There are two big goals in the fitness industry; lose fat and build muscle. Both are antagonist principles in that one requires a calorie surplus and the other requires a caloric deficit. Chances are slim that you'll be able to accomplish both simultaneously (aside from those who are just starting out in fitness or those who are on very, very advanced type of plans).
You'll always get your best results if you can put forth all your effort and focus on one solitary goal, go hard, and then switch gears when you're ready.
That said, understanding the process of lipolysis, that is, how the body burns fat, will help you further along in your goal of fat loss.
Lipolysis is the breakdown of fat stored in fat cells. During this process, free fatty acids are released into the bloodstream and circulate throughout the body.
Lipolysis can be defined as the process in the body of breaking down stored triglycerides (or triglycerides in the blood for food we've just eaten), into two main components, glycerol and fatty acids.
In order for this to occur, an enzyme called sensitive lipase (HSL) must be present and in order for it to be active, there is a series of intracellular reactions that occur. It is these intracellular reactions where most supplements have their effects.
Another key element in the process of lipolysis is that of insulin. Insulin's main role in the body is to act in an anabolic manner, producing complex molecules from those that are simpler in form.
Keep in mind, however, that anabolic in this situation does not always necessarily mean muscle-building anabolic. While definitely insulin is a key contributor of muscle tissue growth and development, when insulin is present in a situation where there are more calories consumed than needed at any given moment, it will also be anabolic in terms of fat tissue.
When this happens, the body will begin manufacturing triglycerides. When insulin is absent in the body combined with a hypocaloric diet, it is then those free fatty acids will be released from the fat cell and fat loss will occur.
Stimulation Of Lipolysis
Along with the role that insulin plays, there are other hormones that will also come into the picture during lipolysis. Epinephrine, norepinephrine, glucagon (which is antagonistic to insulin), and adrenocorticotropic hormone will all work to induce the lipolysis process to take place.
Again, this is another area where supplements can come into play. By increasing the concentration of these hormones in the body, you will see a greater increase in the process of lipolysis occurring, thus helping the fat loss process along.
Do note, however, that even if these hormones are present, you still must be in a caloric deficit. Regardless of what supplement you are on, if you consume more calories in a day than needed to maintain your body weight, the body has to do something with this excess.
It can either form new muscle tissue (which is highly likely if you have been weight training), but there is a limit to how much new muscle can be built at any given time. After it's maxed out its muscle development, fat accumulation will begin to occur.
Getting The Fat Loss Process Going
So, your job to get the fat loss process going can be seen in a series of steps.
First, you must consume fewer calories than needed to maintain your body weight. Regardless of the types of macronutrients you eat and the percentage they make up in your diet, if you are eating more than you are burning, you're not going to be losing fat.
Second to that is working to control insulin so that it works with you rather than against you. How do you do that? - by timing your carbohydrates correctly.
Insulin is both good and bad; it's good in the fact that its presence is going to help the glucose you eat from carbohydrates get into the muscle cell, replenishing muscle glycogen so that you can recover faster between your workouts and build new muscle tissue.
It's bad on the other hand because if it's in high concentrations during the rest of the time, it's going to promote fat gain, assuming excess calories are present.
By ensuring you are in a calorie deficit, you'll really get ahead of the game in making sure additional body fat is not added.
But further, it's a good idea to try and focus the majority of the carbohydrates you do eat in your hypocalorie diet around the workout period. This is when your body needs them the most and will most effectively be able to replace that muscle glycogen.
Realize that it's not carbs per se that makes you gain body fat - it's an intake of carbohydrates continuously through the day in the presence of excess calories.
Where Stimulants Come In
Finally, we need to look at where stimulants come into the picture and how they can aide your process. As noted above, some stimulant products are going to serve to increase the concentrations of the hormones in the body that help trigger the lipolysis process.
Some supplements, Biotest 'Hot Rox' for example, will also promote a healthy metabolic rate. Since the thyroid is responsible for your natural metabolic rate, promoting this will therefore support the fat loss process.
Other supplements, Nutrex Lipo 6 for example, contain synephrine, which is an adrenergic amine that will stimulate certain receptors to increase the release of adrenaline and noradrenaline, which as discussed above prompt the lipolysis process to take place.
So, there are a variety of factors at play when it comes to fat loss. This is just a very brief overview of what occurs, in reality, there is a much more intensive cellular process that is occurring and can be altered due to a number of situations (what percentage of body fat you are currently at, what type of training you are doing, etc).
Overall though, if fat loss is your goal, you want to look into the supplements that will help with the lipolysis process as well as ensure that caloric deficit is being met. Once those are established, then you can begin to look into other nit-picky factors that may have a small effect.