As Karin suggests, the majority of so-called “fat burning” supplements are untested and unregulated with regard to efficacy, ingredient content and safety.
Without reservation, I do not recommend taking any of them.
As you review exercise biochemistry recall that fatty acids are oxidized in the mitochondria of various tissue cells, the greatest volume of which are in skeletal muscle. The most effective way to increase “fat burning” is to increase the energy (ATP) demand in exercising muscles, especially the large muscles, through both vigorous cardiovascular exercise and progress resistance training. Progressive resistance training, as Joanne suggests, will likely lead to an increase in lean body mass which increases the RMR.
Keep in mind, as well, that sustained, accelerated aerobic metabolism in the mitochondria depends on the presence of an adequate supply of the end anaerobic metabolite of glucose, pryuvate. So consistent consumption of high complex carbohydrate foods, minimal simple sugars, to ensure adequate glycogen packing in the muscles is essential for maximum “fat burning.”
Further, it’s essential that you consistently consume plently of fluids, since water is one of the major by-products of aerobic metabolism. Among its many uses, adequate water is necessary of the packing of glycogen in muscle cells.