To the best of my knowledge there is no reputable study or report confirming this. Individual responses to L-Carnitin (or TRX2) surely depend on the bio-rhythm, metabolism and life-style of the customer. I'd say you should try this for yourself. The time of intake is variable, i.e. TRX2 can be taken at any time of the day. The only non-variable is consistency: TRX2 works with your metabolism and need to be taken regularly over a prolonged period of time in order to achieve positive results.