GLP-1 pioneer Jens Juul Holst weighs promise and pitfalls of new weight-loss injections

The scientist behind the gut hormone breakthrough that paved the way for today’s blockbuster weight-loss injections has set out both the promise and the risks of the drugs in a frank conversation with physicist Jim Al-Khalili.

Jens Juul Holst, Professor of Medical Physiology and Biomedical Sciences at the University of Copenhagen, described how medications hailed in many quarters as "miracle drugs" for obesity and diabetes work by replicating the hormone GLP-1. The hormone signals to the brain that a person has eaten enough and prompts the pancreas to release insulin — a mechanism that underlies the self-administered injections now used around the world.

The hormone was discovered and decoded thanks to years of work by Holst, whose research laid the groundwork for the current class of treatments and earned him a string of major accolades. While the therapies’ rapid rise has transformed treatment options, Holst noted that their success brings difficult questions.

Among them are concerns over side effects, the risk of weight regain after stopping treatment, an emerging black market in the drugs, and their cost and accessibility. He also pointed to signs that GLP-1-based medicines might offer benefits beyond obesity and diabetes, though he stressed that such possibilities require further research.

Holst said his hopes for GLP-1-focused science include deeper understanding of how these hormones act across the body and how to tailor treatments to patients’ needs. But he acknowledged that ensuring safe use, fair access, and realistic expectations remains as important as the scientific advances themselves.