by Yifan Xia
How would you feel if you were told to not have dinner for the rest of your life? Skipping dinner every day might sound shocking to most of us, but it was once a very common practice in ancient China in the Han Dynasty. In fact, even today Buddhism and Traditional Chinese Medicine (TCM) promote this practice as a healthier choice than eating three meals per day. But does this practice have roots in science? Of course, controversy exists around this topic, but one thing that we can be certain of today is that the timing of our meals can have a much greater impact on our health than we originally thought.
Researchers investigating the circadian system (internal biological clock) have started looking at the effects of mealtime on our health. Surprisingly, preliminary evidence seems to support the claims of Buddhism and TCM, indicating that eating meals earlier in the day might help promote weight loss and reduce the risk of chronic disease.
What are circadian rhythms and the circadian system?
Circadian rhythms are changes in the body that follow a roughly 24-hour cycle in response to external cues such as light and darkness. Our circadian system, or internal biological clock, drives circadian rhythms and prepares us to function according to a 24-hour daily cycle, both physically and mentally.
Why do they matter to our health?
Our internal biological clock is involved in almost every aspect of our daily lives: it influences our sleep-and-wake cycle, determines when we feel most energetic or calm, and when we want to eat.
These days people don’t always rely on their biological clocks to tell them when to eat, and there are many distractions in the environment that can influence mealtime. We typically think how many calories we eat—and what we eat—are the major contributors to our weight and health, but researchers have found that eating at inappropriate times can disrupt the internal biological clock, harm metabolism, and increase the risk of obesity and chronic disease.
What does the research say?
Although currently the body of research evidence for this area is relatively small, there are several human studies worth highlighting. One randomized, open-label, parallel-arm study, conducted by Jakubowicz, D., et al and published in 2013, compared effects of two isocaloric weight loss diets on 93 obese/overweight women with metabolic syndrome. After 12 weeks, the group with higher caloric intake during breakfast showed greater weight loss and waist circumference reduction, as well as significantly greater decrease in fasting glucose and insulin level, than the group with higher caloric intake during dinner. Another study published in the same year with 420 participants noted that a 20-week weight-loss treatment was significantly more effective for early lunch eaters than late lunch eaters. In 2015, a randomized, cross-over trial, conducted in 32 women and published in International Journal of Obesity, showed that late eating pattern resulted in a significant decrease in pre-meal resting-energy expenditure, lower pre-meal utilization of carbohydrates, and decreased glucose tolerance, confirming the differential effects of meal timing on metabolic health. However, few studies were identified reporting negative findings, probably due to the fact that this is an emerging field and more research is needed to establish a solid relationship.
So when should we eat? Is there a perfect mealtime schedule for everyone?
“There are so many factors that influence which meal schedules may be suitable for an individual (including biological and environmental) that I cannot give a universal recommendation,” says Gregory Potter, a PhD candidate in the Leeds Institute for Genetics, Health and Therapeutics (LIGHT) laboratory at the University of Leeds in the United Kingdom and lead author on the lab’s recent paper reviewing evidence of nutrition and the circadian systems, published in The British Journal of Nutrition in 2016. Potter also comments that regular mealtime seems to be more important than sticking to the same schedule as everyone else: “There is evidence that consistent meal patterns are likely to be superior to variable ones and, with everything else kept constant, it does appear that consuming a higher proportion of daily energy intake earlier in the waking day may lead to a lower energy balance and therefore body mass.”
Aleix Ribas-Latre, a PhD candidate at the Center for Metabolic and Degenerative Diseases at the University of Texas Health Science Center and lead author on another review paper investigating the interdependence of nutrient metabolism and the circadian systems, published in Molecular Metabolism in 2016, also agrees: “To find the appropriate meal time has to be something totally personalized, although [it] should not present [too] much difference.” Aleix especially noted that people who are born with a tendency to rise late, eat late, and go to bed late (“night owls” versus “early birds”) are more likely to be at risk for metabolic disease.
Do we have to eat three meals a day?
