A harmless electrical current is passed through your body. Since muscle is loaded with water the premise is that it will take longer for the current to travel through a fat person. Advantages: It's non-invasive and easy to do.

Drawbacks: Many variables affect the result which is often two high for very lean subjects and too low for very fat subjects. The results are often different within a 30 minute time frame.

Cost: $25-$50

Where you can get it: Health club; personal trainer; dietitian