Late Dinners Make You Sicker? A Case for Breakfast and Early Time-Restricted Feeding
A new intermittent fasting study suggests that eating all of your daily calories before 3 PM might improve your metabolic health, especially if you struggle with blood sugar control.
All of the breakfast skippers out there, whether they realize it or not, are naturally practicing intermittent fasting. They may reap many of the benefits of a form of fasting called time-restricted feeding, including better weight control, improved blood sugar control, potentially lowered lipid levels and reduced levels of inflammation.
But breakfast skipping is controversial for a reason. Skipping breakfast may lead people to eat the majority of their calories late in the day, or after 4 PM. Eating late in the day runs counter to signals the brain sends to various tissues in the body to slow down metabolism in preparation for sleep. Think of it like this: Late dinners cause you to experience something akin to jetlag!
To Breakfast, or Not to Breakfast?
While breakfast skippers may glean some of the benefits of intermittent fasting, they also may get some of the drawbacks of eating out of tune with their biological clocks.
A new pilot study published in Cell Metabolism suggests that eating during a narrow window early in the day, in other words eating all of your calories before 3 PM, may substantially improve blood sugar control and insulin sensitivity as well as lower blood pressure and biomarkers of oxidative stress.
“I don’t think we’ve nailed the breakfast question down because whether skipping breakfast improves your metabolic health or not may largely depend on what and when you are eating the rest of the day, especially at dinner,” said Dr. Courtney Peterson, an assistant professor in the department of nutrition sciences at the University of Alabama at Birmingham and corresponding author of the study.
Peterson’s study is the first human trial of early time-restricted feeding. This meal timing strategy combines intermittent fasting (14 or more hours of daily fasting) with eating in alignment with the circadian clock. It is tantamount to eating dinner by early afternoon. Think of hearty breakfast at 7am, lunch at 10am and dinner at 1pm (it might require bringing meals to work and working through lunch!) Peterson is investigating how meal timing affects rhythms in circadian clock genes and molecular mediators associated with fasting.
Eating ‘Till the Sun Goes Down
“I got interested in intermittent fasting as a research topic about eight years ago,” Peterson said. “I was fascinated by this idea of alternating periods of eating and fasting. There are many approaches to fasting — Dr. Krista Varady’s research has looked at the impacts of fasting or eat very few calories some number of days per week. But I started thinking, it would be more practical to do this every day and not have to think about it as much, for example by moving dinner earlier in the day or moving breakfast later.”
In 2012, Peterson saw a research study published by Dr. Satchidananda Panda and colleagues at the Salk Institute for Biological Studies demonstrating the benefits of time-restricted feeding, a form of intermittent fasting that involves eating during a narrow window in the day, in mice.
“He compared mice that grazed throughout the day to mice that ate for 8 hours and were fasted for 16 hours each day,” Peterson said. “Dr. Panda did an interesting thing in the study — he had rodents in both the grazing group and the time-restricted feeding group eat the exact same amount of food, on a high fat diet, each day. Amazingly, the rodents that ate the high-fat diet and grazed throughout the day quickly developed diabetes, hypertension, high cholesterol levels and high levels of inflammation. But rodents that ate the exact same food in a narrower eight-hour period gained significantly less weight, had lower cholesterol levels, lower levels of inflammation and greater blood sugar control. They even had the human equivalent of greater athletic performance! The mice on a time-restricted feeding schedule were healthier and had lower levels of fat in their livers. I was amazed at the results. I thought, wow, it would be fantastic if this worked in humans.”
Many findings in animals don’t translate to impact in humans. But shortly after Panda’s paper on time-restricted feeding in mice appeared in Cell Metabolism, Oren Froy and colleagues published a study in Obesity on the impact in humans of high caloric intake at breakfast versus dinner. Peterson took note.
“Froy’s research was basically investigating the old adage of eating breakfast like a king, lunch like a prince and dinner like a pauper,” Peterson said. “The group has conducted a handful of trials in humans since, but that first study found that overweight women who followed the strategy of eating a large breakfast and a small dinner lost significantly more weight than those who ate the same meals in the opposite order. What was amazing to me was that within the first few weeks of the intervention, the researchers were already seeing significant improvements in blood sugar control. Not only that, but the women who were eating most of their calories early in the day, even though they were losing more weight, were less hungry. Losing more weight and feeling less hungry than people struggling to lose weight — that seemed phenomenal!”
Breakfast is the New Dinner.
When researchers talk about time-restricted feeding, they are usually referring to restricting caloric intake to a narrow window during the day. Peterson decided to take this idea to the extreme and combine it with what we now know about circadian rhythms. She set out to investigate how time-restricted feeding done very early in the day might impact weight, metabolic health and hunger in humans.
