Does Metformin Cause Weight Loss? We Investigate

Does Metformin Cause Weight Loss? We Investigate

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Disclaimer: None of the information in this article constitutes medical advice, and is just the opinion of the writer(s) and published for informational purposes only. We recommend that patients follow their doctor’s guidance in regard to weight loss medication.

Metformin is a prescription medication used to treat and manage type 2 diabetes. However there is some early research suggesting that the drug may also cause weight loss in overweight and obese patients, so patients are often curious about how effective metformin is for weight loss.

In this article we’ll review clinical studies on metformin and weight loss to provide our determination on whether the drug is safe and effective for this purpose. We'll also highlight a real user review on metformin and weight loss after 1 year, and explain whether the drug is approved by the Food and Drug Administration (FDA) for weight loss.

Research on Metformin and Weight Loss

When researchers began noting weight loss as a side effect of metformin use in early clinical trials on the drug for diabetes, more research was conducted specifically on metformin and weight loss.

An extensive medical review of metformin and human obesity was published in the Current Obesity Reports journal which evaluated results from many individual clinical trials on the topic. The researchers found that metformin was effective for weight loss and also potentially for the prevention of future weight gain.

The study authors noted that in a large study called the Diabetes Prevention Study, patients taking metformin lost 4.63 pounds over the course of a three year period.

A separate meta-study published in 2018 also concluded that metformin was effective for weight loss. Patients lost an average of 4.92 pounds more on metformin than on placebo pills. Most of the studies had a duration of around 6 months to 4 years, so this is a modest reduction in weight over that time period.

A recent clinical trial was fascinating because it found metformin to be effective for weight loss even in non-diabetic patients. Over the course of 6 months, the obese patients taking metformin lost an average of 5.6% of their body weight, which equates to a weight loss of 14 pounds for a 250 pound man, while the control group only lost an average of 0.8% of their weight.

We would consider metformin to be effective for weight loss in diabetic overweight and obese patients, and potentially effective for weight loss in non-diabetic overweight and obese patients, based on the research summarized in this section. 

Is Metformin Approved by the FDA for Weight Loss?

Metformin is not currently approved by the FDA for weight loss. It is only approved for the treatment of type 2 diabetes according to the medication’s label.

For a drug to be approved by the FDA, it must demonstrate consistent statistically significant improvements across various clinical trials that are well-designed. The FDA considers metformin’s performance in weight loss trials too inconsistent for the regulatory agency to approve the drug for weight loss at this time.

Metformin may be approved as a standalone treatment for weight loss in the future, but at this time we do not recommend using the drug for weight loss alone as that would be an "off-label" use; unapproved by the FDA.

How Does Metformin Work?

Metformin primarily works by increasing insulin sensitivity, according to StatPearls, which is one of the largest free medical databases in the U.S. and is maintained by the National Library of Medicine.

Metformin is a member of a class of drugs called biguanides, which affect several biological processes: they decrease the liver’s production of glucose, decrease how much glucose is absorbed by the intestines, and decrease blood levels of glucose.

The reason metformin may be effective for weight loss is because it normalizes processes like pre-diabetes and diabetes which cause downstream weight gain in some patients. There’s a medical term called “insulin-associated weight gain” which is documented to affect diabetics. 

Because metformin directly improves insulin resistance, it may counteract insulin-associated weight gain and halt (and even reverse) weight gain. This research suggests that metformin may not be likely to be effective in patients without any blood sugar or insulin issues. The study we referenced previously which found metformin to be effective for weight loss in non-diabetic patients still included a patient population with insulin dysregulation.

Metformin Dosage for Weight Loss

The dosage of metformin found effective for weight loss depends on the age of the patient. We want to clarify here that we do not recommend taking metformin for weight loss; we are simply reporting the research outcomes from published clinical trials on the topic. This information may be useful for consumers generally, or for patients to speak with their doctor about.

A medical review of metformin for weight loss in overweight patients without diabetes found that 2,000 milligrams (mg) per day was most effective for adolescents, while 3,000 mg per day for a maximum of 6 months was most effective for adults

A separate meta-study analyzed results from 21 individual clinical trials on metformin and weight loss. The effective dose range from the studies ranged from 1,000 mg per day to 2,550 mg per day.

