One of the common statements heard today, is not to consume carbohydrates at night, when it comes to weight loss. Some dieticians or coaches, even mention the timings, like 7pm or 8pm etc.
In fact, while speaking to people, this is the most common statement I get to hear. When I ask them, a simple “why”, the answer they give is almost often, “everyone says it”.
The reason they give me is that because the metabolism slows down at night, so if we eat carbs, it will not be digested get converted to fat. Convenient, but it’s not that simple. Correlation does not mean causation. If something is correlated to something else, it does not mean, it is the cause of that thing.
When I did my research to uncover the truth, the studies were quite contradicting. But the conclusion was clear.
To support the fact, that eating at night does not lead to weight gain, here are the studies:
- A 2007 study, determined the influence of meal time on salivary circadian cortisol rhythms and weight loss in obese women. Twelve obese women (body mass index >40 kg/m(2)). During the study, in stage 1, the subjects received a hypocaloric diet (1000 kcal/d) portioned into five meals per day. In stage 2, the subjects received the same diet between 0900 and 1100 h. In stage 3, they received the same diet between 1800 and 2000 h.
Study found that, the administration of a hypocaloric diet led to changes in weight, body composition, resting metabolic rate, and nitrogen balance but did not significantly alter salivary circadian cortisol rhythms. Changes in weight, body fat, and fat-free mass did not significantly differ across the three periods.
2. A 2011 study, investigated the effect of a low-calorie diet with carbohydrates eaten mostly at dinner, in Seventy-eight police officers (BMI >30), for 6 months. This was in comparison to an identical low-calorie diet providing carbohydrates throughout the day.
Research found that, greater weight loss, abdominal circumference, and body fat mass reductions were observed in the carb at night diet in comparison to controls. Hunger scores were lower and greater improvements in fasting glucose, average daily insulin concentrations, T-cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, C-reactive protein (CRP) etc. levels were observed in comparison to controls.
The study demonstrated improvement in hunger/satiety status, persistence in the weight loss process, better anthropometric outcomes, improved insulin sensitivity, improvement in metabolic syndrome parameters, less inflammation and hormonal changes, following ‘carbs at night’ diet, as compared to eating carbs the entire day.
3. In a 2015 study, researchers with carbohydrates concentrated at dinner, demonstrated improved satiety along with better anthropometric, metabolic, and inflammatory status.
4. A 1997 study, determined whether meal ingestion pattern [large morning meals (AM) vs. large evening meals (PM)] affects changes in body weight, body composition or energy utilization during weight loss. This 105-day, study involved 10 overweight and obese adult women in a metabolic ward.
The authors found that during the first phase (first 6 weeks), participants who ate most of their daily food at night (p.m. eaters) lost more fat and less lean mass than those who ate most of their food in the morning (a.m. eaters). However, during the second cross-over phase (when participants switched groups), a.m. eaters lost more fat than p.m. eaters.
Researchers concluded that, ingestion of larger AM meals resulted in slightly greater weight loss, but ingestion of larger PM meals resulted in better maintenance of fat-free mass. Thus, incorporation of larger PM meals in a weight loss regimen may be important in minimizing the loss of fat-free mass.
Then there were studies, which supported the theory of weight gain due to eating late at night:
- A 2013 study, tested whether a change in meal timing, switching between a high-calorie breakfast and a high-calorie dinner, with an overall similar daily caloric intake has a different impact on weight loss, appetite scores, and other characteristics of the metabolic syndrome.
For the study 93 Overweight and obese women with metabolic syndrome were divided into two groups, each consuming 1400cal/day for weight loss. They were divided into two parts, a breakfast (BF) (700 kcal breakfast, 500 kcal lunch, 200 kcal dinner) or a dinner (D) group (200 kcal breakfast, 500 kcal lunch, 700 kcal dinner) for 12 weeks.
Researchers found that, the breakfast group showed greater weight loss and waist circumference reduction, better insulin sensitivity and hunger suppression.
2. A 2013 study, examined the short-term effect of night eating restriction (NER) on daily EI in healthy young men. For the study, 29 men initiated a 2-week NER intervention (elimination of EI from 1900 to 0600 hours) and a 2-week control condition.
Study found that, during the NER condition, the participants consumed less total energy/day than during the control condition. Thus, the study provides initial evidence that restricting night-time eating may promote a short-term reduction in total energy intake in a young male population.
