When you eat matters as much as what you eat, authors say in new book

Welcome to GMA’s New Year, Best You. As we ring in 2019, we are sharing everything you need to start the new year strong. From keeping your New Year's resolutions going to Instagram-worthy meal prep to workout programs to eating plans to taking time for yourself, we have it all covered.

The foods we should be eating -- fruits, vegetables, lean protein, healthy fats -- are well-known, but many don't realize that the timing of when you eat affects how you feel and how healthy you are too.

The idea that timing matters when it comes to food is the focus of a new book, "What to Eat When," by Dr. Michael Roizen, chief wellness officer at the Cleveland Clinic, and Dr. Michael Crupain, chief of the medical unit at "The Dr. Oz Show."

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"Your circadian rhythm changes your metabolism throughout the day and it gets your body ready to eat the right thing at the right time," Crupian told "Good Morning America." "The job of your circadian rhythm is to get your body to do the right thing at the right time, so you want to align what you eat with when you eat it."

"Then you're really hacking your metabolism get better health, sleep better, to have more energy and to even help you lose more weight," he added.

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Crupain and Rozin shared with "GMA" what they learned while writing the book, from how long to wait to eat between meals to why they like to eat dinner for breakfast.

Get more tips on the science behind nutrition timing and how to eat when you're tired or stressed in this excerpt from "What to Eat When."

Here are the two basic rules for eating the When Way: (1) Eat when the sun is up, and (2) eat the majority of your day’s calories before 2 p.m.

These two actions, along with eating a healthy mix of macronutrients, will take your body to a good place, with better health, less disease, more energy, and lower weight.

Our goal is for you to make this style of eating your new normal. This allows you to take full advantage of chrononutrition: syncing your body’s clock with your eating schedule.

We also know that life is never normal. Stuff happens. Habits are threatened. And there are a zillion and one things that can derail even the best of intentions. The second definition of when refers to situational eating - what you eat when life happens. There are great benefits to adjusting the kinds of foods you eat to the situations you find yourself in, from a day at a baseball game to a genetic disposition to a chronic disease.

This information is based on scientific evidence that proves you can influence the health of your body through the macronutrients and micronutrients that you ingest.

WHAT TO EAT . . . When You’re Stressed and Hangry

When you eat the When Way, you’ll spend a fair amount of time boiling water—blanching those vegetables, whipping up a soup, hardening eggs. Anyone who’s watched a pot knows exactly how it works: stovetop on, tiny bubbles appear, then bigger ones, until—finally!— the water rumbles and is ready for action.

But what happens when your blood boils? When you get so mad or frustrated or hopped up on the injustices of the world that you feel like your head’s going to explode? Well, it’s kind of the same thing: Like the water in a pot, your blood rumbles and rages until you’re ready for some action.

Most of us have the ability to manage our emotions well enough that “some action” doesn’t involve fists (or worse). Unfortunately, though, “some action” can mean you’re ready to go 10 rounds with Mr. Häagen Dazs.

Once you tangle with a pint of Pralines & Cream, you may feel like you’ve lowered the temperature on your blood boil. But you wind up losing the big battle in the end. That’s the effect of acting out of “hanger.” You may temporarily numb, mask, or forget what set you off—but when you reach for an instant soother that hurts more than it heals, you’re ultimately doing much more damage to your body in the long run.

Think of it this way: Even if a truckload of chips stops your blood from boiling, all you’re really doing is turning the temp down to a stealthy simmer—a simmer that comes in the form of high blood pressure, high LDL cholesterol, high blood sugar, and more.

Now, we know what you’re thinking. It’s one thing to say skip the chips, but when you’re in the heat of the moment—and your brain is setting off the hangry fire alarm—you need to do and chew something immediately. There ain’t no time to whip up a bowl of minestrone when junior decorated your new walls with crayons, markers, or the goodies he found in his diaper.

Rule number one: Don’t go near a fast food establishment when you’re hangry. These restaurants use smells, images, and sounds to reel you in1,2,3—and these cues can trick you into eating more than you want or need.

When you’re hangry, you’re especially vulnerable to food cues like scents and aromas. The key is to keep your blood sugar balanced with foods that will bring your emotions to a low simmer, and keep you healthy to boot.