How many meals do you usually have? In fact, how much food makes a meal and how much is a snack? There is no universal definition, which makes these difficult questions to answer.
“To maintain a healthy attitude towards food, I think it is important to avoid being too rigid with eating habits … I do think consistency is important as more variable eating patterns may have adverse effects on metabolism,” says Potter. “Although there is evidence that time-of-day-restricted feeding (where food availability is restricted to but a few hours each day) has many beneficial effects on health in other animals such as mice, it is as yet unclear if this is true in humans. I’d also add that periodic fasting (going for one 24 hour period each week without energy containing foods and drinks) can confer health benefits for many individuals,” Potter comments.
[See Hannah Meier’s recent article on intermittent fasting for more.]
Based on their research, Ribais-Latre and his lab have a different opinion. “We should eat something every 3-4 hours (without counting 8 hours at night). Many people complain about that but then consume a huge percentage of calories during lunch or even worse at night, because they are very hungry. Eating a healthy snack prevents us [from] eating too [many] calories at once.” He suggests what he considers a healthier mealtime schedule:
– 6:00 am Breakfast (30% total calories)
– 9:30 am Healthy snack (10%)
– 1:00 pm Lunch (35%)
– 4:30 pm Healthy snack (10%)
– 8:00 pm Dinner (15%)
What if you are a shift worker or your work requires you to travel across time zones a lot? Ribais-Latre’s advice is “not to impair more their lifestyle… at least it would be great if they are able to do exercise, eat healthy, sleep a good amount of hours.”
What does Traditional Chinese Medicine say?
There are historical reasons behind the no-dinner practice in ancient China in the Han Dynasty. First, food was not always available. Second, electricity hadn’t been invented, so people usually rested after sunset and they didn’t need much energy at what we now consider “dinner time.”
However, there are also health reasons behind this practice. In TCM theory, our internal clock has an intimate relationship with our organs. Each organ has its “time” for optimal performance, and we can reap many health benefits by following this clock. For example, TCM considers 1:00 am – 3:00 am the time of “Liver”. The theory says that is when the body should be in deep sleep so that the liver can help to rid toxins from our body and make fresh blood. Disruption at this time, such as staying up until 2:00 am, might affect the liver’s ability to dispel toxins, leading to many health problems, according to the theory.
Many Western researchers do not seem to be familiar with the TCM theory. When asked about the practice of skipping dinner, Potter comments, “I think that skipping dinner can be a perfectly healthy practice in some circumstances; in others, however, it may be ill advised if, for example, the individual subsequently has difficulty achieving consolidated sleep.”
On the flip side, Ribais-Latre says that “skipping a meal is not good at all. We should not eat more calories than those we need to [live], and in addition, the quality of these calories should be high… If you can split those calories [to] 5 times a day instead of three, I think this is healthier.”
Even though there is no universal agreement on mealtime, the tradition of “skipping dinner” did come back into style several years ago in China as a healthier way of losing weight, and was quite popular among Chinese college women. Yan, a sophomore from Shanghai and a friend of mine, said that she tried the method for six months but is now back to the three-meal pattern. “The first couple of days were tough, but after that, it was much easier and I felt my body was cleaner and lighter… I did lose weight, but that’s not the main goal anymore… I got up early every day feeling energetic. Maybe it’s because I only ate some fruits in the afternoon, I usually felt sleepy early and went to bed early, which made it easier to get up early the next day with enough sleep… I’m eating three meals now, but only small portions at dinner, and I think I will continue this practice for my health.”
So what’s the take-away?
Mealtime does seem to matter. But exactly how, why, and what we can do to improve our health remains a mystery. Researchers are now looking into the concept of “chrono-nutritional therapy,” or using mealtime planning to help people with obesity or other chronic diseases. When we resolve this mystery, the question of “When do you eat?” will not just be small talk, but perhaps a key to better health.
Yifan Xia is a second-year student studying Nutrition Communication and Behavior Change. She loves reading, traveling, street dancing, trying out new restaurants with friends in Boston, and watching Japanese animations.