Eating Late Can Make You Gain Weight- Food Timing & Weight Loss.

The formula for weight loss has always been a simple concept- if you eat more calories than your body burns you will gain weight- and if you take in less calories than your body uses you will lose weight. It’s a rather rudimentary theory that places emphasis on total calorie intake and energy expenditure and in keeping with this idea the time of day you that eat should have no bearing on whether you will lose weight or gain weight. Eating earlier in the day, eating later in the day, spacing your meals out or getting most of your calories from one big meal in the evening, afternoon or morning- none of these factors should matter given the rather straightforward laws of thermodynamics applied to human energy intake, since all that counts is your activity level and the amount of calories you consume. This approach has been the de facto weight loss method for most clinical weight management programs for decades, but as clear cut as it may seem- it isn’t exactly how our body works as human metabolism is far more complex than this simple algorithm would suggest. In fact, emerging studies continue to reveal that the timing of our meals has far more of an impact on whether we lose or gain weight than was previously thought.[1,2]  These findings, coupled with recent advances in our understanding of molecular biology show that just about every organ and every process in our body is synchronized with the time of day- our metabolism included.[3- something] So much so that eating later in the day- a practice somewhat out of sync with our evolutionary habit of eating during the day time and sleeping at night- can lead to increased incidence of weight gain and reduced weight loss even if total calories are equal to or less than your body’s daily requirements.[1] It’s a finding that challenges (and in some ways invalidates) the simplicity of the ‘calories in versus calories’ out approach to losing weight. In this article we will explore some of the systems in our body that influence how and when we mobilize fat stores based on the time of day and take look at the evolutionary premise as to why eating later at night seems to lead to metabolic discord. It’s a complex subject, but by taking the time to get a handle on how our body deals with food at different times, we can make better decisions regarding our eating habits if body fat reduction is our goal or if we are just trying to eat in as healthy a manner as possible. As always thank you for reading and do be sure to share this article with anyone who you think it will benefit.

Food Timing & Weight Loss In Our New Environment

We are all intimately tied to the planet’s rotation although modern living creates the illusion that we are not.

We are, like every organism on the planet, living products of our natural environment. Beings intimately tied to the diurnal rhythms of the Earth’s rotation. In the over 1 billion years that the gene pool from which modern humans derive our individual genotypes was formed, the biochemistry of every creature on Earth has been selected in some form in accordance to the rising and setting of the Sun.[4,5,6] From an evolutionary standpoint, everything from our behavior to our physiology and our biochemistry are reflections and adaptations to the daily cycle of our planet’s movement around the sun. Yet, most of us living in developed countries inhabit a world very much removed from our evolutionary heritage – one very much out of sync with the rhythms of the planet that spawned us.  Improvements in housing, and our ability to use electricity to extend the average day long past what it was for millions of years has been unquestionably one of the greatest advances of the Industrial Age. No longer huddled over a flame for light after sunset, Thomas Edison’s inventions revolutionized our world in that we are no longer tethered to the rotation of our planet for our cues on when to sleep or to be active. Free of these constraints, we are awake later, we eat later and we sleep later (and less) than ever before in human history.[7] Today, staying up late and sleeping less is not only a norm, but an ideal held by many in our society as a virtue since most equate increased wake time with increased productivity

In terms of productivity our artificial extension of day has been an invaluable boon to our ability to work longer and spend more time doing what we want to do without being obliged to turn in a little after sunset. However, like all of our technological advancements, there is a price, and perhaps a hefty one. Our world has changed drastically over the past several decades but our bodies are very much the same organisms adapted to move during the day and sleep during the night. Changes to these long established patterns wreak havoc on our health as studies show that cardiovascular disease, diabetes, gastrointestinal disorders, depression and other ailments are far more common among those who do not have regular sleeping habits.[8,9,10] Given these findings it makes sense that new research also shows that irregular timing of our meals may have a significant impact in weight regulation.[1]

Food Timing & Weight Loss- Understanding Our Internal Clocks

Our bodies all have inner clocks that regulate our systems based on the time of day. Eating late at night can disrupt natural rhythms and lead to obesity and increased risk of metabolic disease.