It’s no surprise that emotional eating is a real biological phenomenon. We see it play out in all kinds of ways, and theories abound as to why hunger and emotions go together like sweat and stink. For one, several parts of the brain, including the hypothalamus, thalamus, and insula, among others, deal with hunger. These areas can influence the way your body is aroused. (Arousal, for the record, can come in many forms; whether it’s positive, as with sexual arousal, or negative, as with anger, both your heart rate and body temperature will rise in these states.)

In addition, the physical state of hunger works as a sort of trigger that leads to an emotional response. For example, low blood sugar (caused when you’re hungry) has been linked to aggression and impulsivity, both of which can certainly play a role in a spur-of-the-moment rendezvous with a vending machine. Ultimately, though, hunger can seem to impair self-regulation, our own ability to make decisions with the executive function part of our brains.5 So, combining the two— hunger and anger—leads to the perfect storm of coaxing you to ditch the When Way and grab a Milky Way.

That begs the question: What to do? It’s not as if you can simply ignore everything that triggers intense feelings of anger, nerves, or frustration. But you can do two things to help take the edge off.

First, if you are able to stay satisfied during the day, it’s less likely that hunger will inhibit your impulses. This actually works incredibly well with our front-loaded way of eating. That is, if you’re satisfied with a generous breakfast and/or lunch, you’re less likely to feel the impulse to eat emotionally if something gets to you later in the day.

Second, it’s always wise to create your own emergency response system. Having healthy foods on hand—whether a bag of crunchy vegetables, a healthy, protein-rich bar (no added sugar or syrup or non–100 percent whole grains), or even a stash of turkey on 100 percent whole wheat that you can grab on the go—can get you through a wave of emotion.

An extra step: Mute your TV during advertisements or pick an alternate route from work so you don’t pass by your local fast food franchise. The “out of sight, out of mind” principle will help you stay healthy.

You can’t always control what life throws at you, but you can control what you throw down your gullet. Ultimately, emergency foods should have a little fiber, a little protein, and healthy fat to help alleviate hunger and to satisfy you in a very balanced way. And although avocado toast is a nice choice, it’s not always realistic in the heat of the moment.

Here are some other foods you can try:

MVPs: Roasted chickpeas are our favorite anti-hangry snack. They not only contain those good-for-you macronutrients, but they’re also an incredibly satisfying way to help you power through problems without the blood sugar spikes that can follow consuming processed snacks and refined sugars.

In fact, studies have found that eating legumes, like chickpeas, helps control blood sugar and hunger even better than animal protein.6,7,8 No, we don’t expect you to jump to the oven and roast up a tray of them when emotion hits—but they’re a great snack to prep ahead and keep on hand (plus, they are tasty cold as well).

To make roasted chickpeas: Dry the chickpeas by rolling them in paper towels, then spread them evenly on a baking sheet and sprinkle with a little extra-virgin olive oil and your favorite spices (if you like Indian food, they’re delicious with some curry powder, or try adding garlic, rosemary, and cayenne, the way Dr. R prefers them; you can also place the beans in a small bag with some extra-virgin olive oil with seasoning and shake till evenly coated, then spread on a baking sheet). Roast in the oven at 425 degrees for 30 to 40 minutes, shaking the sheet pan every 10 minutes.

Key Players: In a pinch? Pop in a microwavable pack of no-butter-added popcorn. Filled with fiber, popcorn keeps you full, and will satisfy that oh-I-need-to-crunch feeling. If you like, you can sprinkle in a bit of sea salt, cinnamon, Old Bay Seasoning, or even a dusting of Parmesan cheese and pepper for a savory, salty, and crunchy snack, all at the same time. Have a little more time? Skip the premade bags and try your hand at an air popper. Or place dried kernels on the stovetop with a tablespoon of extra-virgin olive oil, cover, and cook over medium heat, shaking the pot every 30 seconds until the popping stops.

Cut From the Team: It’s OK to engage in strategic dabbles with dessert, but your go-to food when you’re feeling mad shouldn’t be boxes of sugary treats. It doesn’t matter if it’s candy, cookies, ice cream, or doughnuts. Bottom line: The refined sugar will momentarily make you feel good (the sugar high), but you’ll crash hard afterward—and your body won’t have the much needed energy sources to get you over the next slump.

