Reference
Sutton EF, Beyl R, Early KS, Cefalu WT, Ravussin E, Peterson CM. Early time-restricted feeding improves insulin sensitivity, blood pressure, and oxidative stress even without weight loss in men with prediabetes. Cell Metab. 2018;27:1212-1221.
Design
A 5-week, randomized, crossover, isocaloric, and eucaloric controlled feeding trial testing early time-restricted feeding (eTRF) in men with prediabetes. In brief, participants adopted an eTRF schedule (6-hour daily eating period, with dinner before 3:00 pm) and a control schedule (12-hour eating period) for 5 weeks each, separated by a washout period of approximately 7 weeks.
Objective
To determine if a supervised controlled feeding trial has benefits for cardiometabolic health independent of weight loss.
Participants
All meals eaten by participants during the course of the study were prepared by study staff. Participation was limited by the strict nature of the 6-hour eating schedule for 5 weeks. Of the 934 individuals who applied to participate in this trial, 130 were screened in the clinic and just 15 met all eligibility requirements. Twelve men were enrolled and 8 completed the trial; mean age was 56, and all participants were overweight (mean BMI 32.2) and prediabetic (fasting glucose 102 mg dL).
Intervention
The men were fed 3 meals per day. Participants chose a time between 6:30 am and 8:30 am to eat breakfast every day, and lunch and dinner were timed accordingly. For example, participants in the eTRF arm who ate breakfast at 7:00 am ate lunch at 10:00 am and dinner at 1:00 pm; those in the control arm who ate breakfast at 7:00 am ate lunch at 1:00 pm and dinner at 7:00 pm. During the intervention phases of the study, participants ate only food provided by study staff, were fed enough food to maintain their weight, and ate all meals while being monitored by study staff.
Outcome Measures
Primary endpoints were glucose tolerance, postprandial insulin, and insulin sensitivity as measured using a 3-hour oral glucose tolerance test (OGTT). Secondary endpoints were cardiovascular risk factors and markers of inflammation and oxidative stress. Metabolic hormones were added later as an exploratory outcome. Differences between meal timing schedules were assessed by comparing the 2 within-arm changes against each other; these treatment effects are denoted by D.
Key Findings
Early time-restricted feeding improved insulin sensitivity, pancreatic beta cell responsiveness, blood pressure, oxidative stress, and appetite. This study demonstrated for the first time in humans that eTRF improves some aspects of cardiometabolic health and that intermittent fasting’s effects are not solely due to weight loss.
Practice Implications
We may need to rethink our use of the phrase “You are what you eat” and amend it to something like “You are when you eat.” More and more it seems that choices of what we eat have less impact on health than the decisions of when we eat it. In recent years we have seen multiple published studies on caloric restriction and intermittent fasting and, of late, studies that look at meal timing.
It now appears that our internal circadian clocks modulate energy balance and metabolism and that calories are used more efficiently in the morning than in the evening.
Intermittent fasting (IF), that is, alternating periods of eating and fasting, appears to improve multiple metabolic abnormalities in rodent research. These improvements appear to be distinct from what might occur simply from weight loss secondary to caloric restriction. Repeated prolonged intervals of fasting trigger shifts in physiology and morphology that do not occur with basic weight loss.1 Human trials on IF began about 10 years ago, in particular studies on alternate day fasting.2 Then came alternate day modified fasting (ADMF),3 and what became known as the 5:2 diet, in which calories were restricted 2 days out of the week.4
In most of these regimens, participants couldn’t eat enough calories and invariably lost weight. It has been impossible to determine whether the observed benefits were due to weight loss or the periods of fasting. This study demonstrates that, at least in the case of prediabetes, it is the fasting periods that trigger the shifts in function. In this study the researchers worked hard to maintain the body weight of participants.
Looking at an example daily meal menu (Figure 1), one feels some empathy for those in the ETRf arm—they were required to consume 3 hearty meals before mid-afternoon.
Figure 1. Menu for participants in early time-restricted feeding study
| Breakfast | Oatmeal Scrambled egg whites 1% milk Butter Grape juice Graham crackers Peanut butter |
| Lunch | Hamburger bun Grilled chicken breast Lettuce Tomatoes Mayo & mustard Fruit salad Yogurt (strawberry) *Cheese crackers |
| Dinner | Catfish almondine Rice pilaf Green beans Butter Dinner roll, wheat Peaches 1% milk |
*Food was or was not served, depending on participant’s calorie level
The normal pattern of food consumption in the United States is to eat lightly in the morning, moderately at lunch, and then consume the majority of the day’s calories in the evening at dinner. Or is it supper? Technically, dinner is actually our lunch time meal and the term supper refers to the evening meal.5 Regardless, in recent years evidence has been published that we are doing this all wrong.
