GMAT Strategy

Well, there's not really going to be a simple answer to this one. Will have to post in multiple segments, as I'm on a tablet.

Caffeine:
Different people have VASTLY differing levels of (a) sensitivity and (b) tolerance to caffeine.
You probably have at least a vague sense of how caffeine affects you. However, you may want to keep a "caffeine journal" in which you record the following parameters:
* Amount of caffeine ingested
* Source
* Time of day
* Hours of sleep the previous night
* Food eaten with the caffeine source
... and in which you record the following results:
* Time it takes the caffeine to "kick in"
* Feeling of alertness / increased attention, at that point (subjective scale of 0-10) at that point
* Feeling of restlessness / hyperactivity / nervousness, at that point (0-10)
* Feeling of hunger at that point (0-10)
* Approximate time at which you feel the peak effect of the caffeine
* Same three 0-10 ratings at that point. (If your adrenal system is working properly, your hunger score should be 0, 1, or 2 at this point, even if you haven't eaten much.)
* Approximate time at which you first feel a "crash" or "fade"
* Same three 0-10 ratings at this point.

That seems like a lot of data, but, if you collect them over just 1-2 weeks, you'll have a pretty good idea of how to optimize your caffeine consumption.
If your test is coming up soon, you may as well just keep the journal at approximately the same time of day when you're going to take the test, and save the more exhaustive analysis for later.
The time of day makes a HUGE difference -- the same amount of caffeine that makes me reasonably alert at certain times of day will make me immediately go to sleep at others -- so being even a couple of hours off will make the data much less meaningful.

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As for beverages themselves, Red Bull is pretty weak sauce, with only about 80 mg of caffeine in a can (about the same as you'd get in a 20-ounce bottle of Mountain Dew). It has about the same amount of caffeine per ounce as other "energy drinks", but the ridiculously small can means not much of a kick. (The can is small to increase profit margins, obviously, but also because Red Bull is a mainstay in bars -- they want to avoid the legal trouble that has befallen Four Loko and so on. Anyways...)
Make sure you do your homework here. For instance, a medium Starbucks brewed coffee has as much caffeine as 4 cans of Red Bull, or about 10 cans of Diet Coke. So, yeah. Journal. Do it.

Sugar:
You should avoid sugar. (Honestly, if you are over 16 years old, you should pretty much not eat sugar ever again in your life -- except perhaps after especially intense workouts -- but that's another discussion for another day.)
Eating sugar kicks up your insulin levels, with two main effects:
1/ Sluggishness and lack of alertness (= the "rest and digest" syndrome -- the opposite of "fight or flight"),
2/ Intense hunger. If you eat sugar, you'll be objectively more hungry than you'd be if you ate nothing at all. (Try a controlled experiment if you don't believe me.)
The worst part about the insulin-induced hunger is that it tends to kick in 1-2 hours after you eat sugar, which means you're going to get nailed right in the middle of the test. Ugh.

Oh yeah, and, if that's not enough to convince you, the whole idea that sugar provides extra energy ("sugar high") is completely false. There's no such thing as a "sugar high" at all; any such effect from candy is probably just a confounding effect from the caffeine present in chocolate. So, basically, there are no benefits to sugar at all -- none whatsoever, not even a little bit -- unless your gmat exam comes directly after a huge workout. (I don't recommend that, since big workouts tax the brain as well as the body.)

Incidentally, there's some evidence that a big workout 10-12 hours before your test, followed by sufficient sleep, will actually allow your brain to "supercompensate" and last slightly longer than usual. Worth a shot.

So, what should you eat?

To avoid having this post get interminably long -- and because I'm not going to be available for the next week or so to respond to posts -- I'm just going to split this into 2 possibilities.

IF YOU HAVE A BACKGROUND OF LOW CARB DIETING:
(not necessarily a hugely extensive background, but at least, say, a month or so)
Eat a medium-sized meal with 50-70% of calories from fat, 20-30% of calories from protein, and the rest (20% or less) from "slow" carbohydrates like potatoes or sweet potatoes.
Between the quant and verbal sections, eat a pack of almonds or peanuts.