All organisms on Earth, be it plant, insect or mammal have built in circadian ‘clocks’ that operate in anticipation of changes in the environment brought on by the rising and setting of the sun.11 Initially it was thought that time of day regulation was the role of the suprachiasmatic nucleus (SCN) [12]- an area of the brain populated by a large number of ‘mini clocks’ called circadian oscillator cells [13,14] which act as a centralized timekeeper and is responsible for dictating our body’s 24 hour based rhythms. However, over the years scientists have discovered that circadian oscillator cells also exist in other regions of the brain and in most, if not all peripheral organs and tissues including the liver, kidneys, pancreas, gut, muscle tissue and interestingly enough- fat tissue. [1,3,15,16,17,18] Now the SCN plays a special role within this system of oscillator cells by determining the time of day using information regarding the levels of light coming from special cells in your retina. Environmental cues that tell our bodies what time of day it is are called zietgebers and it makes sense that light levels would be our bodies’ principal form of orientation. That being said, new findings show that circadian oscillator cells in other parts of the body rely on other zietgebers to determine time with meal timing and food availability being one of them. [19,20,21]

The problem is that the SCN relies on light cues, whereas peripheral circadian oscillator cells use stimuli such as food timing to determine the body’s perception of the time of day.[2,12] Consequently, by eating later into the night your brain is getting a signal from one zeitgeber (light) saying it’s dark outside and thus time to sleep (and burn fat) whereas another zietgebers in the form of food is saying it’s time to be active and store fat. Those conflicting signals appear to deregulate metabolism and may be one of the reasons why shift workers and individuals with later schedules have such higher rates of metabolic related disease and obesity.

Meal Timing For Weight Loss- How Eating At The Wrong Time Makes You Gain Weight

Eating late at night can make you gain weight independent of calories consumed for the day.

Adipose tissue also have circadian oscillator cells with their own time sensitive rhythm of accumulation and mobilization called temporal compartmentalization. While asleep, our body burns fat and while awake our body stores fat, thanks in part to oscillators in the liver that control the use of glucose or fats as an energy source. [22,23,24] Genes responsible for using sugars as the body’s primary fuel source (PFKFB3, FUK, MPI and PFKM) have high expression levels in the morning and drop in the afternoon through the evening.[22] On the other hand what are referred to as ‘fuel accumulation’ genes (HMGCR, HMGSC1), that store fat have low levels in the morning and increase as the day goes on.[22]

In fact, the time you eat appears to affect whether you will lose weight or gain weight, even if you are ingesting less calories than your body needs to remain in energy balance. A groundbreaking Spanish study set out determine whether the timing of food intake would influence the success of a weight loss diet. It was a comprehensive endeavor as researchers were also able to look at any genetic, physiological and behavioral factors that may have affected the results. For the study, 420 overweight men and women following a clinically supervised weight loss diet were tracked for 20 weeks and the results were eye opening to say the least. Those who ate their meals later in the day lost significantly LESS weight than those who ate their main meals earlier in the day, even though they all ate more or less the same amount of calories, ate the same proportions of protein, fats and carbohydrates and had the same energy expenditures. [1]  This was the first human study to observe this occurrence but studies with animals have had similar finding. Several studies with mice, who are nocturnal and have a time system that is the reverse of ours as they eat and are active mainly at night and sleep during the day, show that when two groups of mice with identical activity levels are fed exactly the same amount of calories but at different times there are significant differences in weight gain. Those fed on a schedule during the day when they would ordinarily be asleep gained weight and increased their body fat, while those fed at night in keeping with their normal biorhythms did not. [2,25,26,27] Thus indicating that the time that food is consumed is an important factor responsible for weight gain independent of calorie intake.[1]

How Eating At Night Affects Our Bodies
Observations of the higher incidence of obesity among shift workers when compared to day workers with the same energy intakes and activity levels[41] for years have been the smoking gun indicating that this phenomenon does indeed occur in humans, along with studies that show increased obesity among non-breakfast eaters when compared to those who do eat breakfast and among and those diagnosed with night eating syndrome. [28,29] (See my Ebook on Eating Breakfast & Weight Loss) It was initially thought that weight gain associated with night time eating was due to a tendency to gravitate to high calorie processed foods, which are exceptionally easy to overeat and thus raising the likelihood of eating more than you should and consequently gaining weight.[30,31,32] (Read my earlier article on Night Eating Syndrome) However, we know now that overeating may not necessarily be the culprit as these studies show that weight gain can occur independent of energy intake when meals are predominantly eaten later in the day.