3. Acc. to a 2015 study, obesity and late-night food consumption are associated with impaired glucose tolerance. Late-night carbohydrate consumption may be particularly detrimental during late pregnancy because insulin sensitivity declines as pregnancy progresses. Further, women who were obese prior to pregnancy have lower insulin sensitivity than do women of normal weight. Researchers in the study, found whether night-time carbohydrate consumption is associated with poorer glucose tolerance in late pregnancy. For the study, forty non-diabetic pregnant African American women were recruited.
Researchers found that, among only those who were obese in early pregnancy, late-night carbohydrate intake was positively associated with greater glucose concentrations following the oral glucose load, and inversely associated with insulin secretion and the ability of insulin secretion to compensate for reduced insulin sensitivity.
Together, these results suggest that late-night carbohydrate intake may be associated with impaired metabolic health during pregnancy, particularly among women who were obese prior to pregnancy.
4. A 2017 study, examined the relations between the timing of food consumption relative to clock hour and endogenous circadian time, content of food intake, and body composition. For the study, 110 participants, aged 18–22yr, were enrolled for 30 days.
Researchers found that, non-lean individuals (high body fat) consumed most of their calories 1.1h closer to melatonin onset, the beginning of the biological night, than did lean individuals (low body fat). Researchers showed that, the timing of food intake relative to melatonin onset was significantly associated with the percentage of body fat and body mass index.
These results provide evidence that the consumption of food during the circadian evening and/or night, independent of more traditional risk factors such as amount or content of food intake and activity level, plays an important role in body composition.
5. Acc. to a 2020 study, your daily biological clock and sleep regulate how the food you eat is metabolized; thus the choice of burning fats or carbohydrates changes depending on the time of day or night.
Researchers monitored the metabolism of mid-aged and older subjects over two separate 56-hour sessions. In each session, lunch and dinner were presented at the same times (12:30 and 17:45, respectively), but the timing of the third meal differed between the two halves of the study. Thus in one of the 56-hour bouts, the additional daily meal was presented as breakfast (8:00) whereas in the other session, a nutritionally equivalent meal was presented to the same subjects as a late-evening snack (22:00). The duration of the overnight fast was the same for both sessions.
Whereas the two sessions did not differ in the amount or type of food eaten or in the subjects’ activity levels, the daily timing of nutrient availability, coupled with clock/sleep control of metabolism, flipped a switch in the subjects’ fat/carbohydrate preference such that the late-evening snack session resulted in less fat burned when compared to the breakfast session. The timing of meals during the day/night cycle therefore affects the extent to which ingested food is used versus stored.
6. A 2020 study, examined the impact of late dinner on nocturnal metabolism in healthy volunteers. The researchers studied 20 healthy volunteers (10 men and 10 women) to see how they metabolized dinner eaten at 10 p.m. compared to 6 p.m. The volunteers all went to bed at 11 p.m.
The researchers found that blood sugar levels were higher, and the amount of ingested fat burned was lower with the later dinner, even when the same meal was provided at the two different times. On average, the peak glucose level after late dinner was about 18 percent higher, and the amount of fat burned overnight decreased by about 10 percent compared to eating an earlier dinner.
7. A 2018 study, investigated whether dinner immediately before bed, snacks after dinner, or combinations of both were associated with metabolic syndrome and its components in a large Japanese cohort. Researchers enrolled 8153 adults aged 40–54 years who participated in specific medical checkups in an Okayama facility from 2009 to 2010 and from 2013 to 2014. Metabolic syndrome and its components in participants with both night eating habits for an average of 3.9 years were evaluated.
Having both night eating habits, “dinner immediately before bed” and “snacks after dinner”, was associated with higher BMI in both Japanese men and women. Men with both habits showed higher odds of dyslipidemia when compared to those with neither habit. Women with both habits had higher odds of metabolic syndrome and abdominal obesity when compared to those with neither habit. In men and women, both night eating habits were associated with dyslipidemia.
On the third end, are the studies which actually don’t indicate clearly but may need a mention:
- A 2014 study, evaluated the relationship between the timing of meals with caloric intake and BMI while controlling for the timing and duration of sleep. Results demonstrated that the timing of meals was associated with overall energy intake but not with BMI.
Results suggest that later relative timing of meals, particularly eating close to sleep, could lead to weight gain due to a greater number of eating occasions and higher total daily caloric intake.
2. A 2011 study, evaluated the role of sleep timing in dietary patterns and BMI, in over fifty females. Researchers found that, fifty-six percent were “normal sleepers” (<5:30 AM) and 44% were “late sleepers” (≥5:30 AM).
