Metformin is a widely recognized medication, primarily approved by the U.S. Food and Drug Administration (FDA) for managing type 2 diabetes. While weight loss is a known side effect of metformin, its effectiveness as a dedicated weight loss therapy remains a more complex issue. This article clarifies how metformin influences weight, compares it to other weight loss treatments, and addresses common questions surrounding its use.
What is Metformin and How Does It Work?
Metformin belongs to a class of drugs called biguanides, and its primary function is to manage blood glucose levels. It’s most commonly used to treat type 2 diabetes because it reduces the amount of glucose released by the liver. Beyond this core function, metformin’s impact on weight is being explored.
How Might Metformin Lead to Weight Loss?
The connection between metformin and weight loss isn’t fully understood, but several theories have emerged:
- Appetite Suppression: Research suggests metformin can decrease appetite by boosting levels of molecules like lac-phe, considered an “anti-hunger” molecule, and increasing the production of appetite-suppressing hormones, GLP-1 and PYY, which signal fullness.
- Improved Insulin Sensitivity: By helping insulin function more efficiently, metformin contributes to lower insulin levels, a factor linked to weight management. Better insulin sensitivity means the body uses glucose more effectively, reducing fat storage.
- Gut Microbiome Changes: Emerging research indicates that metformin may shift the balance of bacteria in the gut. These changes may lead to weight loss, reversing metabolic changes associated with aging and boosting beneficial bacteria associated with reduced inflammation and improved glucose production.
- Gastrointestinal Side Effects: The gastrointestinal side effects of metformin, such as nausea and diarrhea, can potentially curb food intake, indirectly contributing to weight loss.
Long-Term Weight Loss: What to Expect
While metformin can initially lead to weight loss, maintaining that loss over the long term can be challenging. A 15-year study revealed that roughly 28.5% of participants taking metformin experienced weight loss exceeding 5% of their body weight. However, by years six through fifteen, only 6.2% managed to sustain that level of weight loss, highlighting the complexities of long-term weight management.
Metformin Versus Other Weight Loss Medications
For individuals with diabetes, metformin often leads to a weight loss of approximately 2 to 3% of their body weight within the first year. However, other medications specifically designed for weight loss often yield more substantial results. For instance, patients taking semaglutide drugs like Ozempic and Wegovy often report losing 15% or more of their body weight, and tirzepatide (Zepbound) studies have shown weight reductions ranging from 5% to 25%.
Off-Label Use: Prescribing Metformin for Weight Loss
Doctors occasionally prescribe metformin “off-label,” meaning for a condition it wasn’t initially approved to treat. One common off-label use is managing weight gain associated with antipsychotic medication.
Who Can Take Metformin?
Metformin is FDA-approved for treating type 2 diabetes in adults and children aged 10 and older.
Key Takeaways
- Metformin is an FDA-approved medication primarily used to treat type 2 diabetes.
- Weight loss is a recognized side effect, and it’s sometimes prescribed off-label for weight management, particularly to address weight gain related to certain medications.
- While beneficial, metformin’s impact on weight is generally less significant compared to medications specifically approved for weight loss.
Frequently Asked Questions (FAQ)
- What is Metformin? Metformin is an FDA-approved medication used to treat type 2 diabetes.
- What are the potential side effects of Metformin? Besides weight loss, side effects can include gastrointestinal issues, headaches, and muscle pain.
- How much weight can people typically lose with Metformin? Individuals with diabetes taking metformin generally lose around 2 to 3% of their body weight within the first year.
- Can Metformin be used as a weight loss drug alone? Metformin is primarily approved for diabetes treatment. While sometimes prescribed off-label, it’s not typically used as a standalone weight loss solution.
Resources We Trust
Corcoran C et al. Metformin. StatPearls. August 2023.
Weight Loss Caused by Common Diabetes Drug Tied to “Anti-hunger” Molecule in Study. Stanford Medicine. March 2024.
Yerevanian A et al. Metformin: Mechanisms in Human Obesity and Weight Loss. Current Obesity Reports. January 2019.
Wang Y et al. Advances in the Mechanism of Metformin with Wide-Ranging Effects on Regulation of the Intestinal Microbiota. Frontiers in Microbiology. May 2024.
Jones LA et al. Alterations in GLP-1 and PYY Release with Aging and Body Mass in the Human Gut. Molecular and Cellular Endocrinology. December 2023.
Apolzan JW et al. Long-term Weight Loss with Metformin or Lifestyle Intervention in the Diabetes Prevention Program Outcomes Study. Annals of Internal Medicine. November 2019.
Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine. June 2022.
Understanding Unapproved Use of Approved Drugs “Off Label”. U.S. Food and Drug Administration. February 2018.
Metformin. MedlinePlus. February 2024.
Meet Our Experts
Adam Gilden, MD, MSCE
Medical Reviewer
Dr. Gilden is an associate director of the Obesity Medicine Fellowship at University of Colorado School of Medicine and associate director of the Colorado University Medicine Weight Management and Wellness Clinic in Aurora.
Valencia Higuera
Author
Valencia Higuera is a writer and digital creator from Chesapeake, Virginia.
