How the exact time you wake up can influence how hungry you are all day - even if you got your full 8 hours

Ever got up for an early flight and, by the time you get to the airport, you find you're absolutely ravenous?

You wouldn't be alone, science suggests. 

According to an intriguing body of evidence, our finely-tuned appetite clock falls out of whack with unusually early starts, making us reach for calorific snacks.

In fact, some scientists have suggested that this phenomenon could go some way to explain obesity in those with frequently erratic schedules, including those who travel often. 

A highly influential paper published in 2013 found that participants' appetite hit an a low at 8 am — suggesting waking even an hour earlier could see an cause a slight increase in hunger pangs.

The Harvard researchers determined that appetite is lowest around when you wake up and peaks around evening.

If you're noticing yourself voraciously hungry throughout the day, it might bode you well to consider your sleeping habits, and make sure you eat balanced meals. 

In the study, by experts at Harvard University, 12 volunteers were put under strict watch for 13 days in a dimly lit laboratory with no clocks, so they had no sense of time. 

The researchers tracked their meals, sleep and waking times and monitored changes in their appetites.

They found a 'robust' hunger rhythm each day - where participant's appetite hit its lowest point when they woke up, at around 8 am, and it's highest point at night around 8 pm.

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However, Professor Steven A Shea, the Director of Oregon Institute of Occupational Health Sciences who was part of the study, told DailyMail.com: 'The time of 8 am in our study represents the average waking time based on the volunteers internal circadian rhythms.'

Generally, based on their findings, people will just be the least hungry right after their normal wake up time. So if you usually wake at 7 am, you'll likely be least hungry around that time every day.  

It's not exactly clear what causes this 24 hour cycle, but it probably has something to do with our hormones. 

Hormones like leptin, which helps controls appetite,  ghrelin, which helps control fat storage, and insulin, which regulates blood sugar - all fluctuate in your body over a day. 

All these 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 peoples ghrelin levels and appetites increased at night, similar to the Harvard study. 

Other research from the University of Geneva suggested that people who are resistant to the affects of leptin in their body might have more issues regulating their appetite and more likely to become obese. 

Of course, there are other factors outside of your bodily rhythm that can influence how hungry you might feel when you wake up.

The number of hours sleep you get is particularly important.

If you get less than six hours of sleep, your body may fall out of sync with its natural hunger rhythms and you might have a bigger appetite throughout the day, research from University of Berkeley found.

The research found that people who were sleep deprived craved high-calorie foods more than those who got a full nights 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 might make you choose less well-rounded meals as well, and the quality of the meals you eat is another important factor in your appetite, according to  Michelle Routhenstein, a preventative cardiology dietitian and founder of Entirely Nourished Routhenstein.

If, for example, you're sleep deprived and you wake up hungry - you might grab something quick with few 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 likely be more hungry throughout the rest of the day, Ms Routhenstein said.

Eating a balanced breakfast - which includes protein, healthy fats and complex carbs - would make you fuller for longer, she said. 

Doing this on top of getting consistent sleep is likely to keep your appetite consistent.  

To get the most out of your day and keep you from feeling too off-balance with your appetite, Professor Shae recommends keeping things rhythmic. 

'The biggest thing that people should do is sleep eight hours, on a regular schedule and eat regular meals, he said.