The Catch-22 of Losing Fat.
This article focuses on the often misunderstood and
widespread practice of how people try to get rid of
excessive fat.  It also describes the difference in
how the body burns energy — e.g. carbohydrates vs fats.
The following article will hopefully give some understanding of how our body stores fat and how it gets rid of it.
Unfortunately, information like this is often obscured by many sources, including the manufacturers of so-called health products, who have an ever-growing economic stake in such health issues.  In other words, don't expect those basic facts about weight loss to be disclosed by any energy supplement dealer or at your local health club.
First, let's define and differentiate two categories of energy; carbohydrates and fats.  They belong to two very different energy groups — carbohydrates belong to the "fast energy group" — while fat is in the "slow energy group."
When the caloric fat intake exceeds the amount of fat burned (for example, during daily activities) the body looks for places to store it.  Certain animals have dedicated storage places for the fat.  For instance, camels have large humps on their backs.  But humans store fat in a more arbitrary fashion — it's usually packed in "undisturbed" body areas which are not exercised on a regular basis.  Fat is dense and concentrated, and takes a long time to store and a long time to shed — "slow energy."  On the other hand, carbohydrates are packed easily and are immediately accessible, i.e., they are quickly disposed — "fast energy."
To function, the body needs a constant supply of energy.  However, the order of energy consumption is well defined; the body will not burn any fat until the level of carbohydrates is low.  Perhaps this is a known fact.  Although most of us learned about fat and carbohydrates in school, but evidently very few people think about what this adds up to.  Even less understood is the process of getting rid of the packed fat.
People, who would like to lose fat, often engage in an unfortunate, but very common practice; they consume energy supplements such as PowerBars before a workout and Gatorade during it.  So, what's wrong with that?  Well, nothing's wrong with it, unless the purpose of working out is to lose fat.
Those energy supplements are usually so filled with carbohydrates that they will supply the body with energy for an entire workout.  In the end, when those carbohydrates are finally burned, and when the body becomes "tired," most people feel as though they've done a decent workout.  But, unfortunately, they have not yet touched any fat.  All the energy which has been burned during such a workout has been the fast energy (carbohydrates), i.e., no fat.  To make things worse, after such a workout, most people understandably feel hungry and will reward themselves by eating, making the entire process a Catch-22.
When the body suddenly feels heavy and tired during a workout, it indicates that the carbohydrates have been used up and that the fat has started to burn.  In other words, the only way to burn fat is to continue to exercise after the carbohydrates have been depleted.  Therefore, the best and most efficient time for a workout is in the morning, before any energy intake (that goes especially for the fast energy).  Before and during the workout, it's best to drink water, and nothing else.
Here is an example, to clarify the above and to show how deceptive and misleading the manufacturers of workout equipment are:  A couple of years ago, a San Francisco Bay Area science news broadcaster received an abdominal workout tool for Christmas.  He was not a fat person, but the fat on his body seemed to be stored in his abdomen (which is a very common fat storage area for men).  He decided to use the "machine" and follow its directions thoroughly, to test the promise of "flat abs in a month."  The result?  The pictures of his belly before and one month after using the machine looked exactly the same; the belly was just as big as before.  The only difference was that the stomach was much firmer, having converted much of its fat to muscle.
This is a very common mistake.  In this case, the news broadcaster would have been better off if he'd exercised other areas of his body that he wanted to enlarge, rather than the area where the fat was stored.  He then would have burned off the slow energy reservoir (his fat belly) while building muscles in those other areas.  This would have created a slim abdomen with lean muscles — the initial purpose — instead of just maintaining the size of his belly.
In short, do not consume any food or energy supplements before or during your workout; and do not directly exercise the area(s) whose size you'd like to reduce.
The Catch-22 of Losing Fat.