The easiest way to evaluate this is to have a web- server somewhere, login via ssh through the tor-tunnel from your machine to the web-server and use tcpdump on the web-server to check if there are any incoming datapackets originating from your machine.
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The claims for weight loss are nothing short of outlandish and there is real science that suggests the whole thing is a hoax. Studies that claim to have found weight loss were carried out on animals. Studies involving humans are for the most part badly designed.