make sure to have something enjoyable but calorie-free to take the place of snacks. (Sparkling water, tea, etc.)