“I thought with early time-restricted feeding we might get the benefits not only of time-restricted feeding, but of timing meals with our circadian rhythms,” Peterson said.
Intermittent fasting is generally associated with improved blood sugar control, lowered blood pressure and increased fat oxidation or fat burning. Intermittent fasting has also been shown to reduce oxidative stress. But how much are the benefits of intermittent fasting associated with meal timing throughout the day? According to Peterson, intermittent fasting carried out at the “wrong” time of day, such as fasting through breakfast and lunch and eating late into the day, might even be detrimental, especially in terms of insulin sensitivity and inflammation.
“I currently recommend that people eat most of their calories early to mid-day,” Peterson said.
The 2017 Nobel Prize in Physiology or Medicine was awarded to Jeffrey C. Hall, Michael Rosbash and Michael W. Young for their discoveries of molecular mechanisms that control circadian rhythms, or rhythms that control physiology, metabolism and behavior that are driven by our biological clock. This clock is set by our exposure to bright light throughout the day… but also by our exposure to nutrients — food!
“What we’ve learned about our circadian rhythms is that we are better able to do certain things during certain times of day,” Peterson said. “For instance, we perform better at sports in the afternoon, we sleep better in the evening when our melatonin levels are higher, and you have your highest blood pressure rise in the morning, which is why we see more heart attacks happening in the morning. But we also know that our blood sugar control is better in the morning.”
If you were to eat the same meal for breakfast, lunch and dinner, according to Peterson, your blood sugar levels would spike much higher at lunch and substantially higher at dinner. The effect is remarkable, and researchers have known about it now for several decades. But they haven’t understood why blood sugar control changes throughout the day until recently.
“We are starting to put metabolism together with our knowledge of circadian rhythms, and we are starting to understand that there are very strong consequences to the times of day that we eat, sleep and exercise,” Peterson said.
The Brain and Body Disconnect — Split Across Time Zones?
Peterson and colleagues at the Pennington Biomedical Research Center in Louisiana are the first to rigorously look at the impacts of early time-restricted feeding in humans. The reasoning behind their latest study in Cell Metabolism is that eating out of tune with your body’s master biological clock can have negative consequences on metabolism and tissue function, including how well your muscles, liver and fat tissues burn sugars.
The brain’s clock, the suprachiasmatic nucleus in the hypothalamus in the brain, is set by sunlight or bright light exposure. But it turns out that different tissues and organs in the body each have their own mini biological clocks that are set by a variety of factors including nutrient signaling, or the food you eat. If you eat late at night, your brain is telling your muscles, liver and fat to slow their metabolism down while these tissues are getting conflicting nutrient signals to rev up. It’s like an orchestra, but where everyone is out of time and tune with one another. These mixed signals wreak havoc on the body’s metabolism and its ability to control blood sugar or switch easily between burning fats and sugars.
In short, just as it is best to get the majority of your sunlight exposure early in the day (before 2 or 3 PM) to allow your melatonin levels to rise in time for bedtime, it may be best to eat the majority of your daily calories early in the day or before the typical American dinner. In fact, getting late bright light exposure can worsen your blood sugar control, and eating late can negatively impact your sleep patterns!
Dinner of Champions
Peterson says that dinner may actually be the most important meal of the day. Our bodies are most vulnerable to junk food or sugar spikes in the evening, making it even more important to eat a healthy, and early, dinner.
She has data to back this up. Peterson and colleagues found that prediabetic men following a form of intermittent fasting called early time-restricted feeding substantially improved their insulin sensitivity, blood pressure and oxidative stress levels as compared to men eating the same meals on a 12-hour eating schedule. Moreover, men on an eTRF schedule experienced these metabolic health improvements without losing weight.
Peterson set out to discover whether time-restricted feeding has intrinsic benefits. To do this, she had to strictly control what and when research participants ate, to make sure that the benefits of time-restricted feeding in these participants weren’t in fact simply the benefits of eating less food. She recruited research volunteers, 8 prediabetic men, for a rigorous controlled feeding trial.
“We made all of their food for them for five weeks and then we required that they eat the food under supervision, either in our clinic or on Skype,” Peterson said. “We also made sure that we fed them enough such that they didn’t lose weight, so that we could study the impacts of intermittent fasting independent of weight loss. These are intense studies that are difficult to pull off. This was actually the first controlled feeding trial of any type of intermittent fasting in humans.”
In the study, all men on an intermittent fasting schedule started eating around 8 AM finished dinner by 3 PM. The men in the control group ate the exact same meals, but over a 12-hour period.