Researchers found that, late sleepers had shorter sleep duration, later sleep onset and sleep offset and meal times. Late sleepers consumed more calories at dinner and after 8:00 PM, had higher fast food, full-calorie soda and lower fruit and vegetable consumption. Higher BMI was associated with shorter sleep duration, later sleep timing, caloric consumption after 8:00 PM, and fast food meals. The findings indicate that caloric intake after 8:00 PM may increase the risk of obesity, independent of sleep timing and duration.
NES (NIGHT EATING SYNDROME)
NES or Night Eating Syndrome is a condition wherein an individual combines sleep disorders with eating disorders. Night eating syndrome (NES) was first described in 1955 as a disorder defined by morning anorexia, evening hyperphagia (consuming 25% of the daily food intake after the evening meal), and insomnia. NES has been attributed to a delay in the circadian rhythm of eating, characterized by appetite suppression during morning hours and appetite increase during evening hours.
The causes of NES are not very clear, and can be due to certain hormones. People who are obese, suffering from an eating disorder, or have had issues of depression, anxiety and substance abuse, are more likely to have NES. But for that, you need to see a good clinical psychiatrist, to ascertain the problem.
A 2012 study, characterizes night-eating syndrome (NES) by increased late-night eating, insomnia, a depressed mood and distress. It is evident that prevalence is higher among weight-related populations than the general community. However, NES does not always lead to weight gain in thus certain individuals may be susceptible to night-eating-related weight gain.
A 2014 study, found that, NES also occurs among non-obese individuals, who appear to be younger than obese individuals with NES. In the study, researchers investigated the relationships between age, body mass index (BMI), and night eating severity in over twenty-three hundred German adults.
It was found that age moderated the relationship between night eating severity and BMI. Specifically, night eating was positively associated with BMI in participants who were between 31 and 60 years old, but not in younger (<31 years) or older (>60 years) participants. Results indicate that age may indeed play an important role when examining the relationship between night eating and obesity. That is, weight gain may only occur after longer periods of engaging in night eating and, thus, no or only small relationships can be found in younger samples such as students.
The purpose to discuss NES, was to understand the studies related to it, wherein it has been shown that despite of having a syndrome like NES, wherein the patient binges large amount of food at night, weight gain doesn’t happen so easily. This is because his morning appetite is generally suppressed, and if he is able to balance the total calories in a day, the weight gain is not a general possibility.
DOES METABOLISM SLOWS DOWN AT NIGHT?
A common statement related to less food intake or less carb intake at night, is due to the fact that, the metabolism decreases at night. Let’s understand the reasoning behind this based on studies.
Acc. to a 2010 study, human sleep comprises of non-rapid eye movement sleep (NREM) and REM sleep. NREM is further comprised of three stages (stages N1, N2, and N3). N3, also referred to as slow wave sleep, is considered deep sleep with the body being least metabolically active during this period. REM sleep is characterized by vivid dreams, loss of muscle tone, and rapid eye movements. NREM and REM sleep occur alternatively in cycles of around 90 minutes throughout the night. The first half of the night is predominantly NREM, and the second half is predominantly REM sleep.
Researchers further suggests that, sleep architecture, though, is heavily influenced by genetic and environmental factors including sex, race, socioeconomic status and culture among others. Sleep duration in mammals generally depends on the size of the animal. Elephants require only 3 hours of sleep while rats and cats can spend up to 18 hours in sleep. It is postulated that this may be due to differences in metabolism. Smaller animals have higher metabolic rate and higher body and brain temperatures compared to larger animals.
When it comes to metabolism during sleep, the study found that, during normal sleep the metabolic rate reduces by around 15% and reaches a minimum in the morning in a standard circadian pattern. However, the basal metabolic rate constitutes 80% of the metabolism needed to maintain all cellular processes in the body.
Let’s understand the basics first:
TEE (total energy expenditure) – is the amount of energy (calories) spent on an average in typical day.
To calculate TEE, the formula is:
TEE = BMR (BASAL METABOLIC RATE) + TEF (THERMIC EFFECT OF FOOD) + ENERGY EXPENDED DURING PHYSICAL ACTIVITY (app. 20% of total TEE)
BMR or Basal Metabolic Rate is the energy required for core body functions and is measured at complete rest without food and it accounts for app. 60% of daily energy expenditure in a sedentary person. This depends on your genes and body composition. More muscles mean, higher BMR. Bigger body size will increase your BMR.
Thermic Effect of Food (TEF), which accounts for around 10% of the daily energy needs. This is basically the effect which one gets from digestion and absorption of food.
