This week, we highlight how celebrities, such as daytime television star Holly Willoughby, are often used in the ads for dodgy weight-loss products without being asked.
How does it work?
Holly Willoughby is considering legal action after noticing that a weight loss company used her image without her permission.
The advert for ULTRAPur Wild Raspberry Ketone capsules shows a younger Holly in a bikini, holding a beach ball.
It's shocking to think a company would use an image of a famous face such as Willoughby, who has recently lost weight, without asking them first.
But such underhand tactics are common in the shady world of "miracle" dietary supplements and weight loss cures - many of which have no positive effects at all.
Common scam products to look out for include metabolism-boosting pills, fat or carbohydrate blocking pills, herbal weight loss teas, diet patches and body wraps - some of which can even be dangerous for your long-term health.
How can I avoid being caught out?
Do the promises made in an advert sound too good to be true? If they do, it's probably a scam.
So be wary of claims that you can, for example, lose a stone in two weeks, or completely change your body without altering your diet. For sensible weight loss advice, talk to your GP instead.
I've been defrauded. What should I do?
You are unlikely to get your money back if you buy a weight loss product that does not work - although you may be able to take advantage of the "guarantees" offered by certain companies if you return a product within the predetermined timeframe.
You can, however, report scams of this kind to the police via Action Fraud on 0300 123 2040, so that action can be taken to prevent others being taken in.