Food Supplements?

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Hello,
Just wondering what peoples opinions are on food supplement pills like Guarana seed?
Ive started taking one in the day when i want to eat sugary things and junk basically, and this seems to stem the hunger pangs... Dont get me wrong i still eat a very healthy balanced diet, these are just to stem the urge to eat junk food!
Is this a good thing? should i stick to this as it works? JUst interested on peoples general opinion..
Thanks!!!