To see how your energy levels dip, let's look at how energy works. The energy in your body is stored in packets called ATP as well as phosphocreatine, which are made up of a number of chemicals including a sugar called ribose, adenine (which used to be called vitamin B4), and derivatives of B vitamins. Ribose serves as the lumber of your energy-producing house, while other substances help support it (like hammer and nails). What is inside your cells (nutrients and genes) and other substances (hormones and chemicals from nerves and from your brain, etc.) act like fuses and switches to control the power factory you have. Your mitochondria and their component ribosomes take that ribose, sugar, and helper B vitamins and use electron transport to crank out ATP your energy packets. Once you have enough ATP, your body can crank out activities. Now, if you blow the fuse that allows you to produce ATP through infection, hormonal dysfunction, not getting enough sleep, have a diet that diverts energy rather than stimulates it, or many other causes your body produces energy inefficiently, using all its energy to, well, produce and store energy.
But ATP is only part of the body's energy portfolio. Even if you have plenty of ATP, you also need abundant blood flow to provide your body nutrients and take away waste products and that comes down to doing the things that help keep you arteries dilated and your blood pumping. What's good for your heart and arteries, in essence, is good for your energy levels, too. For example, nitric oxide that short-lived gas lining your arteries and breathing tubes and in your brain that rapidly changes according to your diet and activity level helps open up your arteries and lung passages to improve blood flow and increase the transfer of oxygen.
Problems with these systems really contribute too all energy deficiencies, yet the onset, cause, and treatments of lack of get-up-and-go are hard to nail down. You know when your feel slow and low, but it's hard to pinpoint what exactly is tripping you up or if it's just a normal part of running through the rigors of life. While fatigue, lack of sleep can explain other problems, the truth is that when put together, this constellation of symptoms makes it hard to navigate through our daily lives.