Is there any proof that vibrating belts cause weight loss?
There hasn't been any conclusive clinical studies that have found that vibrating belts, or any vibration exercise for that matter, can definitely help promote weight loss. Sadly, most studies have been done on full body vibration training, so some of the references I point to may not be specifically about vibration belts, but the mechanisms of each method are basically the same.
A review of several studies1 on vibration exercise in general, including the use of vibration belts, found that vibration exercise was not very efficient in burning fat. It wasn't found to be very good at promoting weight loss or changing the body composition at all (ie: building muscle). One study did show possible signs that vibration exercise and vibration belts can burn fat, but overall, the rate at which fat is burned at when using a vibration belt or other form of vibration exercise is low. There are some possible benefits of vibration exercise, such as higher oxygen intake. This review did not provide fully conclusive results, though.
Another review of many studies on whole-body vibration training2 found similar results, though they did point more in the favor of vibration exercise having benefits. The review states in its conclusion that:
[Whole-body vibration training] appears to be associated with three pathways involved in weight loss: inhibition of adipogenesis and reduction of fat mass, increased energy expenditure, and increase in muscle mass. After analysing the literature, none of the results for the proposed pathways are consistent, and indeed are often contradictory.
This review shows more positive results than the other review I mentioned that vibration training may promote weight loss, especially when used in conjunction with other exercises meant to help you lose weight. Vibration exercise does appear to be safe, though, so it can be used with a weight loss diet and exercises to help promote weight loss. Though this review was about whole-body vibration training, vibration belts work in a similar fashion, so it is likely that vibration belts may produce similar results.