Meta's Health and Wellness standard exempts health clubs and fitness services from its 18+ rule, but an ad selling weight loss, such as a fat-loss challenge, must target people 18 and over. For adults, weight-loss ads may show people using the service and its impact if they clearly state the time taken. Meta rejects statements of inferiority about appearance, close-ups pinching fat, and promises of specific outcomes in a set timeframe without qualifiers.
Meta also bans copy that implies you know the viewer's health or body ("Overweight? Join today"); write about the program instead. On Google, body shaming or negative framing puts an ad in the "Imposing negativity" sensitive category, which blocks your remarketing and Customer Match lists for it.