Como aminoácido en el metabolismo de la grasa, la carnitina sirve para transportar la grasa a la mitocondria.
El cuerpo saca toda la carnitina que necesita de la dieta, y a menos que se sea deficiente de ella, suplementarse no vale para nada más que para mearla en su exceso.
La L-carnitina como suplemento para la pérdida de grasa es teoría. No hay un sólo estudio que lo demuestre claramente, más bien todo lo contrario. Lo más que hay es que aumenta en poca medida la masa múscular y aumenta la resistencia, y como consecuencia a eso, la pérdida de grasa en algunos. Pero no de por sí.
Quizá valga en su forma pura, pero eso no es lo que se encuentra en las tiendas de suplementación, que es una degradación de la misma y, encima, azucarada. En esas condiciones, la L-carnitina no afecta en nada al músculo, y aun así tendrías que coserte a insulina. Mucho menos a la pérdida de grasa.
E incluso en el link que pones, la conclusión es que no hace nada y que cualquier el impacto es nulo.
Extraído del link:
Studies have consistently failed to increase skeletal muscle carnitine content either through oral supplementation or intravenous L-carnitine administration. Watcher et al (2002) fed 2 grams of L-carnitine twice a day for 3 months to normal people and failed. Similar studies by Barnet et al. (1994) and Vulkovich et al. (1994) demonstrated similar failures with oral feedings of l-carnitine for 3 months.
Extraído de The Protein Book de Lyle McDonald:
Of possible importance to strength/power athletes, two recent studies have found that l-
carnitine l-tartrate (2-3 g/day for 3 weeks) decreased the incidence of muscle damage with
high-repetition weight training (100,101); an even more recent study found similar effects
from either 1 or 2 grams (102). The same group showed that supplementation of 2 grams
of l-carnitine l-tartrate per day for three weeks caused an increase in the concentration of
androgen receptors (103); this might be expected to improve the adaptations seen to
resistance training in the long-term.
En fin, que para perder peso, que es seguro por lo que se está preguntando aquí, no vale.
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