IF YOU DON'T:
Eat a medium-sized meal with about 30-50% of calories from fat, 30-40% from protein, and the rest (30% or less) from "slow" carbohydrates like potatoes or sweet potatoes.
At breaks, eat almonds/peanuts and "slow" carbs. Portable "slow" carbs are hard to find, but edamame (Japanese soybeans) and carrots are a decent choice here.
Maybe eat some brown rice crackers. Do not eat white bread, white rice, or white just about anything.

Remember, food is not going to make you alert. (Quite the opposite -- people tend to be most alert when they're somewhat hungry.) Alertness is going to come from sleep and stimulants such as caffeine.
What you're trying to do with food is (1) fuel the brain -- the reason why you're eating here in the first place -- and (2) try to level out "high" and "low" feelings as much as possible (aka regulating insulin and blood sugar). These suggestions should help there.

I recommend that you eat a sensible meal before you go to the center. Something with protein. Then bring along 3 or 4 snacks that have some protein and complex carbohydrates. A Cliff Bar might be a good example.

Clif Bars -- no.
A Clif Bar has less protein than a corresponding amount of white bread. It also gets something like 40% of its calories from pure sugar. Just say no.

Clif Bars are for sustained muscular energy -- of the "I just hiked uphill for 2 hours and I have no glycogen left in my muscles" variety. I.e., they are designed to help you restore physical aerobic energy stores to depleted muscles. Obviously that's irrelevant here (your brain doesn't rely on glycogen).
For keeping your brain humming along during a test like the gmat, a clif bar would be an absolutely terrible choice. You'd actually be better off fasting.

The best during-test snack is nuts, specifically almonds or peanuts. If you are not at all accustomed to low-carb dieting, you should also throw in some carrots, edamame, or, if you're desperate, brown rice crackers. (If you don't immediately know the answer to "Do you have experience with low-carb dieting?", then the answer is no.)

Good luck.

dentobizz wrote:I have a question:If someone is feeling drained out after attempting the Quant section,then isn't it advisable to consume a snack that contains simple carbs during the break since the brain easily utilities simple forms of sugar (glucose,fructose,etc)to produce energy quickly?
This can have a temporary benefit-to help the test taker get past the final verbal section in the last 75 mins.

Well, the best answer is "Experiment and find out what works for you." For most people, though, this wouldn't be a good idea.
First, as you pointed out yourself, the goal is to fuel 75 minutes of relatively low-energy output. (It's not low-energy for the brain, but, relative to what muscles consume during intense physical exercise, there's just no comparison.) A huge hit of sugar released into your system all at once isn't going to last that long.
Second, simple sugar is not going to "give you energy quickly", unless (a) you are hypoglycemic and your blood sugar is perilously low, and/or (b) your body is drained of glycogen (i.e., you've just been exercising intensely). I'm assuming (b) is not true. If (a) is true, then you're diabetic and presumably know how to manage that already. So, yeah. Unless those things are true, eating simple sugars will lower your level of alertness, by flooding your blood with insulin and preparing the body to "rest and digest" (and store fat).

Again, though, these things vary from person to person. Sugar is definitely worse than making sure your body is fueled by reasonably slow-burning foods -- but just how much worse depends on the person. For instance, I personally "crash" if I eat anything containing more than about 10 grams of sugar, but I know people who aren't much affected by eating an entire cupcake. So, it won't be good, but it may not be as bad for you as for some others.

jaichil wrote:If only someone could tell this to Food Network channel. They keep showing all those dessert shows that make us crave for some.

I know this comment isn't entirely serious, but, a serious response nonetheless:
If you eat a low-carbohydrate, sugar-free diet for 3-4 weeks (or a ketogenic diet for 2 weeks), you should stop feeling those cravings after sticking to the plan for that much time. You'll get to a point where you look at those things and just say, "eh."