Spot fat / cellulite reduction with a quality cellulite cream
A good topical fat loss cream is one that contains a high amount of several natural ingredients that stimulate fat release from your fat cells (just for the record, few such good fat loss creams exist). Your superficial fat cells constantly release or accumulate fat in reaction to contact with various substances that reach the fat cell. These substances can reach your fat cells either through the blood circulation (foods, hormones) or through the skin (creams).
If for example blood capillaries infuse glucose in the adipose extracellular fluid (the fluid that surrounds a fat cell), the cell will react by absorbing this glucose and converting it into fat. If insulin is infused at the same time, glucose absorption increases. This leads to fat cell enlargement - certainly not a good thing for local fat reduction.
If, on the other hand, adrenaline (the fight or flight hormone) is infused from the blood into the adipose tissue during to exercise (or during a fight with your partner!), the fat cell will tend to release fat. If caffeine originating from a cream is infused through the tissues and into the adipocyte extracellular fluid, it will stimulate the fat cell to release fat. If retinol is infused it will stimulate the fat cell to change it's function towards fat release and can even make the cell die off early (this process is called apoptosis). All these things lead to fat cell shrinkage or even fat cell early death - certainly a good thing for local fat reduction.
Since one biochemical pathway usually is not enough to produce the results you are after, your fat-releasing cream should ideally contain several ingredients that act via several pathways. And of course, those ingredients should be in high enough concentrations to make an impact on your fat cells. Otherwise the message will be subdued and the cells will react more to the insulin and the glucose and the saturated fat you are feeding them, rather than to the cream ingredients...
So there you have it - you need a cream with several fat-fighting ingredients in significant concentrations, combined with a diet poor in carbs and saturated fat that does not encourage your fat cells to grow (and ideally combined with some exercise that will give a helping hand to your cream in it's fight against the flab).
If these four conditions are met (multiple actives, high concentrations, low calorie diet & exercise), a cellulite cream can indeed help you lose local fat, a process called spot fat reduction. And as the name suggests, this reduction is small and localised, i.e. you cannot expect to lose pounds of fat, but rather small localised fat deposits and, of course, cellulite.