The FDA doesn't approve supplements (they don't approve food either - no "approved" signs over the spinach display or in the cereal aisle), but may require that they carry warning labels. You have to watch those. It defies logic, for example, to give kids a vitamin that says "keep out of reach of children" because they can overdose!
Most supplements should be made with ingredients on the GRAS list (Generally Recognized As Safe). My concern with something that has a limited use recommendation is, why? If it's a stimulant, then there's risk there (like too much caffeine, those terrible energy drinks and so on). Is it nourishing you? If not, there's a quick weight loss, the body goes into starvation mode, and then the metabolism slows down and weight stays on.
There are no clinical trials that I am aware of that show this as an effective weight loss ingredient. Personal stories - you will find this for most anything that makes people conscious of what they are eating.
But what's in this product? Who makes the one you are planning to buy? (Anytime there is a new fad, every company jumps on board to make a quick buck until the next fad comes along, and there's never any follow-through and there are few if any safeguards.) What are the differences in the manufacturing processes of different companies? Is it even made in the US under near pharmaceutical grade conditions? Does the manufacturer at least have the FDA Good Manufacturing Practices designation? Is it made someplace with no controls at all? Is it non-GMO?
A lot of weight gain seems to be from processed foods depriving our bodies of needed nutrients. ("Enriched flour" for example - it's stripped of its nutrients and then a few vitamins are thrown back in. There's nothing enriched about it!) So we crave nutrients, we eat more, and we still don't get what we need. When they put together panels of physicians and nutrition experts to figure out what we'd need to eat in the typical American diet to get enough of every nutrient, it works out to 4000-5000 calories per day! A prescription for weight gain!
Nutrients, vitamins, minerals, trace elements, etc. all have to be consumed together for each one to have its necessary "partners" for metabolism and absorption. Single ingredients are never the key to any major health issue.
Based on my work as a nutritional counselor, I've seen a few things in the food science world that DO help, but they involve clinical studies, high absorption nutrition, and a full complement of compatible nutrients in a synergistic blend that are also bioactive (survive the digestion process and are highly effective at getting directly to the cells). Vitamin pills (and mineral supplements, etc.) are absorbed somewhere around 20-25% depending on how they are made - with 75-80% going down the toilet, literally. You've probably seen all those studies of municipal water supplies and sewage treatment plants, and you can ask anyone in the septic pumping business - filters and tanks are full of undigested pills.
Effective supplementation is the surest way to weight loss as well as better health and immune system support because you get all the nutrients your cells need without excess calories. Supplements cannot be based on the old RDI levels either - they have to be based on optimal levels - what do your cells need in order to thrive, not just to keep you from getting rickets and scurvy. I only recommend things that have research behind them, clinical data, the FDA GMP seal, ingredient quarantine and pre-testing as well as testing during and after manufacture, and I look for US government patents on entire formulas (not just an individual ingredient) which means the whole thing has been proven safe and effective.