What are the risks of Glucagon-like peptide-1 (GLP-1) receptor agonists in patients with low body mass index (BMI) or underweight status?

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Last updated: May 27, 2025View editorial policy

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From the Guidelines

GLP-1 medications like semaglutide and liraglutide should not be used by underweight individuals as they pose significant health risks, including dangerous additional weight loss, malnutrition, muscle wasting, and electrolyte imbalances, as evidenced by their mechanism of action and the potential for severe side effects 1. The primary concern with using GLP-1 receptor agonists in underweight individuals is the potential for exacerbating nutritional deficiencies and promoting further weight loss, which can lead to a range of serious health complications.

  • The mechanism of GLP-1 receptor agonists, which includes reducing appetite, slowing gastric emptying, and increasing feelings of fullness, can worsen nutritional status in already thin individuals 1.
  • Underweight patients may experience more severe side effects, including nausea, vomiting, and diarrhea, which could further compromise their nutritional status and lead to dehydration and electrolyte imbalances.
  • Excessive weight loss in underweight individuals can lead to hormonal disruptions, menstrual irregularities in women, decreased bone density, immune system suppression, and cardiovascular complications, highlighting the need for caution when considering weight management strategies for this population. The use of GLP-1 receptor agonists is specifically indicated for individuals with obesity or overweight conditions, and their safety and efficacy in underweight individuals have not been established, making it essential to prioritize alternative approaches to weight management that focus on healthy nutrition and lifestyle habits rather than medication 1.

From the Research

Dangers of GLP-1 in Underweight Individuals

  • There are no research papers to assist in answering this question as the provided studies focus on the efficacy and safety of GLP-1 receptor agonists, such as liraglutide and semaglutide, in individuals with obesity or overweight, rather than underweight individuals 2, 3, 4, 5, 6.
  • The studies suggest that GLP-1 receptor agonists can be effective in promoting weight loss in individuals with obesity or overweight, but do not provide information on the potential dangers of using these medications in underweight individuals.
  • It is important to note that the use of GLP-1 receptor agonists in underweight individuals may be associated with potential risks, such as excessive weight loss or malnutrition, but further research is needed to fully understand these risks.

Efficacy and Safety of GLP-1 Receptor Agonists

  • The provided studies demonstrate the efficacy and safety of GLP-1 receptor agonists, such as liraglutide and semaglutide, in promoting weight loss in individuals with obesity or overweight 3, 4, 5, 6.
  • Semaglutide has been shown to be more effective than liraglutide in promoting weight loss, with a greater percentage of participants achieving a weight loss of 10% or more 4.
  • However, semaglutide has also been associated with a higher incidence of adverse events, such as gastrointestinal symptoms and hypoglycemia 5.

Comparison of Liraglutide and Semaglutide

  • The studies compare the efficacy and safety of liraglutide and semaglutide in promoting weight loss in individuals with obesity or overweight 4, 5, 6.
  • Semaglutide has been shown to be more effective than liraglutide in promoting weight loss, but may be associated with a higher incidence of adverse events 4, 5.
  • Liraglutide may be a safer alternative to semaglutide, but may be less effective in promoting weight loss 6.

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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