Should You Avoid Eating at Night?
I hate to be the bearer of bad news, but maybe there are good reasons to avoid eating at night. (I’m not talking about the old myth that says that anything you eat past 6 p.m. just magically turns into fat). I know that this is going to directly contradict and probably upset a lot of current popular diets and diet experts…and I’m okay with that. I don’t write to make friends; I just enjoy reading about training and passing some useful information on.
The first group of people who will probably cry about this are the science guys who disregard everything that suggests that there might be more to dieting than the energy balance of calories-in vs. calories-out. Shortly after the calorie guys, however, come the “it’s all about the macros, bro” guys. If only the human body was as simple as those in the fitness industry makes it seem. I am not debating the importance of your caloric balance and your macronutrient/micronutrient intake, but there’s some really interesting research regarding our body’s circadian rhythm, which may make nutrient timing even more important.
This brings me back to my days as an overly tired student trying to escape my neuroscience classes. Our master clock, or biological clock, is a small part of the brain referred to as the suprachiasmic nucleus (SCN). This clock helps to keep your body on schedule so to speak. The body follows “circadian rhythms”, primarily in response to light/darkness and these rhythms have an effect on almost all physiological processes.
Basically, your body has a schedule that it likes to follow everyday. Based off this 24 hour schedule, you will release certain hormones during specific time periods. An example is releasing testosterone and cortisol in the morning to promote alertness or secreting melatonin at night to promote sleep. It does this by following cues from our external environment, like the time of day.
There are also peripheral clocks throughout the body which keep tabs on energy status. So, in order to make sure these “systems” are operating properly, our bodies should have periods of low food intake—and this should be in sync with our nighttime or inactive phase. Feeding during the inactive phase is associated with a host of undesirable things like increased body fat, glucose intolerance, and inflammatory disease.
The first study I want to share was a study done on mice called, “Time-Restricted feeding without reducing caloric intake prevents metabolic diseases in mice fed high fat diet.” In this study, the researchers were trying to determine if obesity results from a high fat diet or from a disruption of metabolic cycles, namely circadian rhythms.
There were two groups of mice. One group had a feeding window that was time restricted to eight hours (tRF) and the other ate ad libitum (whenever they wanted). (Calories were the same and from a high fat diet in both groups). The time-restricted mice were protected against obesity, hyperinsulinemia, inflammation, and had improved motor coordination, glucose tolerance . They also experienced improved oscillations of the circadian clock, improved nutrient utilization, and improved energy expenditure . Here’s a picture from the study.
If you are wondering why the cheese on the right is over the moon it’s because mice have an opposite circadian rhythm for activity than humans do, so nighttime is actually their “active phase”. It makes sense that we do not want to eat much during our inactive phase. If we consistently eat during our inactive phase (at night), it will cause our peripheral clocks to be out of sync with the master clock in our brain.
Another interesting study shows that not only when we eat matters, but that the macronutrient consumption during specific times matters as well. The study, “Time-of-Day-Dependent Dietary Fat Consumption Influences Multiple Cardiometabolic Syndrome Parameters in Mice,” made some very intriguing points.
Here were some of the most interesting quotes from the study:
- “Mice fed a high fat meal at the beginning of the active period retain metabolic flexibility in response to dietary challenges later in the active period.”
- “Conversely, consumption of high fat meal at the end of the active phase leads to increased weight gain, adiposity, glucose intolerance, hyperinsulinemia, hypertriglyceridemia, and hyperleptinemia (i.e., cardiometabolic syndrome). The latter perturbations in energy/metabolic homeostasis are independent of daily total or fat-derived calories.”
- “We report that high fat feeding at the transition from sleeping to waking appears to be critically important in enabling metabolic flexibility and adaptation to high carbohydrate meals presented at later time points. Conversely, high carbohydrate feeding at the beginning of the waking period dramatically impairs the metabolic plasticity required for responding appropriately to high fat meals presented at the end of the waking period.”