Metformin for Weight Loss Real User Review

A YouTube channel called "Native Roots" has a video describing the creator's progress and frustrations using metformin for weight loss after one year. The video appears unsponsored:

Pharmacist Discusses Metformin and Weight Loss

One of the most popular YouTube videos on metformin for weight loss comes from a channel called “Pharmacist Tips.” The video has nearly 200,000 views at the time of publishing this article, and breaks down medical research on whether metformin is effective and safe long-term for weight loss:

Do We Recommend Metformin for Weight Loss?

We do not recommend metformin for weight loss. As we outlined in our article on how to lose weight fast, we believe it’s unsafe to use drugs off-label (meaning to use them in a different way than they’re approved by the FDA to be used).

While some doctors may prescribe medications off-label, we would recommend avoiding those doctors. In our opinion, the FDA is likely to have reviewed more relevant research about a drug than most doctors, and the agency may have less economic bias given that doctors can be compensated directly by drug companies. We trust the approval process of the FDA more than most doctors’ judgment in regard to off-label medication use.

There are a number of research-backed weight loss treatments that are either medications or supplements, so we find it illogical to use metformin off-label for weight loss at this time.

Our Weight Loss Supplement Recommendations

There exist several over-the-counter (OTC) weight loss supplements that don't require a prescription, and which have medical research backing.

We are not suggesting that these products are as effective as metformin; just that it may be worthwhile for an overweight patient to discuss these options with their doctor given their documented efficacy and lack of significant side effects. They may also be used in addition to prescription weight loss medication.

We recommend dietary fiber as a safe and effective weight loss supplement, especially when combined with caloric restriction.

landmark medical study found that moderate caloric restriction (750 calories per day below baseline) combined with dietary fiber intake (a minimum of 20 grams per day) caused an average weight loss of 16.03 pounds over 6 months. That’s a pace of 32 pounds per year of weight loss in overweight individuals simply by adding fiber to a moderately-restricted-calorie diet.

The fiber supplement we recommend is SuperGut Fiber Mix. It contains a clean and effective formulation: a blend of three different types of unflavored dietary fiber and zero additive ingredients. It can be mixed into liquids or foods. Interested consumers can buy SuperGut fiber at this link.

We recommend using two fiber mixes per day, which provides 16 grams (g) of fiber. This is within the effective fiber dosing range associated with the greatest weight loss outcomes in the above-linked study.

Medium-chain triglyceride (MCT) oil is another dietary supplement which has been shown in clinical trials to cause weight loss.

MCT oil is quickly absorbed by the body and increases metabolic rate, which causes fat loss. A meta-study on MCT oil documented weight loss of 1.12 pounds over 10 weeks. This equates to a potential annualized weight loss of 5.84 pounds with MCT oil supplementation.

We recommend Bulletproof MCT Oil as our top MCT oil product, because it has a clean and effective formulation. The only ingredient is MCT oil derived from coconuts, and the product has no questionable additives. Interested consumers can buy Bulletproof MCT Oil at this link.

The effective dose range of MCT oil for weight loss (based on the medical review) is 1.7 g to 10 g per day. Bulletproof's MCT oil provides 14 g in one tablespoon, so around two-thirds of one tablespoon should be a maximally-effective dosage.

Stay up-to-date on our research reviews


Metformin may cause weight loss in overweight and obese patients with either blood sugar or insulin dysregulation. 

However the weight loss effect appears moderate, and we don’t recommend metformin for weight loss because the drug is not approved by the FDA to treat obesity; only to treat type 2 diabetes. There’s significantly more research backing metformin’s efficacy for diabetes than for weight loss.

We would consider weight loss a potential secondary benefit of metformin use for type 2 diabetes who are overweight or obese, but using the drug as a standalone medication for this purpose seems illogical. There are many FDA-approved weight loss drugs, as well as many OTC weight loss supplements, with clinical backing which may be better options.

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