Men with prediabetes were randomized to early time restricted feeding (eTRF, 6-hr feeding period, with dinner before 3 p.m.) or a control schedule (12-hr feeding period) for 5 weeks and later crossed over to the other schedule. eTRF improved insulin sensitivity, b cell responsiveness, blood pressure, oxidative stress, and appetite. We demonstrate for the first time in humans that eTRF improves some aspects of cardiometabolic health and that IF’s effects are not solely due to weight loss. — Sutton et al., 2018
Peterson found that prediabetic men on the early time-restricted feeding schedule experienced improved insulin sensitivity, or ability to process sugar in the bloodstream. One of the first metabolic health changes in individuals with prediabetes and diabetes is insulin insensitivity, which can have many negative downstream consequences. The men on the early time-restricted feeding schedule also experienced dramatic lowering of blood pressure, around 10 to 11 points on average, and reduced oxidative stress, measured in terms of damaged fat molecules known to cause atherosclerosis and heart disease.
“That was really exciting to see, because that extent blood pressure lowering is about what you would see with a medication such as an ACE inhibitor — and we didn’t even have anyone lose weight,” Peterson said.
In Peterson’s study, fasting men’s triglyceride levels went up, although this could just be because Peterson’s group only measured triglyceride levels in the morning before breakfast, after men who were fasting had already gone a much longer time without calories (18 hours or so) than men on a control meal schedule. Triglyceride levels can rise over time while fasting, due to fat burning.
Overall, Peterson is excited by the results of her first pilot study on early time-restricted feeding. She plans to investigate this form of intermittent fasting in future studies with larger numbers of research participants, both men and women. In these studies, she plans to measure biomarkers of metabolic health such as blood sugar control and lipid levels at multiple timepoints through fasting and feeding periods, to better understand daily fluctuations in both participants who practice early time-restricted feeding and participants who don’t. She also is planning a study to investigate if intermittent fasting can actually help people lose more fat and less muscle than standard caloric restriction.
Our trial tested eTRF [early time-restricted feeding] in men with prediabetes — a population at great risk of developing diabetes — and indicates that eTRF is an efficacious strategy for treating both prediabetes and likely also prehypertension. We speculate that eTRF — by virtue of combining daily intermittent fasting and eating in alignment with circadian rhythms in metabolism — will prove to be a particularly efficacious form of IF [intermittent fasting]. — Sutton et al. 2018
Time-restricted feeding studies are more complicated to conduct with female research participants, it turns out. Women’s blood sugar control and fat burning varies throughout the month based on their menstrual cycle, meaning that researchers studying fasting in women need to match metabolic health and biomarker measurements for different research participants with the participants’ menstrual cycles. In future studies, however, Peterson will study early time-restricted feeding in both men and women and account for these fluctuations.
“As a woman, I’m super sympathetic to the need for more studies of time-restricted feeding in female research participants,” Peterson said.
Skip a Dinner, Lose the Late-Night Cravings
Today, Peterson herself avidly practices early time-restricted eating. On week days she tries to eat all of her calories before 2 PM. She gives herself a break on the weekends in order to enjoy family dinners.
“I try not to stress about it. If I go to dinner with friends, I’ll eat with them, even if it’s something light,” Peterson said. “I focus mostly on eating healthy.”
The good news for dinner skippers is that there is evidence that you don’t need to practice this early time-restricted feeding every day of the week to glean its benefits — practicing this eating schedule five out of seven days per week is nearly as effective as practicing it every day.
Peterson says that one of the most surprising findings from her study was that participants who ate on an early time-restricted feeding schedule reported being less hungry in the evenings than they did on a normal eating schedule.
“Most people I talk to can’t believe this,” Peterson said. “But if you’ve eaten the majority of your calories early in the day, your body is smart, it doesn’t forget that. Your body remembers all of those calories you ate, and you don’t feel as hungry.”
The typical American eating schedule, in which many people don’t get enough calories early in the day, sets people up for being hungrier and potentially binging in the evenings when their blood sugar control is worse, Peterson says.
Fast Forward for LIFE: Skip a Dinner for Health, Pay it Forward
Convinced to try skipping dinner for metabolic health? As you do, consider paying health forward by donating a meal to someone in need with the LIFE Fasting Tracker #FastForward4LIFE food drive with Gleaners Food Bank. Find the “fast forward” heart icon in the LIFE Fasting Tracker app to fast and donate today (ahem… tonight)!
Peterson is an assistant professor in the department of nutrition sciences at the University of Alabama at Birmingham. She has received The Obesity Society’s Early Career Research Grant, and she holds a Ph.D. in physics from Harvard University and four Master’s degrees. Her research interests include meal timing, circadian rhythms, intermittent fasting, diet quality and mathematical modeling of metabolism and body composition. The overarching goal of her research is to develop novel dietary interventions to prevent, treat or reverse type 2 diabetes, cardiovascular disease and obesity.