The evidence
What the evidence does — and does not — show
The ingredients in MetaMorphX have been studied individually; the finished formula has not. That is the single most important sentence on this page, and everything below is an attempt to be specific about it rather than to gloss over it.
African mango has the most directly relevant literature of the seven actives. A systematic review of randomised controlled trials in the Journal of Dietary Supplements found that the available trials reported reductions in body weight, but judged them small in number, short in duration and methodologically weak, and concluded that the evidence was not convincing (Onakpoya et al., Journal of Dietary Supplements, 2013). Those trials also used doses and preparations that are not necessarily the same as the 300 mg on this label.
Green tea is the most studied plant in the group and the most sobering. A meta-analysis in the International Journal of Obesity found that green tea catechins with caffeine produced a small effect on weight loss and weight maintenance, and that habitual caffeine intake blunted even that (Hursel, Viechtbauer & Westerterp-Plantenga, International Journal of Obesity, 2009). A controlled trial in the American Journal of Clinical Nutrition had earlier shown that a catechin-rich green tea extract raised 24-hour energy expenditure by about four per cent — a real effect, and a small one (Dulloo et al., American Journal of Clinical Nutrition, 1999).
Raspberry ketone is the weakest link. The finding that made it famous was an animal and cell study of anti-obesity action in Life Sciences (Morimoto et al., Life Sciences, 2005); there is no comparable body of human trial evidence, and a rodent result is not a human result. Apple cider vinegar has one small randomised trial in obese Japanese adults reporting modest reductions in body weight and body fat over twelve weeks (Kondo et al., Bioscience, Biotechnology and Biochemistry, 2009) — one trial, in one population, at a vinegar dose far larger than a powder inside a blend.
Then there is the structural limit. Six of the seven actives sit inside a 900 mg proprietary formula, so the label does not tell you how much green tea extract, caffeine or raspberry ketone a serving contains. Without those amounts, no study dose can be matched to this product, and nobody — including us — can tell you whether a serving reaches the amounts used in the trials above. The NIH Office of Dietary Supplements reaches a similar conclusion about the category as a whole, noting that the evidence for most weight-loss supplement ingredients is limited and that few have been shown to produce meaningful, lasting effects.
None of that makes MetaMorphX a bad purchase; it makes it a modest one. The reasonable expectation is a supporting role in a routine built on food, movement and sleep — not a substitute for any of them, and not a treatment for any medical condition.
