Hydroxycut SX-7 Black Onyx Review

If you’re looking for the new Hydroxycut Black (not under the MuscleTech brand), check it out here.  Hydroxycut SX-7 Black Onyx is the most recent fat-burner released under the Hydroxycut/MuscleTech brand.  It features some standard fat-burning ingredients that appeared in it’s predecessor, Hydroxycut SX-7, as well as some new entrants…

Hydroxycut SX-7 Black Onyx


Green Coffee Extract

In recent years, Green Coffee Extract has become a staple in weight-loss supplements for its ability to reduce carbohydrate uptake, thus mimicking the effects of a carb-restricted diet. There has been a fair amount of research conducted specifically investigating Green Coffee Extract on bodyweight in humans and most of it is quite promising.

A 2007 study, published in the “Journal of International Medical Research”, found that 12 weeks of Green Coffee (450-500mg Clorogenic Acid) supplementation resulted in a reduction (6.9%) in glucose absorption in healthy volunteers. Researchers also noted average weight loss of 5.4 kg (almost 12 lbs) over the duration of the study in the group receiving the Green Coffee Extract.

A 2006 study, this time using a smaller dose of Green Coffee Extract (yielding 140mg Chlorogenic Acid), found no such weight-loss benefit over a 12 week period. The obvious difference between these two studies is that the dose of the first (positive) study was about 3 times the dose used in the second (negative) study.

A 2012 study found that adults who consumed GCE (containing about 315mg Chlorogenic Acid) daily lost an average of 8kg with the average reduction in body fat being about 4%. However, this study has since been retracted for reasons unknown.

The fact that different doses have produced different results indicates that Green Coffee Extract is only effective when enough Chlorogenic Acid is present. Hydroxycut SX-7 Black Onyx contains 200mg of GCE, yielding 90mg of Chlorogenic Acid. So, in order to actually make a difference, at least 3 servings daily would be necessary.


Caffeine has become a standard ingredient in fat-burners because of its role in releasing Noradrenaline, a neurotransmitter that inherently burns fat. Although this mechanism can certainly kick start fat-burning in the short-term, prolonged Caffeine consumption (by itself) generally results in tolerance build-up so the effects become less potent over time. This was demonstrated in a 1992 study in which 24 weeks of Caffeine intake (200mg/day) failed to induce weight-loss in humans. For Caffeine to be an effective fat-loss agent, it generally must be combined with other stimulants such as Yohimbine (also present in Hydroxycut SX-7 Black Onyx).

MuscleTech lists the exact dose of Caffeine at 145mg per serving, a relatively low dose compared to what’s out there. However, considering the Hydroxycut SX-7 Black Onyx is a multiple serving type formula, 145mg per serving seems more or less appropriate.

Coleus Forskohlii

Coleus Forskohlii is an Ayurvedic herb which has been studied (though not extensively) for its potential as a non-stimulant weight-loss agent and natural testosterone booster. The active component, Forskolin, has been demonstrated to increase Cyclic Adenosine Monophosphate (cAMP), the result of which is an increase in the rate of fat-loss.

A 2005 study, published in the “Journal of the International Society of Sports Nutrition”, found that 25mg Forskolin twice a day for 12 weeks was able to prevent weight gain compared to the control group in overweight women.

Another 2005 study, the subjects of which were overweight men, found that the same dose (25mg) was able to favorably influence body composition (i.e. less fat, more lean mass), which corresponded with an increase in testosterone over 12 weeks.

A more recent 2011 study noted a roughly 2.5% decrease in BMI after 2 months of supplementation. Ultimately, Forskolin may certainly result in weight-loss or at the very least, prevent weight gain. These effects may be more apparent in men, as an increase in cAMP also increases testosterone, which inherently burns fat and increases lean muscle mass.

Unfortunately, MuscleTech does not disclose the amount of active Forskolin in this particular extract, just the amount of total Coleus. Assuming that this particular extract is standardized for 95% active Forskolin, Hydroxycut SX-7 Black Onyx contains an effective dose, but that is a pretty big assumption. We have to believe that, if the formula did yield a truly effective dose of Coleus, MuscleTech would make that clear.


