Why top executives swear by a 30-second morning habit anyone can adopt

Kat ColeKat Cole, president of FOCUS Brands, the parent company of Auntie Anne's, Carvel, and Cinnabon, wakes up a 5 a.m. every morning and drinks 24 ounces of water.
Huffington Post founder Arianna Huffington and former Birchbox Man chief Brad Lande both start their days with a glass of hot water with lemon.
Why are these execs reaching for water instead of coffee?
We asked Rania Batayneh, MPH, a nutritionist and the author of "The One One One Diet," about the potential benefits.
Here's why she recommends that everyone start their days with a glass of water:
1. Drinking water first thing in the morning immediately helps rehydrate the body.
The six to eight hours of recommended nightly sleep is a long period to go without any water consumption. Drinking a glass or two of water right when you wake up, however, is a good way to quickly rehydrate your body, Batayneh says. 
"Most people have their coffee first thing in the morning," she says. "Although it is a good source of antioxidants, it is also dehydrating. You can offset this with water."
2. Drinking water first thing in the morning increases your level of alertness.
"One of the biggest indicators of lethargy or low energy is that you are dehydrated," Batayneh says. "Because water aids in both body regulation and brain function, it is also closely related to balancing out our moods."
After a long period without anything to eat or drink, the first thing you consume in the morning can be a shock to the body. If that first thing is ice water, it will get the body working and "can boost your alertness and low energy levels," she says. 
3. Drinking water first thing in the morning helps fuel your brain.
When it comes to daily productivity, hydration is crucial. The human brain is made up of 73% water, Batayneh says, so staying hydrated is especially essential for maintaining optimal brain activity. It is, of course, a daylong process, but starting with a glass of water right away is a step in the right direction, she says.
"The mornings set the tone for the rest of your day," Batayneh says. "If you feel sluggish, it will reflect in your activity (morning workout), productivity at work, and even your routine with the kids."
4. Drinking water first thing in the morning can help you fight sicknesses.
When you're sleeping, your body is in repair and recovery mode, Batayneh says. During this time, your immune system is hard at work ridding your body of toxins. By drinking enough water, you can speed up the process in which your body flushes those toxins.
Aside from the brain, a majority of many of the body's other major parts, like the heart, kidneys, and lungs, is water, she says. Simply put, staying hydrated is a key ingredient in staying healthy. 
5. Drinking water first thing in the morning jump-starts your metabolism.
The essential carbohydrates and proteins that you consume on a daily basis are metabolized and transported by way of water throughout the body. Having a sufficient amount of water in your system will help fire up your metabolism, Batayneh says, and it can also help with your diet.
"When we are not adequately hydrated, we can mistake thirst with hunger, which leads us to eat more," she says. 
An earlier version of this post was published by Steven Benna.NOW WATCH: T. Boone Pickens' strict morning routine will inspire you to plan your days better