A review of the eating habits of Seventh Day Adventists published in 2017 provides some measure of this.6 Seventh Day Adventists are a Protestant Christian denomination known for the observance of Saturday as the Sabbath. They are also famously vegetarian. The denomination grew out of the Millerite Movement that began with the Reverend William Miller’s prediction that Christ would return on October 22, 1844.
The Church’s followers possess many strong beliefs, including some related to dietary practices. The Church advocates vegetarianism and adherence to Kosher laws. Members abstain from alcohol, tobacco, and some avoid coffee and other caffeinated beverages. John Harvey Kellogg was a member and breakfast cereals have long been associated with the Church. Ellen G White, an early Church leader, advocated for large breakfasts, small dinners, and no snacks between meals.6 This heritage and continued adherence to White’s ideas has made the members of the Church an ideal pool of people from whom to gather data in order to investigate meal timing.
In the 2017 Adventist Health Study-2, Hana Kahleova et al examined meal frequency and timing and their relation to changes in body mass index (BMI).7 They analyzed data from 50,660 adult members of the Church who were more than 30 years old. The number of meals eaten per day, length of overnight fast, consumption of breakfast, and timing of the largest meal of the day were among the variables considered. The primary outcome was change in BMI per year. Eating only 1 to 2 meals per day was associated with a general reduction in BMI each year compared to eating 3 meals per day.7 That doesn’t come as a surprise. Compared to people who ate their largest meal at dinner, those who ate breakfast as the largest meal were more likely to have a reduction in their BMI over the study’s median follow-up period (7.2 years).7
People who eat breakfast have an easier time keeping their weight down compared to those who skip breakfast. Kahleova’s study also found that about 8% of the people finished lunch, technically dinner, in the early afternoon and did not eat again until breakfast, fasting for a period of 18 to 19 hours daily. These people had the lowest BMIs of all.7
The conclusions of this study need to be viewed with caution as the study was observational; the data were collected from members of a religious group that follow multiple practices that are atypical of the general population, but they remain intriguing.
It now appears that our internal circadian clocks modulate energy balance and metabolism and that calories are used more efficiently in the morning than in the evening. Everything being equal as far as calorie intake and exercise go, people will lose more weight if the larger meal is eaten in the morning. Of course, the idea that this is “good” reflects our cultural attitude that weight loss is good and always desirable. One might argue that under famine conditions, the largest meal should be supper.
We do not understand why these variations in calorie burning occur. Are the changes simply metabolic or are there behavioral changes underlying them that we aren’t aware of? A new study now underway, aptly named The Big Breakfast Study, will attempt to answer some of these gaps in our knowledge.8
The twin concepts that breakfast and occasional fasting can both be part of healthier lifestyles are quickly becoming concepts endorsed by mainstream medicine. In January 2017, the American Heart Association (AHA), in their journal Circulation, reviewed research on skipping breakfast and intermittent fasting as it affects obesity, insulin resistance, and cardiovascular disease risk, and issued a policy statement that encourages eating regular meals, including breakfast, and avoiding snacking between meals.9 According to their scientific statement, “Planning when to eat meals and snacks and not skipping breakfast, are patterns associated with healthier diets, which could reduce cardiovascular disease risk.”10
In recent years, the average American diet has trended towards an eating pattern that is the opposite of what the AHA recommends. More people skip breakfast, and a higher percentage of total daily calorie intake comes from snacks consumed between meals rather than from meals themselves. In the last 40 years, women have reduced their meal-derived calories from 85% to 77% while increasing energy from snacks from 18% to 23%. The tendency to eat 3 standard meals per day has also declined in both men and women. Today 20% to 30% of the population regularly skip breakfast.11 People in the United States now eat nearly around the clock rather than sticking to specific meal times. The very idea that meals should be consumed at specific times has been abandoned for a snack food, eat when hungry philosophy that may have been promoted by commercial motives and advertising.10
This current study by Sutton et al that shows eating a full breakfast and extending night time fasting is useful in improving symptoms of prediabetes is important. It adds to this growing body of knowledge behind the AHA’s recommendation. It confirms some of the ideas that Ellen G White was preaching 150 years ago. We are reminded once again that some of the most basic lifestyle habits are of fundamental importance to promoting good health. Not only has the public forgotten these important aspects of health maintenance, so have we as practitioners.
From the writings of Ellen G White:
It is the custom and order of society to take a slight breakfast. But this is not the best way to treat the stomach. At breakfast time the stomach is in a better condition to take care of more food than at the second or third meal of the day. The habit of eating a sparing breakfast and a large dinner is wrong. Make your breakfast correspond more nearly to the heartiest meal of the day.11 Regarding late suppers, she wrote, “For persons of sedentary habits, late suppers are particularly harmful. With them the disturbance created is often the beginning of disease that ends in death.”12
