A diet guru explains why you should eat dinner at 2 pm

We talk a lot about what to eat, but what about when?

Hermes Rivera / Unsplash
  • A recent study shows that over 50% of people eat over the course of fifteen hours every day.
  • Another study shows that restricting meals to an eight-hour window had profound effects on weight loss.
  • Dr. Jason Fung advocates for earlier dinners in a tighter feeding window.

What you should eat has been the focus of fad diets for decades. Less discussed is when. Thanks to the rise of the ketogenic diet, intermittent fasting has become trendy. Getting into ketosis is possible through a high-fat diet, yet is beneficially aided by fasting. While the science is up for debate on the efficacy of long-term usage of high-fat intake, limiting the duration of your grazing habits seems to have important benefits.

Grazing is one word for it. As nephrologist Dr. Jason Fung, the founder of Intensive Dietary Management Program who specializes in type 2 diabetes and intermittent fasting, points out, one study revealed that the median daily intake of food was 14.75 hours a day.

In fact, over half of the people in that study ate for over 15 hours every day, meaning if they their first meal (or snack) was consumed at 8 am, their last meal wouldn't occur until after 11 pm. These data come from Salk Institute professor Satchin Panda's study, which was tracked by a smartphone app.

Over the course of three weeks, healthy, non-shift workers tracked their eating habits by pressing a button delivered by the app. In total, 26,676 intake events occurred: 22 percent were water, 28 percent pre-packaged food items, and 50 percent mixed meals with multiple items. Another follow-up study tracked participants for sixteen weeks. Less than 25 percent of calories occurred before noon, with 37.5 percent eaten after 6 pm. This is a problem, Fung says.

First off, the least frequent eaters in Panda's study consumed food an average of 3.3 times a day, close to the basic folk wisdom of "three square meals." They only represented 10 percent of the population. That means 90 percent ate more than 3.3 times a day. In fact, many ate a lot more.

Despite what you'll read on holistic blogs everywhere, the type of food was not nearly as relevant as the time that they were actually eating. Fung continues,

When those overweight individuals eating more than 14 hours per day were simply instructed to curtail their eating times to only 10 to 11 hours, they lost weight (average 7.2 lbs, or 3.3 kg) and felt better even though they were not instructed to overtly change when they ate.

Fung cites another study that traced a restricted feeding schedule, known as early Time Restricted Feeding (eTRF). Two groups ate the exact same diet. One consumed their meals between 8 am and 8 pm, while the other chowed down between 8 am and 2 pm. All volunteers in this study were pre-diabetic.

The benefits were huge. Mean insulin levels dropped significantly, and insulin resistance dropped as well. Insulin is a driver of obesity, so merely changing the meal timing and restricting the number of hours you ate, and also by moving to an earlier eating schedule, produced huge benefits even in the same person eating the same meals. That's astounding. Even more remarkable was that even after the washout period of seven weeks, the eTRF group maintained lower insulin levels at baseline. The benefits were maintained even after stopping the time restriction. Blood pressure dropped as well.

Fung notes that green tea is an important tool in helping those trying to fast.

rawpixel / Unsplash

Fung argues that while it's not actually difficult to fast for sixteen or eighteen hours a day—I concur, having tried it for two months; your body quickly adjusts—eating dinner at 2 pm presents a serious challenge to the way our society is structured.

What Fung is really interested in is changing the narrative around diet. Sure, too much sugar is not good; fresh produce and whole grains are most often a better decision than processed foodstuffs littered with preservatives. Not every body can handle too much caffeine, which affects sleeping patterns, which affects metabolism, which leads to obesity. Nuance is important.

Fung is advocating is for a broader discussion of when. Given all we've been learning about the importance of circadian rhythm (which can now be measured in our your blood), we're discovering that even a few hours of fasting a day can have profound consequences. Magical elixirs might not help you lose weight, but deciding not to drink them just might.

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Stay in touch with Derek on Twitter and Facebook.

Yug, age 7, and Alia, age 10, both entered Let Grow's "Independence Challenge" essay contest.

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The surprise reason sleep-deprivation kills lies in the gut

New research establishes an unexpected connection.

Reactive oxygen species (ROS) accumulate in the gut of sleep-deprived fruit flies, one (left), seven (center) and ten (right) days without sleep.

Image source: Vaccaro et al, 2020/Harvard Medical School
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  • Surprisingly, the direct cause seems to be a buildup of Reactive Oxygen Species in the gut produced by sleeplessness.
  • When the buildup is neutralized, a normal lifespan is restored.

