If Oprah, Serena Williams and Musk are recommending a weight-loss drug: who’s keeping an eye on what they say?

Once upon a time, there was a ban on direct-to-consumer advertising of medicines. To be honest, this was the case all over the world, except in the United States and New Zealand. But this made sense in the pre-social media era, because advertising has now migrated from the printed pages of newspapers and television adverts to the murky depths of the internet, and social media in particular. And here, celebrities of the calibre of Serena Williams , Oprah Winfrey or even Elon Musk , give you a wink, as if they were chatting to a friend or neighbour, and tell you about the wonders of the current best-sellers amongst prescription medicines (which are therefore supposed to be prescribed only by a doctor): those based on GLP-1. Of course, despite all his millions of dollars, Elon Musk cannot write a prescription, but his ‘advice’, once brought to the attention of your trusted GP, will easily turn into a prescription. In short, we are faced with a new, extremely powerful form of marketing that circumvents all boundaries, whether geographical or relating to current regulations on direct-to-consumer advertising of medicines.

This is the warning issued in the pages of the *New England Journal of Medicine*, where a group of researchers led by Nils Krüger, together with the renowned pharmaceutical policy expert Aaron Kesselheim, sets out in black and white a phenomenon that has taken centre stage in recent years: the promotion of medicines, whether consciously or not, by celebrities.

The most striking case concerns Oprah Winfrey, who, in March 2024, devoted a national television programme to weight-loss drugs, speaking openly about the benefits of semaglutide and tirzepatide, with the participation of consultants put forward by Novo Nordisk and Eli Lilly. A different, but equally telling, case is that of Serena Williams, winner of 23 Grand Slam titles, who in August 2025 recounted her experience with these drugs following childbirth in a social media campaign for the telemedicine company Ro, (stating that her body ‘needed’ them, without ever explicitly naming the active ingredient); but what caused a real scandal was the 30-second advert broadcast to the year’s largest television audience, during the Super Bowl half-time show last February, in which the tennis champion injected herself with a GLP-1-based drug, recalling how much good it had done her (“I’ve lost 15 kg, reduced my cholesterol by 30 per cent and cut my risk of cardiovascular disease by 70 per cent”) and was sure to mention that “the pill version of this medicine is now also available” (oral semaglutide for obesity has been available in the US since late 2025, at an introductory price of $149 a month).

Elon Musk, too, has spoken publicly on several occasions – and in enthusiastic terms – about his own use of these weight-loss drugs, whilst Tom Brady (a former American football player) is even an investor and chief wellness officer at a telemedicine company that markets them. And so, day by day, the line between personal opinion, sponsorship and outright advertising is becoming increasingly blurred.

Faced with the proliferation of VIP endorsements, the Food and Drug Administration responded last September by issuing a series of warning letters. Novo Nordisk and Eli Lilly were accused of presenting, via Oprah’s programme, a misleading picture of the safety of their medicines, downplaying the risks. Ro’s campaign featuring Serena Williams, whilst sharing similar characteristics — benefits emphasised, risks virtually absent — did not, however, prompt any action from the regulatory agency. The authors of the article highlight this difference in treatment as symptomatic of a system that is struggling to keep up with the times.