Theanine is seriously under-utilized ingredient in stimulant-containing fat-burners, probably because it tends to be expensive. Theanine and Caffeine is one of the few combinations that can actually be considered synergistic, rather than merely additive.

In a 2008 study, published in “Nutritional Neuroscience”, researchers investigated the cognitive effects of a combination of Theanine and Caffeine compared to Caffeine alone on various measures of cognitive performance. Participants received either 50mg of Caffeine or 50mg of Caffeine and 100mg of Theanine before completing various tasks including word recognition, visual image processing, and attention switching. While Caffeine was able to increase alertness and accuracy during the attention switching tasks, the combination of Caffeine and Theanine was able to improve both performance and speed, while reducing the subjects’ susceptibility to distraction.

Another 2008 study from “Biological Psychology” found that, while 150mg of Caffeine increased alertness and improved (decreased) reaction time, adding 250mg of Theanine further improved reaction time, alertness, and decreased the number of headaches reported from Caffeine.

The combination of Caffeine and Theanine was further put to the test in a a 2010 study from “Nutritional Sciences” and another 2010 study published in “Appetite”.

As mentioned above, Theanine tends to be expensive, and that may have been what caused MuscleTech to under-dose it for the purposes of Hydroxycut SX-7 Black Onyx. The formula contains about three times more Caffeine than Theanine, so although there is still some benefit to be obtained here, we can’t say with any certainty (based on the research) that the two are downright synergistic. Theanine may simply serve to reduce some of the negative effects of Caffeine.

Salvia Miltiorrhiza

The use of Salvia miltiorrhiza is yet another instance of MuscleTech attempting to be a first-mover, and to the company’s defense, there is some decent preliminary research on this one.

A 2006 study, published in “Phytotherapy Research”, found that Salvia increased Dopamine release in mice. These results were replicated in another 2006 study from “Neurochemical Research”, also in mice.

Currently, no human studies have been conducted specifically to investigate these effects, so it appears MuscleTech is reaching a little with this one. For that reason, we wouldn’t necessarily consider Salvia a major ingredient in Hydroxycut SX-7 Black Onyx, but it may contribute somewhat the overall “sensory experience”.

Yohimbe Extract

The primary active component of Yohimbe (Pausinystalia Yohimbe) is Yohimbine, the mechanisms of which are discussed in this article.

A 2006 study showed that while there were no increases in strength, supplementation induced fat loss in athletes (soccer players).

MuscleTech lists the amount of Yohimbe at 20mg, yielding roughly 1.2mg of Yohimbine. This is a pretty low dose, even for Yohimbine, but assuming multiple servings are taken throughout the day, some fat-burning is bound to occur.


Beta-Cryptoxanthin is a carotenoid, high levels of which can be found in Satsuma mandarins. It has long been suspected of encouraging weight-loss/preventing weight-gain but, and recent Japanese studies indicate there may actually be something to it.

A 2011 study from “Frontiers in Neurology” found that Beta-Cryptoxanthin administration repressed body weight and abdominal fat-tissue in male mice, and improved libid metabolism and energy consumption. These results were replicated in another 2011 study, published in the “Journal of Agricultural and Food Chemistry”, which attributed the effects to Beta-Cryptoxanthin’s ability to prevent adipocyte (fat-cell) hypertrophy (growth).

While more (human) interventions will be needed to further understand how Beta-Cryptoxanthin can be used for weight-loss, the preliminary research is quite promising. MuscleTech is certainly a first mover on this one, and while we wouldn’t consider this particular ingredient a “game-changer”, it may very well contribute to the overall efficacy of Hydroxycut SX-7 Black Onyx.

The Bottom Line

While MuscleTech’s claim that Hydroxycut SX-7 Black Onyx is “The Most Hardcore Weight Loss & Ultimate Sensory Experience” is bit of a reach, the formula does have some fat-burning potential. For noticeable results, multiple servings may be necessary, as some of the non-stimulant ingredients are definitely under-dosed on a per-serving basis.

Still not sure which fat-burner is right for you? Check out our Top 10 Fat-Burners List!

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