As of now we don’t exactly understand the all of the mechanisms that link weight loss and weight gain to meal timing. It was thought that changes in levels of hormones responsible for making you feel full or satisfied after a meal such as leptin or ghrelin may have been responsible.[33,34] Possibly as a result of a decoupling from the body’s light based inner clock, but in the Spanish study, blood tests showed no differences in satiety-related hormone levels between the early eaters and the late eaters. Lack of sleep has also come into question as a causative factor with regards to weight gain as several studies show associations between short sleep duration and risk of obesity and impaired weight loss.[35,36,37] (See my article on Lack of Sleep and Weight Gain). However, in the Spanish study even though the late eaters went to bed later than early eaters there were no real differences in sleep duration or reported quality between the two groups. [1] Other animal and human studies have also failed to find associations with decreased sleep and weight gain[2,38] but what researchers did find were differences in a very time sensitive gene called CLOCK.

CLOCK stands for Circadian Locomotor Output Cycles Kaput (who ever said scientists don’t have a sense of humor) and it’s one of the genes found in mammals that are responsible for the persistence and duration of our body’s daily rhythms along with another transcription factor called BMAL1. You can think of these genes as the driving forces behind the circadian oscillator cells found in the SCN and peripheral organ tissues that we mentioned earlier. In the Spanish study, there was a higher occurrence of a variation in the CLOCK gene (called rs4580704) among those who ate later in the day- a variation that seems to manifest as a result of irregular food timing. Interestingly enough, other studies have associated this particular genetic mutation with increased susceptibility to obesity and metabolic disease.[39,40] Other variations (called polymorphisms) in the CLOCK gene have also been linked with increased insomnia, difficulty losing weight and increased depressive episodes among those with bipolar disorders.[41,42,43] however this study was the first to report an association between CLOCK gene variations and the timing of food intake.

Meal Timing: Practical Tips For Weight Loss And Preventing Weight Gain
The most significant observation from this study was that those who had lunch as their largest meal of the day (in the Mediterranean breakfast is usually small and lunch is the main meal) were the ones with the greatest amount of weight loss.[1] Eating a large lunch- which represented for the participants in this study, as much as 40% of their daily energy intake appears to reset the mini clocks in our organs either indirectly or through changes in timing relative to other meals during the day.[1] Weight loss differences in this study did not hinge on what time dinner or breakfast was eaten- just lunch, however that doesn’t necessarily mean that eating an early lunch is the only way to optimize weight loss. Researchers observed that the late lunch eaters also had a far higher tendency to have skipped breakfast or to have had a smaller than usual breakfast. Such a long time lapse between the first meal of the day and lunch seems to create a prolonged semi-fasted state and lowers blood sugar levels- which can have a negative effect on glucose metabolism and could have contributed to the difference in weight loss. Thus underlining the wisdom of having regular meals starting with a good breakfast to maintain adequate glucose metabolism. For while the study did not look at a population where eating a large breakfast is a common practice, the fact that most of the late eaters did not eat breakfast and the many studies that do verify a link between the consumption of a high protein, high carbohydrate breakfast with increased success in weight loss and lower incidence of obesity[44] leaves little room for doubt that eating breakfast is an important part of the equation.

So what weight loss and weight gain preventative recommendations can we glean from these new studies and advances in molecular biology? There are several:

• Eat the majority of your calories earlier in the day.
• Don’t skip breakfast.
• Eat meals at regularly spaced intervals the same time everyday instead of erratically.
• Avoid high calorie meals later in the day.
• Try to keep a schedule that makes it less likely that you will be eating later in the day.

In spite of our desire to extend our days there is in fact a genetically hardwired ‘wrong time’ to eat as we are unquestionably maladapted to eating at night. Taking this into consideration anyone attempting to lose weight or prevent weight gain and or achieve optimal health would do well to ensure that they ate most of their calories earlier in the day. My own experience with my clients undergoing extreme weight loss (50lbs-110lbs) is observational at best but they all consumed most of their calories earlier in the day following my recommendation to ‘breakfast like a king, lunch like a prince and dine like a pauper’ with an additional directive to turn in early and not to eat too into the night. I hope this article helped highlight the importance of meal timing with regards to weight loss and maintaining a healthy body weight and while some of the lessons may not be convenient for many of us- they are important nonetheless as we are very much still creatures intimately tied to the rotation of the Earth. Thanks as always for reading.