We don't have to tell you what it feels like when you don't get enough sleep. A night or two of that can be miserable; long-term sleeplessness is out-and-out debilitating. Though we know from personal experience that we need sleep — our cognitive, metabolic, cardiovascular, and immune functioning depend on it — a lack of it does more than just make you feel like you want to die. It can actually kill you, according to study of rats published in 1989. But why?

A new study answers that question, and in an unexpected way. It appears that the sleeplessness/death connection has nothing to do with the brain or nervous system as many have assumed — it happens in your gut. Equally amazing, the study's authors were able to reverse the ill effects with antioxidants.

The study, from researchers at Harvard Medical School (HMS), is published in the journal Cell.

An unexpected culprit

The new research examines the mechanisms at play in sleep-deprived fruit flies and in mice — long-term sleep-deprivation experiments with humans are considered ethically iffy.

What the scientists found is that death from sleep deprivation is always preceded by a buildup of Reactive Oxygen Species (ROS) in the gut. These are not, as their name implies, living organisms. ROS are reactive molecules that are part of the immune system's response to invading microbes, and recent research suggests they're paradoxically key players in normal cell signal transduction and cell cycling as well. However, having an excess of ROS leads to oxidative stress, which is linked to "macromolecular damage and is implicated in various disease states such as atherosclerosis, diabetes, cancer, neurodegeneration, and aging." To prevent this, cellular defenses typically maintain a balance between ROS production and removal.

"We took an unbiased approach and searched throughout the body for indicators of damage from sleep deprivation," says senior study author Dragana Rogulja, admitting, "We were surprised to find it was the gut that plays a key role in causing death." The accumulation occurred in both sleep-deprived fruit flies and mice.

"Even more surprising," Rogulja recalls, "we found that premature death could be prevented. Each morning, we would all gather around to look at the flies, with disbelief to be honest. What we saw is that every time we could neutralize ROS in the gut, we could rescue the flies." Fruit flies given any of 11 antioxidant compounds — including melatonin, lipoic acid and NAD — that neutralize ROS buildups remained active and lived a normal length of time in spite of sleep deprivation. (The researchers note that these antioxidants did not extend the lifespans of non-sleep deprived control subjects.)

fly with thought bubble that says "What? I'm awake!"

Image source: Tomasz Klejdysz/Shutterstock/Big Think

The experiments

The study's tests were managed by co-first authors Alexandra Vaccaro and Yosef Kaplan Dor, both research fellows at HMS.

You may wonder how you compel a fruit fly to sleep, or for that matter, how you keep one awake. The researchers ascertained that fruit flies doze off in response to being shaken, and thus were the control subjects induced to snooze in their individual, warmed tubes. Each subject occupied its own 29 °C (84F) tube.

For their sleepless cohort, fruit flies were genetically manipulated to express a heat-sensitive protein in specific neurons. These neurons are known to suppress sleep, and did so — the fruit flies' activity levels, or lack thereof, were tracked using infrared beams.

Starting at Day 10 of sleep deprivation, fruit flies began dying, with all of them dead by Day 20. Control flies lived up to 40 days.

The scientists sought out markers that would indicate cell damage in their sleepless subjects. They saw no difference in brain tissue and elsewhere between the well-rested and sleep-deprived fruit flies, with the exception of one fruit fly.

However, in the guts of sleep-deprived fruit flies was a massive accumulation of ROS, which peaked around Day 10. Says Vaccaro, "We found that sleep-deprived flies were dying at the same pace, every time, and when we looked at markers of cell damage and death, the one tissue that really stood out was the gut." She adds, "I remember when we did the first experiment, you could immediately tell under the microscope that there was a striking difference. That almost never happens in lab research."

The experiments were repeated with mice who were gently kept awake for five days. Again, ROS built up over time in their small and large intestines but nowhere else.

As noted above, the administering of antioxidants alleviated the effect of the ROS buildup. In addition, flies that were modified to overproduce gut antioxidant enzymes were found to be immune to the damaging effects of sleep deprivation.

The research leaves some important questions unanswered. Says Kaplan Dor, "We still don't know why sleep loss causes ROS accumulation in the gut, and why this is lethal." He hypothesizes, "Sleep deprivation could directly affect the gut, but the trigger may also originate in the brain. Similarly, death could be due to damage in the gut or because high levels of ROS have systemic effects, or some combination of these."

The HMS researchers are now investigating the chemical pathways by which sleep-deprivation triggers the ROS buildup, and the means by which the ROS wreak cell havoc.

"We need to understand the biology of how sleep deprivation damages the body so that we can find ways to prevent this harm," says Rogulja.

Referring to the value of this study to humans, she notes,"So many of us are chronically sleep deprived. Even if we know staying up late every night is bad, we still do it. We believe we've identified a central issue that, when eliminated, allows for survival without sleep, at least in fruit flies."

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