Energy expenditure in the name of Activity Thermogenesis which is further divided into 2 types Exercise Activity Thermogenesis (EAT) and Non-Exercise Activity Thermogenesis (NEAT).
A 1988 study, suggested that, the WHO recommendations for energy requirements assume that the energy cost of sleep is equal to the basal metabolic rate (BMR). Goldberg & team, tested over 80 individuals, and found that the use of BMR to estimate overnight energy expenditure would introduce an average overestimate of approximately 5 per cent during the actual hours of sleep, but that when applied over 24 h the error becomes negligible.
This means when we take the above formula the BMR is the same when sleeping. We can call it SMR or Sleeping Metabolic Rate. So the new formula would be:
TEE = SMR (SLEEPING METABOLIC RATE) + TEF (THERMIC EFFECT OF FOOD) + ENERGY EXPENDED DURING PHYSICAL ACTIVITY (app. 20% of total TEE)
Of course, the energy during physical activity would be zero here. So, TEE = SMR (SLEEPING METABOLIC RATE) + TEF (THERMIC EFFECT OF FOOD)
That’s the 15-20% reduction we have during sleep, due to physical inactivity. Rest all the processes continue as it is.
A 2009 study, found that, energy expenditure decreased during the first half of the night, reached a nadir (a 35% decrease), i.e. during the NREM sleep. But energy expenditure during REM sleep increased.
A study, also found that, the lower metabolic rate occurs during non-REM sleep, which provides an opportunity to deal with the damage done during awake and metabolically active period. The metabolism then increases in the REM sleep mode.
Thought the exact reasons for increase or decrease of metabolism during sleep are not clear. It can be due to decrease in physical activity, changes in body temperatures and basic circadian rhythms.
Now, when we take the above logic, we see that, during sleep, the body is spending energy, in digesting the food, you consumed before sleep; i.e. the TEF is still burning calories.
In fact, a 2015 study, suggested that, a bedtime supply of nutrients can promote positive physiological changes in healthy populations. In addition, when night time feeding is combined with exercise training, any adverse effects appear to be eliminated in obese populations. Lastly, in Type I diabetics and those with glycogen storage disease, eating before bed is essential for survival. Nevertheless, night time consumption of small (app. 150 kcals) single nutrients or mixed-meals does not appear to be harmful and may be beneficial for muscle protein synthesis and cardiometabolic health.
So, the metabolism does slow down a bit at night, and its natural; but then it speeds up during the day, and further high as your physical activity increases. Will exercising for 24hrs make sense, just so that your metabolism remains high? Your body naturally needs periods of rest and recuperation along with work. Sleep helps maintain the optimal biochemistry of the body by giving it adequate recovery.
If we conclude the total findings, we see that the scale is somewhere in the middle. So, there is no definite answer, as to which way of eating is best for weight loss. However, due to this, as there are many factors which govern the way we consume our calories. In fact, eating at night is not even a factor to be considered in terms of weight loss.
It’s not about carbohydrates, it’s always about total quantity and quality of food you take in during the day. For someone working out at a high intensity and lifting heavy in the evening hours, need to recover well post workout, and nutrition for them, would be the best thing they probably can have in the entire day. For pro sportsmen, intermittent fasting or skipping meals can be disastrous.
On the other hand, there are people who have night shifts like pilots, flight crew, IT employees, BPO workers, defence forces personnel etc. What about these people? Clearly, the statement of skipping carbs at night or not having dinner, is not an option here.
Then there are children, pregnant women, and other such populations, who should not be skipping meals, and for whom early dinners are not needed.
If you have pastries, pizzas and donuts, during the afternoon hours, thinking that not eating carbs at night will help, then I’m sorry. Your body doesn’t work with time. It works as a whole. Excess calories at any time of the day, will get stored as excess fat (except calories from proteins sources, as they don’t get converted to body fat, that easily).
When we consider our traditional Indian meal, we have been following the 2-3 meals a day formula since centuries. In some places, specially villages and tribal areas, the eating pattern is generally 2 major meals a day, one during the afternoon hours, like a brunch, and then in the evening hours, after sunset. In cities, where the electronic lighting is dominant, the meals are three, with varied timings. This in no way decides how much fat a person would be. It’s about what he eats and in how much quantity he eats.
We need to take into consideration the practicality of lifestyle and an individual case to case basis. Acc. to examine.com “While late-night eating isn’t inherently bad, the impact of meal timing is probably quite different in different people: Some people have a tendency to binge on tasty foods when they’re tired, while others don’t get hungry in the hours before bed. Circadian rhythm factors are another reason why some might want to stay away from eating too much late at night.”