Adverts for weight loss tablets XLS Medical have been banned following 200 complaints that they promoted an unhealthy body image, especially among teenage girls.
The three ads on television, YouTube and video on demand featured two women exchanging text messages, with one saying that XLS Medical could help users lose up to three times more weight than dieting alone.
The second actress then looked in the mirror frowning and said: "I'll never fit into my holiday wardrobe," before the two were shown on holiday posing together for a photo.
The Advertising Standards Authority (ASA) received complaints from British Naturism and 198 other viewers that the ad was likely to appeal to under-18s because it used actresses of a similar age.
They also complained that the ad promoted an unhealthy body image.
Omega Pharma said the actresses were 24 and 29 and had a body mass index (BMI) within the guidelines set out in advertising codes.
It said the comment by the second actress was in line with the well-accepted concept that some consumers sought to adopt a healthier diet and lifestyle before going on a summer holiday.
The ASA said the woman's comment that she would "never fit into my holiday wardrobe" was likely to be seen by viewers as presenting her as needing to lose weight despite her already slim and healthy appearance.
It said: "We considered the models had a slim, healthy appearance but actress B in particular had been portrayed as having poor body image and confidence, expressed through her desire to lose weight ahead of her holiday and her belief and disappointment that she would not be able to wear the clothes she had already set aside for her holiday.
"We considered the combination of her already healthy, slim appearance and poor body image and confidence created the impression that weight loss was desirable."
It ruled that the ads must not appear in again in their current form, adding: "We told Omega Pharma to take care to ensure their products were advertised in a socially responsible way."
An XLS Medical spokeswoman said the company was disappointed with the ruling.
She said: "Across all of our communications we ensure that we represent a range of body shapes, ages and sizes to acknowledge where our consumers might be on their own weight loss journey. As part of ad development we work with an independent weight management consultant to ensure we deliver positive and appropriate messages.
"All XLS Medical products are certified medical devices approved by a notified body, and we are committed to providing healthy eating education and support. Our intention is never to cause offence, simply to highlight the variety of healthy weight-loss and weight-maintenance goals and motivations XLS Medical can support with."