GLP-1 medications, which mimic a hormone involved in appetite regulation, are powerful but do not eliminate hunger entirely, according to Dr Federica Amati, nutrition lead at Imperial College School of Medicine. The drugs are described as being approximately 1,000 times stronger than the body's natural GLP-1 production, leading to a prolonged feeling of fullness.
However, users may experience gastrointestinal issues such as nausea, constipation, diarrhoea, bloating, and vomiting. Dr Adrian Brown, an associate professor and specialist dietitian at University College London, notes these tend to occur during dose escalation and often improve over time. Preparing the gut with a plant-rich, high-fibre diet before starting treatment may help mitigate these effects.
The drugs can also lead to nutrient deficiencies if a person's diet is poor, as they substantially reduce food intake. Research indicates some individuals may not get enough vitamin D, vitamin B12, iron, calcium, and protein. Additionally, weight loss from GLP-1 medications can include up to 40% lean mass, making protein prioritisation and resistance training important to preserve muscle.
Weight regain is a significant factor when stopping GLP-1 medications, with studies showing people can regain about 60% of lost weight. One University of Oxford study found that individuals may return to their original weight within two years of stopping the medication. This suggests that for many, these drugs may be a long-term or lifelong treatment, similar to medications for high blood pressure or cholesterol.
Not everyone responds to GLP-1 medications in the same way, with 5-20% of people losing less than 5% of their body weight. These drugs are licensed for individuals with type 2 diabetes, obesity, or those who are overweight with weight-related health problems, and are not designed for purely aesthetic weight loss.