This is the pick that follows the evidence to its logical end: the single most reliable, best-tolerated 'appetite suppressant' available over the counter is protein, and a quality whey is the easiest way to get more of it. Reviews of controlled trials (Astrup 2013) show whey lowers short-term appetite and raises the gut hormones that signal fullness — and in real life, a 24 g scoop or a high-protein meal simply keeps you fuller for longer than any herbal pill on this list, while protecting muscle in a deficit.
Optimum Nutrition's Gold Standard is the category benchmark: banned-substance tested, clean-mixing, and excellent value per gram. The only reason it's #3 rather than higher is framing — it works by anchoring meals and crowding out less-satiating food, not as a stand-alone pill, and the calories have to fit your deficit. Use it that way and it beats most of the products marketed specifically as appetite suppressants. Here's the full breakdown.