I have previously stated that I believe transdermal prohormones to be the most effective supplements ever to hit the market. That statement must now be amended. Transdermal prohormones are indeed the most effective MUSCLE BUILDING supplements ever to hit the market. But, topical fat loss products have the potential to be an even bigger overall breakthrough in the never ending quest to improve body composition.

There are four areas that need to be addressed in regards to topical fat loss products and so called "spot reducers" in general. First, one needs to distinguish between the products that are merely diuretics and those that the manufacturer (assuming they have a brain) actually thinks might significantly reduce body fat. Second, we have to have an understanding of the andrenergic system, which is primarily what these products attempt to manipulate in order to aid lipolysis Thirdly, we must have an understanding of transdermal/percutaneous delivery, in order to understand why a topical formulation could present advantages vs. orals, as well as to understand why every product of this kind currently on the market, other than LipoDerm-Y, fails. Within this category there are 2 issues -- getting adequate amounts past the skin barrier and localizing its distribution to adipose tissue. And, finally, there is the issue of Yohimbine HCl vs. yohimbe. After reading this, you should have an understanding of why true "spot reduction" is physiologically quite possible, as well as enough information to make an informed decision as to which products can and cannot accomplish it.

Fatloss Agents vs. Diuretics

Assuming we are not preparing for a photoshoot or competition, a product that merely acts as a diuretic rather than significantly aiding actual lipolysis is basically worthless. "Cutting Gel" belongs in this category -- its active ingredient is aminophylline:

Aminophylline is a xanthine derivative, similar to caffeine, which is not a particularly potent fat burner. In rat studies, it has shown good thermogenic properties due to blockade of adenosine receptors (which provide one of the negative feedback mechanisms for catecholamine induced thermogenesis) and inhibition of phosphodiesterase (which degrade cyclic AMP) -- but this is at extremely high doses, which would kill a human, so it is not applicable (1,2). At therapuetic doses, only adenosine blockade occurs, which will act to increase norepinephrine levels (3)-- but as you will see norepinephrine stimulates alpha 2 receptors (bad) in addition to beta 2 receptors (good) -- and in stubborn fat, alpha 2's outnumber beta 2's (4).

Like caffeine, it is a good diuretic (5), which would account for the girth loss in the study they reference, which did not measure actual fat loss (6,7). One study did look at fat depth after use of an aminophylline cream, and no difference was found vs. control (8). As a local diuretic, it might be effective, but as a true fat loss agent, it quite likely is not.

Precontest, such a product could be extremely beneficial if it would truly localize the water loss, as it would allow one to get rid of extracellular water with out the total body dehydration produced by drugs such as Lasix -- thus, one could have fuller muscles, less cramping, etc. I am not particularly familiar with the physiology of diuresis, as I have not researched it to any great extent, so I don't know if it could actually be localized.

Products such as LipoDerm-Y, Impact's DermaLean, and S.A.N.'s LipoBurn (basically any of the products with yohimbine and a handful of other ingredients) fall into the latter category. They are intended to manipulate the adrenergic system, thus, theoretically, such products could cause true localized fat loss if formulated properly:

The Adrenergic System: Introduction

One of the major contributors to body weight homeostasis in the human body is the adrenergic system. There are two types of adrenergic receptors, alpha and beta, as well as subtypes of each -- and depending on which are activated, lipolysis (breakdown of fat) can be either stimulated or inhibited.

The most well-known adrenoreceptors to bodybuilders are the beta receptors. These can be divided into subtypes 1, 2, and 3 -- and it is through these receptors that drugs such as the ephedrine/caffeine stack and Clenbuterol exert their effects. While Clenbuterol acts directly on beta 2 receptors, ephedrine exerts its effects indirectly by stimulating the release of norepinephrine (NE), the body's primary endogenous thermogenic hormone. Unlike Clenbuterol, NE is not selective in its binding. In addition to binding to the beta 2 receptor, it also binds to both alpha receptors, as well as the beta 1 and 3 receptors. It is in regards to its binding to the alpha 2 receptor that yohimbine comes into play.