Curvy, it turns out that the capsaicin is just a very strong local diuretic, which doesn't mean that the creams other ingredients don't have any actual fat burning abilities. Because of the strong diuretic effect, I'd say you'd lose a lot of inches quickly but then experience a major plateau after the "excess" water is gone. Any further decrease would come from fat burning, and would take a lot more time. I can't tell you exactly how many inches you'd lose or how long it would take.
I just want to be perfectly clear, I don't think it's been anywhere near proven that the topicals I mentioned burn fat. I just think they're the only method of spot reduction that actually has a plausible mechanism. There's still an amazing lack of solid evidence. I only even considered them, because I don't believe there are any other plausible ways to spot reduce fat. Curvy, btw, the following is not directly aimed at you. I'm just "getting it out there"
Personally I would love for someone who's using at least one of these topicals for waist reduction to do an experiment on thigh girth at the same time. Yohimbine seems the most likely to work, so I'd hope they'd choose that one. They could start the little "experiment" by measuring both thighs with a tape measure at multiple points (maybe top middle and bottom) and take an average for each thigh respectively. Of course, the average will probably be different from their ACTUAL thigh girth at any of the points, but that doesn't matter. Measuring at multiple points is just meant to be a way to work around individual measuring mistakes, but I don't know if it'll do much to eliminate bias in the final measurements after treatment. After they've done that, they should apply the cream to only one thigh for at least 3 months. Then, hopefully, they'll do another measurement of both thighs and compare. It would be even better if they had a friend take the measurements without telling them which thigh is which. After that, they should wait a week without using any cream, to give the treated thigh a chance to rehydrate fully. Then they should measure both thighs a third and final time (or better yet, ask their friend again). If the difference between the two thighs disappears in the final measurements, than we'll know that, at least in their case, it only had a diuretic effect, and didn't actually burn any fat. That's hardly scientific, and it only applies to one person, but for me that'd be more than enough evidence to give up on this idea if it didn't show results.
I've considered doing this myself, of course, but I won't even bother with the cream until I've lost a whole lot of my extra body fat, and by then I may not even need it. I'm not holding my breath until anyone actually tries this, but it seemed worth mentioning.