This is 911, need-to-know info only. To keep you focused on the big picture, I'll begin with an example at the extreme end of nutrient timing. If the average Joe followed the same diet as an Ironman triathlete, he'd likely have type 2 diabetes in a matter of months. Conversely, if someone tried to complete an Ironman on even the healthiest version of a low-carb diet, that person would either be forced to quit or die. This is not just because either diet would mean eating too much food or too little food. Different foods cause the body's metabolic process to react in different ways; and various activities should be fueled using various means.
Let's begin by looking at our possible fuel sources:
Are fuel only. They aren't stored in body tissue, only in the blood and liver as glycogen, which needs to be burnt off. They are essential for high-level functioning like running fast, lifting heavy things, and thinking. They are digested and put to use by your body very quickly. If you eat more than you burn, your body will convert them to be stored in adipose (fat) tissue.
Called the body's building blocks. Hence, you need them to rebuild tissue that breaks down daily. You digest proteins slowly, and at a certain point, your body just can't assimilate them. Therefore, it's important that throughout the day you eat foods that are high in protein.
Help regulate all of your bodily functions. They are dense and contain over twice the calories of proteins and carbohydrates. While they are vital for our health, it's easy to eat too much of them, which will result in unwanted fat tissue on your body. You digest fats slowly, and fats will also help slow the digestion of anything else you eat. Fats are also your backup fuel source, though they can't be put to use right away the way carbs can.
Categorized as a carbohydrate, it is not a source of fuel as it has no calories. It's the indigestible part of a plant and is of vital importance in your diet because it regulates the absorption of the foods you eat. It also helps us feel full. Most of us don't eat enough fiber, and that's a big part of the obesity problem.
Not really a food source but something we tend to consume. It has nearly twice the calories of proteins and carbs (though it lacks fuel) and digests rapidly. Its only healthy function is that it seems to make us happy. Studies indicate this is a good thing, as those who consume alcohol generally live longer than those who don't, but from a purely nutritional standpoint, it's not so hot because you're getting calories without any upside. Its use should be strategic and regulated for best results.
Now let's look at the various situations we face daily, at least on most days—hopefully.
This is when we're sedentary both physically and mentally. In a relaxed state, you burn very few calories because your body is engaged as little as possible, hence the relaxing.
When we're at work or school. Our bodies aren't moving, but our brains are engaged. The brain runs on glycogen, which is blood sugar fueled by carbohydrates.
Like mowing the lawn, cleaning the house, or going for a walk. This breaks down body tissue, so you're burning calories, but it's not intense work. Therefore, it can be fueled by your stored body fat. Your body tries to fuel its low-level outputs by mobilizing fat stores because this saves its limited glycogen for emergency situations.
Fueled by glycogen. When you really have to get after it, all sorts of hormones go to work, and your body burns its blood sugar. Body-tissue breakdown is rapid, and your stored blood sugar (glycogen) won't last much more than an hour.
A very active time. Deep sleep is where your body works the hardest to repair itself. You need nutrients to make these repairs, but it's better if you aren't mucking up the process with digestion. This is why you hear that you shouldn't eat too much at night. It's best to eat early to allow most of the digestion to happen while you're awake, thus allowing your body to use all its energy for recovery during sleep. It is worth noting here that it's better to eat before bed if you need the nutrients—don't skip them. Your body can't repair itself without nutrients, and recovery from breakdown is why we eat in the first place. Next, let's take a look at an important word you need to know: insulin.
Wikipedia tells us that insulin "is a hormone that has extensive effects on metabolism and other body functions, such as vascular compliance. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle, and stopping use of fat as an energy source." Okay, that's a little scientific, but look at all the things we've already referenced: hormone, glycogen, metabolism, and fat as an energy source. Even if you don't fully comprehend "vascular compliance," you can tell that insulin is something important in today's discussion.
Sure enough, it's the only hundred-dollar word we need to know today. Your body's insulin response is the main reason you want to eat certain foods at certain times, to do certain things.
Putting it all together
Now let's take what we've just learned and put it to use. For most of us, nutrient timing is pretty simple. The next thing to consider is what you're going to be doing or what you just did. As I said before, what you eat should be based on this. You've probably heard about the evils of sugar, or maybe even the glycemic index. Using the science of nutrient timing, you can turn sugar into something healthy because it's the only thing that transports nutrients into your blood quickly enough to be of service during and after hard exercise.