- “… A high carbohydrate morning meal appears to “fix” metabolism toward carbohydrate utilization and impair the ability to adjust metabolism toward fat utilization later in the waking period.”
These points all make sense. A high fat breakfast seems to set the body towards higher fat oxidation, whereas high carbohydrates in the morning set the stage for carb oxidation as opposed to fat oxidation. We want to maintain metabolic flexibility so that we can use our body’s stored fat as fuel during the appropriate times. There are a plethora of benefits to having periods where insulin is low, as I have mentioned in earlier article’s and a carbless breakfast or no breakfast helps keep insulin levels below. I wrote on an anabolic breakfast (Read Here) which also presented some research as to why it may be beneficial to avoid carbohydrates at breakfast.
So, should you avoid all food at night? No, that would be awful but maybe you should limit some things. Despite what you have heard about nighttime carbohydrate consumption, it is not bad. However, fat intake at night does seem to have some negative consequences. In the study “Greater Weight Loss and Hormonal Changes After 6 month Diet with Carbohydrates Eaten Mostly at Dinner,” Israeli Police officers were split between having the majority of their carbohydrates in the morning vs. at night. It’s not the most intelligently laid out study, but the results clearly show that the nighttime carb eaters dropped more percent body fat, were more satiated, increased insulin sensitivity, had higher leptin, and improved blood glucose levels.  Those that preach carbohydrates at breakfast counter with, “but insulin sensitivity is highest in the morning.” This is true, but it’s for muscle and fat cells. So it’s kind of a moot point.
Understanding the importance of our circadian clock goes beyond physique enhancement. A study presented in the Endocrine Review, “Metabolism and Circadian Rhythm-Implications for Obesity,” offers a very in-depth look at the intricacy of our circadian clock and the various roles it plays in our body. In their conclusion they state, “Western lifestyle leads to high food consumption, inactivity during the active period, enhanced activity in the rest period, and shortened sleep period. This lifestyle may cause high parasympathetic output to the viscera leading to obesity, hyperinsulinemia, and hyperlipidemia, or high sympathetic output to the muscle and heart leading to vasoconstriction and hypertension. Indeed, disrupted biological rhythms might lead to attenuated circadian feeding rhythms, disrupted metabolism, cancer proneness, and reduced life expectancy.” 
There is too much research to not accept that food timing absolutely does matter. Why? Because our circadian rhythm regulates energy homeostasis, and our type and timing of food has a direct effect on our circadian rhythm.
So, here are some tips on how to use this information in your diet:
- Carbohydrates are not necessary at breakfast. Instead, opt for a protein/fat breakfast or fast during this time. If fasting, make sure that you are consuming water as dehydration will take away from some of the beneficial fasting effects.
- Watch your fat intake and calorie intake at night or during your “inactive” phase.
- You do not need to eat all day long, and you definitely don’t need to eat every two to three hours. Let your body shift between its natural anabolic and catabolic processes which leads to improved health in the long term.
- Intermittent Fasting can be used to improve circadian rhythms, decrease body fat and has plenty of longevity and anti-aging effects that I discuss this in my book
- If you are more concerned with the health aspect of fitness and maximized fat loss, then look into fasting and restricted feeding windows.
 Time-Restricted Feeding without Reducing Caloric Intake Prevents Metabolic Diseasesin Mice Fed a High-Fat Diet. http://ac.els-cdn.com/S1550413112001891/1-s2.0-S1550413112001891-main.pdf?_tid=c750109e-f49c-11e2-ae2a 00000aab0f27&acdnat=1374696677_72ab1ee995d0238c698cdcd2cbc37d26
 Time-of-Day-Dependent Dietary Fat Consumption Influences Multiple Cardiometabolic Syndrome Parameters in Mice. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3021134/
 Greater Weight Loss and Hormonal Changes After 6 Month Diet with Carbohydrates Eaten Mostly At Dinner. http://www.sciencedaily.com/releases/2012/11/121111153640.htm
 Metabolism and Circadian Rhythms—Implications for Obesity. http://edrv.endojournals.org/content/31/1/1.long