There is no herbal extract. HCG is a hormone, not a herb.
Perhaps you meant the homeopathic pills? Those have a few things going against them...
1. There's no actual HCG on them.
2. Your body can't absorb HCG orally anyway, it has to be injected.
3. HCG doesn't help with weight loss in any way at all.
If someone takes them and loses weight, it's because they believe they've taken something to help, and this helps them feel more confident about sticking to good choices, which leads to weight loss. The pills themselves have nothing in them that can at all contribute to additional weight lost.