TLDR: Fasted cardio of moderate duration for 45min to 1hr with a dose of L Carnitine or hydroxycitrate should increase fat burning with a 2-4 hr post exercise fast.
Abstract
From the standpoint of promoting fat loss, the chief benefits of aerobic exercise are attributable to fat oxidation during exercise and a post-exercise reduction of respiratory quotient. The ability of exercise to selectively promote fat oxidation should be optimized if exercise is done post-absorptively (preferably during morning fasting metabolism), if caffeine and possibly hydroxycitrate/carnitine are administered prior to exercise, if the exercise regimen is of moderate intensity and prolonged duration, and if no calories are ingested for several hours following exercise. A simple mathematical model is presented which delineates the factors that determine daily fat balance during exercise training. This model clarifies the crucial importance of low-fat eating if exercise is to have an optimal impact on fat stores. As a complement to aerobics, resistance exercise can benefit dieters by helping to preserve lean mass and metabolic rate in the face of a persistently negative caloric balance