Actually, Matt, numerous clinical studies have shown mulberry leaf helps stabilize post-meal blood sugar spikes (through carbohydrate absorption), very important since these fluctuations are often the leading cause of complications from diabetes. Check out articles (do a web search) by Lee Zhong, M.D., Ph.UCLA
Seriously tho... I've never used them. If you can't say "NO" and not pick something up that's loaded with sugar, a little tablet is not going to help.
Kraken said it.. Willpower is what you exercise here... not spending money on a placebo.
However... if you crave something sweet post workout, natural peanut butter, a piece of fruit, or even a spoonful of honey could satisfy your sweet tooth and give you the benefit of being a healthy carb.