Ever get up for an early flight and by the time you get to the airport, you find yourself absolutely starving?
You wouldn’t be alone, science suggests.
According to an intriguing body of evidence, our finely tuned appetite clock goes out of control with unusually early starts, causing us to reach for high-calorie snacks.
Some scientists have even suggested that this phenomenon could explain obesity in people with often erratic schedules, including those who travel frequently.
A highly influential paper published in 2013 found that participants’ appetites reached a nadir at 8am – suggesting that waking up even an hour earlier could cause a slight increase in hunger pangs.
Harvard researchers found that appetite is lowest when you wake up and peaks around evening.
If you find yourself voraciously hungry throughout the day, it can be a good omen to think about your sleep habits and make sure you’re eating balanced meals.
In the studyTwelve volunteers were closely monitored for thirteen days by experts from Harvard University in a dimly lit laboratory without clocks, so they had no sense of time.
The researchers monitored their meals, sleep and wake times and monitored changes in their appetite.
They found a ‘robust’ hunger rhythm each day – with participants’ appetites reaching their lowest point when they woke up, around 8am, and their highest point in the evening around 8pm.
However, Professor Steven A Shea, the director of the Oregon Institute of Occupational Health Sciences who was part of the study, told DailyMail.com: ‘The 8am time in our study represents the average wake time based on the internal circadian rhythms of the volunteers. ‘
Based on their findings, people will generally be least hungry immediately after their normal waking time. So if you usually wake up at 7 a.m., you’re probably least hungry around that time each day.
It’s not clear exactly what causes this 24-hour cycle, but it probably has something to do with our hormones.
Hormones such as leptin, which helps control appetite, ghrelin, which helps control fat storage, and insulin, which regulates blood sugar levels, all fluctuate in your body throughout the day.
These all form a sort of complex chemical cocktail that reacts to the food we eat throughout the day to give us energy and tell us when to eat more.
A 2019 study from Brigham & Women’s Hospital in Massachusetts found that people’s ghrelin levels and appetite increased at night, similar to the Harvard study.
Other research from the University of Geneva suggested that people who are resistant to the effects of leptin in their bodies may have more trouble regulating their appetite and are more likely to become obese.
Of course, there are other factors outside of your body rhythm that can influence how hungry you feel when you wake up.
The number of hours of sleep you get is especially important.
Getting less than six hours of sleep can put your body out of sync with its natural hunger rhythm and you may have a larger appetite during the day, study from the University of Berkeley.
The study found that sleep-deprived people craved high-calorie foods more than those who got a full night’s sleep.
They suggested this was because the lack of sleep made the part of the brain that controls appetite less active, making people want to eat more.
Strong cravings can also cause you to choose less well-rounded meals, and the quality of the meals you eat is another important factor in your appetite, according to Michelle Routhenstein, a preventive cardiology dietitian and founder of Entirely Nourished Routhenstein.
For example, if you’re sleep-deprived and wake up hungry, you may want to quickly grab something low in nutrients, like a plain muffin, she said.
This doesn’t have a lot of complex nutrients for your body to process, meaning you’ll burn through it relatively quickly and will likely be hungrier for the rest of the day, Ms. Routhenstein said.
Eating a balanced breakfast — which includes protein, healthy fats and complex carbohydrates — should keep you feeling full longer, she said.
If you do this in addition to consistent sleep, your appetite will likely remain consistent.
To get the most out of your day and avoid feeling too out of balance with your appetite, Professor Shae recommends keeping things rhythmic.
“The most important thing people should do is sleep eight hours, on a regular schedule and eat regularly,” he said.