The results of this study indicate that a weight loss supplement containing anhydrous caffeine, synephrine, tetradecylthioacetic acid, yerba mate extract, methylphenylethylamine, yohimbine, and hordenine is effective in increasing acute energy expenditure in young, healthy individuals. Ingestion of this supplement also resulted in significant elevations in heart rate and systolic blood pressure indicating a strong inotropic response to this supplement. In addition, acute ingestion of this supplement increased tension and confusion among subjects.
Comparisons between weight loss supplements need to be performed carefully considering the large variability seen in ingredients or different concentrations of ingredients. Previous research has shown that acute ingestion of caffeine, synephrine and other herbal ingredients in a coffee supplement significantly increased energy expenditure 12% among healthy, lean college students [6
]. In this present study, using a similar subject population the combination of anhydrous caffeine, synephrine and different herbal ingredients resulted in a 29% increase in energy expenditure. Although differences could be related to differences in concentrations of similar ingredients within each supplement, the difference between these studies is likely related to the differences in co-ingredients within the supplement.
Caffeine and herbal supplements have been shown to increase resting metabolic rate for up to three hours following ingestion [6
]. These effects have been shown in supplements combining caffeine with ephedra and black tea [10
], and with caffeine combined with synephrine, garcinia cambogia and chromium polynicotinate [6
]. The greater energy expenditure seen in this study compared to others is likely related to the additional ingredients in this supplement that have previously been found to enhance metabolism and therefore have a synergistic effect with known thermogenic ingredients such as caffeine.
Synephrine is a mild stimulant that comes from the fruit citrus aurantium
(bitter orange). It is the predominant alkaloid from this fruit, and is thought to stimulate fat metabolism [12
]. Hordenine is an alkaloid that occurs naturally in grains, sprouting barley and certain grasses, but it is also found in small quantities in citrus aurantium [22
]. When infused to horses it has been shown to increase respiratory and heart rates, however when provided orally no significant cardiorespiratory changes were seen [23
]. Other studies have suggested that hordinine can exert its stimulating effect by inhibiting norepinephrine uptake [15
]. Although human studies with hordinine are very limited, it is likely it works synergistically with synephrine to enhance the sympathetic response.
The elevated blood pressure and heart rate responses seen during the SUP treatment are similar to other studies examining weight loss supplements containing adrenergic amines [5
]. Synephrine is thought to increase lipolysis and minimize the cardiovascular effect typical of adrenergic amines [12
], however synephrine has also been shown to stimulate peripheral α-1 receptors resulting in vasoconstriction and elevations in blood pressure [25
]. Although synephrine ingested alone may not alter blood pressure, when ingested in combination with other active herbal ingredients does appear to elevate blood pressure and heart rate [5
]. The combination of synephrine, caffeine and hordinine used in this study appears to cause significant elevations in the cardiovascular response to supplement ingestion.
The trend towards a greater utilization of stored fat as the primary energy source, as evidenced by a lower RQ, in this study is likely related to the combination of yohimbine, yerba mate extract and tetradecylthioacetic acid. The precise concentrations of yohimbine and its metabolites in this supplement are not known, thus discussion concerning how these differences may have effected changes in fat mobilization would only be speculative. Yohimbine is a selective α-adrenoceptor antagonist that has been shown to be effective in enhancing lipid metabolism [16
]. However, the extent of yohimbine's effect may have been modulated by its various metabolites within the supplement. No differences in RQ between the groups were seen in the first hour following supplementation but significant differences were seen at hours two and three. This may be reflective of differences in α-2 adrenoceptor blocking potency and half-life between the metabolites of yohimbine [27
]. Although yohimbine is a more potent α-adrenoceptor antagonist than its metabolites, it is metabolized more quickly.
Yerba mate extract made from the leaves of the tree Ilex paraguariensis has been shown to suppress appetite and prevent diet-induced obesity in rats [28
] and humans [14
]. It is thought to cause weight reduction by delaying gastric emptying [14
] and its effects may be enhanced by caffeine [4
]. Although it is proposed to have several potential health benefits besides weight loss [29
], its role in elevating energy expenditure or increasing lipolysis is not well understood, and may be negligible. Tetradecylthioacetic acid has been shown to be effective in enhancing fatty acid metabolism [30
The addition of phenylethylamine as an ingredient was thought to enhance the mood of subjects using this supplement. Phenylethylamine has been shown to produce relief of depression among a clinical population, even in those that were unresponsive to standard treatments [18
]. An advantage in the use of phenylethylamine is thought to be related to the beneficial mood improvements seen without producing a tolerance often associated with amphetamines [18
]. The mechanism of its effect appears to be related to the stimulation of dopamine release [31
]. This may contribute to an improved mood state and has also been shown to potentially reduce appetite [32
]. In addition, phenylethylamine may also stimulate lipolysis through its ability to stimulate catecholamine release and delay reuptake [33
]. The results of this study indicate that phenylethylamine did not affect mood, but may have contributed to the greater reliance on fat as an energy source. Considering the various ingredients within this supplement, it is possible that the greater tension and confusion seen in SUP may have been a result of the adrenergic stimulants contained in the supplement.
In conclusion the results of this study indicate that following an acute ingestion of a weight loss supplement containing anhydrous caffeine, synephrine, tetradecylthioacetic acid, yerba mate extract, methylphenylethylamine, yohimbine, and hordenine leads to a significant increase in energy expenditure in young, healthy individuals. In addition, ingestion of this supplement stimulates elevations in heart rate and blood pressure for three hours, while increasing feelings of tension and confusion. Individuals who have been diagnosed with cardiovascular disease need to be aware of the significant cardiovascular effects resulting from use of this supplement. Additional research is warranted concerning the long-term effects of consumption of this supplement, and whether such supplementation can translate into weight loss or improved body composition.