Essentially, sugar or other easily digested carbs (the less fiber the better) promote an insulin release. This speeds the transformation of carbohydrates into glucose in your blood. As your glycogen stores are depleted during exercise, recharging them with sugar minimizes the damage done by the breakdown of tissue during exercise. Therefore, sugar, the oft-vilified ingredient, is actually your body's preferred nutrient during times of excessive stress and tissue breakdown.
Pretty cool, huh? The bad news is that this miracle nutrient is not good for you when you're not doing intense exercise, which for almost all of us is most of the time. In fact, sugar's very bad for you because the insulin response that was so fabulous for you when you were bonking (glycogen depleted) is not so fabulous for you when you're sitting in front of the boob tube.
Remember this from the Wikipedia definition of insulin, "stopping use of fat as an energy source"? That's bad when you're sitting around. Remember how one of dietary fat's responsibilities is to fuel you during low-intensity exercise? Well, when sugar causes your insulin to spike, it cuts off that process. Now not only are you not burning body fat for low-level outputs, you're trying to force your body to use its glycogen. Double bad.
Unless you're exercising, sugar intake should be minimized. During these times—which is most of the time—your diet should consist of a mixture of proteins, fats, and complex carbohydrates. The latter are natural sources of carbohydrates that generally come with fiber, which regulates the insulin response. Whole fruit, a simple carbohydrate by definition because it contains fructose (a sugar), always contains fiber and, thus, can be treated as a complex carb. Fruit juice, and other such stuff, is processed; it, along with processed complex carbohydrates like white rice, can cause an insulin response, so these types of foods should be used more like sports foods than staples.
It's also important to note that combining all these different nutrients slows sugar's ability to incite insulin into action. Therefore, a little sugar like a dessert after a well-rounded meal is buffered by the meal. The calories and lack of decent nutrients (processed sugar is devoid of most nutrients, except for energy) still count toward your overall diet, but at least you don't have to worry about an insulin spike.
So the main point of this article is very simple. You should eat small, well-rounded meals most of the time. These should include some proteins, some fats, some fiber, and some carbs. During (only if it's a long workout) and after hard workouts, you should supplement your diet with sugar or simple carbohydrates. After this, you should go back to eating well-rounded meals again.
Sports nutrition has evolved this process even further. In nature, foods are generally slow to digest. Nature's great sports foods are things such as bananas and figs. These are sugary but still contain fiber and other nutrients. Science has found ways to make foods that are even more efficient during sports. These basically manipulate pH levels and process the sugars to speed them into your system. Outstanding when you need it. Terrible when you don't.
They've even taken this a step further by finding a ratio of other nonsugary nutrients (like protein) that can be transported by the sugar to give you a further benefit. Beachbody's Results and Recovery Formula uses this science. When you're bonking during a hard workout, it speeds nutrients that are essential for quick recovery into your system as quickly as possible.
I can't stress how important it is that sports fuels be used for sports performance only. Gatorade, soda, and all sugar candies (hey, no fat!) all function as the poor man's sports foods. Unfortunately, those perusing the Quick Stop generally aren't trying to fuel up after doing Plyo X, and therein may lay our obesity trend.
In case the topic is still a bit fuzzy, let's use the above logic on the examples in the intro: An Ironman athlete is doing intense exercise for 10 to 12 hours or more. During this time, that athlete is mainly burning glycogen, which is gone after an hour or so. The athlete burns stored fat, too, but this is limited in its effectiveness. To race, the athlete must replenish with sports foods because they contain the only nutrients that the athlete will digest fast enough to help. To complete an Ironman, especially at your physical limit, it may take 5,000 calories coming mainly from sugar.
This is a sports-specific diet only. Someone trying to eat that way during a viewing of the Lord of the Rings trilogy would be lucky to stay out of the emergency room. Conversely, if you tried to maintain a 25-mph speed for 8 hours on your bike while munching on raw spinach and lean steak, you'd bonk so hard you'd be praying to get yanked from the race at the first checkpoint. That should cover your 911 on nutrient timing. Next time, we'll move on to the topic of supplements. Are they magic pills, overhyped placebos, or something in between?