Sometimes, even after a solid eight hours of shut-eye we're still yawning at work.
According to their latest video, if you know the number of hours you're sleeping isn't a problem, the second most common cause of fatigue is lack of exercise and a poor diet.
"Study after study has found adults who began light exercise a few times a week reported more energy after six weeks," the video says.
"People who exercise more regularly also report sleeping better, even though studies show they aren't sleeping any longer."
Contrary to popular belief that coffee makes you feel wide awake, being over-reliant on caffeine can also make you feel sleepy.
This is because caffeine blocks the compound adenosine in your brain, which normally accumulates during the day and makes you sleepy at night.
"Consuming coffee or energy drinks less than six hours before bed can ultimately affect your sleep quality," the video explains.
"As a result, people who don't use caffeine often report feeling less tired in the morning."
Being dehydrated could be another reason why you don't jump out of bed ready to seize the day.
Studies have found that having a deficiency of water in the body leads to tiredness and difficulty concentrating. This is because your blood thickens, which slows down nutrients and oxygen getting to your muscles and organs.
If you're unsure if you're getting enough water, check out your pee. If it's darker than pale yellow, it's time to pour yourself another drink.
While it's important to drink enough water to fight off fatigue, drinking alcohol could have the opposite effect.
While alcohol might make you fall asleep faster, your quality of sleep will be much lower than usual, making you feel tired during the day.
Of course, your mental health also plays a big part in how energised you feel. If you're suffering from conditions such as anxiety, depression or stress you're likely to feel more drained than usual.
Such conditions can cause both physical and emotional fatigue and the quality of sleep you're getting may be affected. Talk to your GP if you're concerned about any mental health issues.
Other than that, if you're fed up of yawning in your morning meeting, a few lifestyle changes could make all the difference.