It is the night before an exam. Midnight is quickly approaching and the nerves are starting to settle in. As you reach to grab your calculator you hear your stomach grumble and realize that your mind has wandered – you are wishing that your calculator were actually a late-night snack. How could six hours have already passed since you last ate dinner?! Out of impulse you head downstairs to the kitchen to grab the first goodie that you see when – HOLD IT RIGHT THERE! Take a minute to think twice about grabbing that moonlight meal. By snacking after 8pm you may be inching your way closer towards developing risk factors for obesity, diabetes and cardiovascular disease!
Wait, what is going on here?
Late-night “shift workers” are forced to eat at different (and often rather unnatural) times of day than “day workers.” Multiple cohorts of shift workers have been utilized to study the effects of late-night eating upon health. Various studies have found associations between late-night shift work and the incidence of weight gain and chronic disease (cardiovascular disease, diabetes and obesity). Antunes et al. summarizes that when comparing the diets of day workers to those of night-shift workers, that there is an equivalent amount of total energy in their diets, yet there is a consistent relative increase in weight gain observed amongst the night-shift workers only. Yes, there is a small chance that this weight gain could be fueled by poorer eating habits and food choices made by shift workers, but the influence of shift-work upon weight gain is much more likely to be correlated to metabolic disturbances that result from snacking at times that our bodies are not accustomed to: late at night.
Let’s check out the physiology behind late-night-snacking…
You might be thinking, “It seems like we are making a leap between the two Oreos that I just ate while studying late at night and chronic disease. How exactly are these events connected?” There are two main physiological concepts whose interactions have been revealed as significant contributors to the chronic health risk factors associated with late-night snacking.
The main event: Hormonal and metabolic responses
Glucose is an important metabolic intermediate that provides energy for the body. Dietary glucose is derived from carbohydrates and is often found at high levels in the blood just after a meal. Insulin is an important regulatory hormone that is released from the pancreas in response to elevated blood glucose levels. This hormone acts to influence the uptake of glucose by the liver, skeletal muscles and fat tissue, where it is then stored as glycogen and triacylglycerides (TAG, fat).
Studies have found that levels of blood glucose and TAG are significantly higher after eating a late-night meal (after 1am according to the study) as a result of increased insulin resistance at night. Considering that insulin plays a role in the uptake of both glucose and TAG into cells within the body, it would then follow that increased insulin resistance at night would result in elevated blood glucose and TAG levels since it can not act as readily to influence the uptake of these nutrients into cells. Al-Naimi revealed that after returning to a normal diet schedule, insulin and glucose levels were restored, yet TAG levels remained elevated for two days proceding the late-night meal. This result of prolonged elevation of TAG is of particular concern considering that both insulin resistance and elevated TAG are independent risk factors for cardiovascular disease.
The man behind the curtain: Circadian rhythms
Circadian cycles play an important role in the body’s ability to maintain balance, particularly in relation to physiological and metabolic events. These rhythms are controlled by a a cluster of nerves in the brain, are structured in 24 hour cycles, and mediate physiological responses to light and darkness. Deviations from the inherent cycles established by circadian rhythms are what cause an imbalance in the body’s ability to react metabolically to late-night meals. The inability of circadian rhythms to adapt to abrupt changes in metabolic patterns (as manifested by shift work or late-night snacking) serves as the driving factor for an increased propensity towards developing chronic disease. Studies have shown that the imposition of an abrupt change upon the circadian eating patterns in concert with sleep deprivation act to accelerate the negative effects of glucose intolerance, insulin resistance and dyslipidemia – each of which are independent risk factors for chronic disease.
Even while throwing off your circadian rhythms by eating a snack during that one late-night study session may not occur as frequently as metabolic disruptions imposed by a shift-workers’ routinely changing schedules, the science shows that it is this circadian rhythm disruption that is the problem here. It is likely that you are not increasing your risk of developing chronic disease by indulging in an all-nighter snack once or twice, but if you have developed a habit out of staying up late and snacking, this may prove to be a habit worth revising.
I can see why it may be ill-advised to eat late at night. Is there a better time for me to snack?
Actually, yes! In fact there are health benefits that result from snacking periodically throughout the day. A study done by Hatori et al compared the feeding patterns of mice upon the development of obesity and metabolic disease. In the study, mice were designated to one of two groups. The first group was enabled to eat ad libitum, representing disruptions to the normal feeding cycle, while the second group was restricted to eating at specific times throughout the day. Both sets of mice were served diets equal in fat content and caloric value.
The results showed that the mice who were forced to eat at designated times during the day ended up presenting with improved nutrient break down and utilization. More importantly, the researchers found that the mice who ate at specific times throughout the day were protected against obesity, hyperinsulinemia (elevated insulin levels), inflammation and exhibited increased levels of motor function.
Although we cannot directly translate these findings performed in mice to humans, they suggest that while eating late-at-night could increase ones propensity towards developing chronic disease, there may be protective effects inherent in eating meals on a temporal schedule. The mechanism of this protective effect may involve the prevention of large insulin spikes via the consumption of multiple small meals scattered throughout the day.
This evidence is starting to come together for me, but that doesn’t change the fact that I am still hungry at 1am! What can I eat?
First, it is interesting to note that in a study that examined the eating patterns and health outcomes of early risers and late sleepers, that late sleepers ended up going to bed later in the evening and therefore snacking later into the night (past 8:00pm). They found that amongst the 52 participants, those who were categorized as late sleepers and ate later into the night had higher fast-food, full-calorie soda, and lower fruit and vegetable consumption than those who were early risers. This suggests that sources for late night snacking tend to be whatever is quick and accessible, and as a result, usually of low nutritional value.
By recognizing this common trap that late-night snackers tend to fall into, we can correct our own snacking habits for those times when we so desperately need that midnight snack. Let’s take a look at which foods provide the optimal combination of satiety and energy density so that we can optimize the benefits while reducing the damaging effects of late night snacking.
Studies that examined the influence of portion sizes upon weight management, elucidate the fact that the best foods to eat to facilitate weight management are those that have a low energy density, that induce satiety and that reduce energy intake. By eating low density foods that fill us up, we can satiate our hunger without packing on too many calories. As suggested by Ello-Martin et al, foods that fit this criteria are primarily fruits and vegetables.
So, when you’re on your last string looking for a late-night snack to help get you through the final page of that practice test, the research suggests that your best decision would be to grab some produce – in moderation (it is late at night after all).
Happy snacking, and happy studying!
Keep in mind
We cannot assume that late-night snacking is the sole contributor towards developing chronic disease considering that there are a whole slew of factors that influence our health status including hereditary factors, level of physical activity, environmental exposures, lifestyle, and eating habits to name a few. That being said, maybe the next time you go to grab a late night snack you will take a minute to pause and think about your health!