The Sub Shop: Mad Meals

SUB OUT… Doughnuts

SUB IN… Plain instant oatmeal mixed with some no-added- sugar nut butter will be incredibly satisfying and a little sweet. Plus, it’s filled with fiber to help you avoid blood sugar spikes and to keep you full longer. Add cinnamon if you like.

WHAT TO EAT . . . When You’re Fighting Fatigue

The world spends billions fighting fat. It spends billions more when you add “-igue” onto the phrase. We’re a tired bunch, for sure.

Trying to pinpoint the cause of fatigue is like trying to explain why your Uncle Lew still can’t figure out Facebook— darn near impossible. That’s because there are dozens and dozens of causes; some constitute the root of the problem, while others combine to produce mental and physical exhaustion. The reasons are myriad: not enough sleep, not the right foods, side effects of medication, hormonal issues, undetected conditions, not enough activity, too much stress, and on and on.

That’s why the root problem—not getting enough quality sleep and feeling like a big blob of gelatin in the morning as a result—has to be addressed at a deeper level by identifying potential causes or triggers of fatigue. But here’s a hint: Food is a major answer (after all, quite technically, food is energy).

Unfortunately, many of us turn to artificial or unhealthy stimulants to give us the spark we think we need. But in the end, they hurt us: Instead of raising and sustaining energy levels, these stimulants cause them to fluctuate like the stock market in a volatile economy. That’s a problem because it makes us eat even more unhealthy foods.

This is where much of our collective energy problem lies. When we feel tired, we look for anything we can find to help restore our energy levels. Our gut reaction is to crave sugar, which is our body’s most immediately available form of energy. And it works!

We get peppy and zippy and think all is well. But that simple-carb high is very soon followed by a simple-carb crash, which leaves us feeling even more fatigued than when we started. And the vicious cycle starts again.

Ultimately, we want you to use quality sleep, regular exercise, and stress management to help restore energy levels (all subjects for a different time). But we can also show you how to add food to your power-boosting arsenal.

For starters, the When Way of eating will be a huge advantage. Eating earlier helps keep your energy systems primed and revved throughout the day. When you do find yourself looking for boosts, focus your attention on two forms: the kind of energy that can give you a non-crash-worthy quick jolt, and the kind of energy that can sustain you for a long time. Here’s how to approach these.

YOUR FUEL TANK: KEEP IT FILLED

Water: Lack of water is one of the leading causes of fatigue. If you’re not well hydrated, your body uses resources to maintain water balance instead of giving you energy. We keep water by us all day and constantly sip it. We also recommend having a glass or two first thing when you wake up in the morning. And of course, you need more when you exercise. Drinking eight glasses is a good ballpark, but it’s also worth investing in a half-gallon thermos so you don’t have to worry about keeping count. Just finish the jug every day and you’ve got it.

Healthy fats: Fat is the most energy-dense macro, and most typical snacks mix it with simple carbs. These calorie bombs give you the up-and-down energy we talked about, plus help you gain weight. On the other end of the spectrum, healthy fats mixed with protein and fiber let you take advantage of the slow energy release fat provides without all the risks. That’s one of the reasons why unsaturated fats—like ones found in salmon, nuts, and avocado—are such a crucial part of the When Way. It’s probably also why avocado toast has become so popular as a breakfast food: It ensures you get some healthy fat and fiber at the start of every day.

Protein: Protein in lean meats (chicken, turkey, and fish) is excellent for energy; you can also get protein in beans and nuts. Having protein early in the day is also key.

YOUR PORTABLE CHARGER: QUICKER HITS

Coffee and tea: You already know these are staples of an energy-boosting diet. Both are great (and generally don’t give you the energy swings that sugar will), so it’s OK to have these caffeinated beverages provided you don’t load them with sugar or other heavy add-ons, like cream and flavored syrups.

First thing in the morning is fine. But our friend Dr. Oz likes to have some tea in the late morning, instead, before a natural slump may occur.

Reprinted with permission from From WHAT TO EAT WHEN by Michael Roizen, M.D. and Michael Crupain, M.D. Reprinted courtesy of NatGeo Books