California is preparing to restrict sales of certain muscle building supplements and weight loss products to people younger than 18. Gavin Newsom signed the legislation, known as AB 2030, on Sept. 28.

The law covers over-the-counter diet pills and dietary supplements marketed for weight loss or muscle building. It is scheduled to take effect on Jan. 1, 2027.

California officials framed the measure as a safeguard against products that could pose health risks. “Nonprescribed, medically unapproved products may cause dangerous side effects,” the governor’s office said in its announcement.

The office also warned that the contents of supplements may not always match what consumers expect. “Products can be mislabeled or contaminated with substances such as steroids.”

Under the law, access will be restricted when supplements are “labeled, marketed or otherwise represented for the purpose of achieving weight loss or building muscle.” The wording makes a product’s marketing and presentation central to whether the restrictions apply.

The legislation says courts may consider whether a product contains creatine, green tea extract, raspberry ketone, garcinia cambogia or green coffee bean extract. The presence of one of those ingredients does not create an outright ban on every product containing it.

The law does not prohibit all creatine products. Instead, restrictions depend on how a supplement is labeled, advertised and marketed to consumers.

An exception applies when someone younger than 18 has a prescription for an over-the-counter diet pill or a dietary supplement intended for weight loss or muscle building. The measure therefore focuses on nonprescribed access to covered products.

The governor’s release cited research indicating that nearly one in 10 adolescents have used these types of products. It also referenced studies linking over-the-counter diet pill use to a sixfold greater likelihood of receiving an eating disorder diagnosis within three years.

Questions remain about precisely which products will fall within the measure’s boundaries. The announcement does not specify whether whey protein or creatine products are included in the sales restriction.

Businesses that fail to comply could face financial penalties. Sellers that violate the law will be subject to civil fines of as much as $500 for each violation.

The American Herbal Products Association, which is based in Maryland, released a statement opposing AB 2030. “Lacking any scientific justification, AB 2030 casts a shadow over safe, beneficial products,” said Robert Marriott, the association's vice president of regulatory and government affairs.

The organization contends that the scope of the legislation is unclear. It also noted that protein products are not explicitly exempted, adding another point of concern about how the restrictions will be applied.

The Center for Science in the Public Interest, based in Washington, D.C., publicly supported the legislation and helped sponsor it. “Manufacturers of these products often prey on kids and teens with deceptive claims that lack any scientific evidence,” said Jensen Jose, a regulatory counsel at CSPI.

Dr. Sigrid Wolf, a pediatric sports medicine physician at Lurie Children's Hospital of Chicago, recently said evidence supporting benefits from creatine products among teenagers is limited. “In some cases, they might even be dangerous,” Wolf wrote in an article published on HealthyChildren.org.

Wolf, a member of the American Academy of Pediatrics' sports medicine committee, also described potential adverse effects. “Creatine can come with negative side effects such as weight gain , dizziness, nausea, vomiting and diarrhea.”

She further warned, “Studies show that many supplements contain harmful substances that go undetected.” Rather than relying on such products, Wolf recommended prioritizing nutrition, training, sleep and hydration.

The conflicting responses reflect the central dispute surrounding the new law. Supporters point to possible health dangers and unsupported marketing claims, while opponents argue that the measure could sweep safe and beneficial products into an unclear regulatory framework.

Fox News Digital reached out to Newsom’s office for comment. The restrictions are set to become enforceable when AB 2030 takes effect at the beginning of 2027.