Can Metformin Help with Weight Loss?

Metformin is a prescription medication used to treat high blood sugar in patients with type 2 diabetes. However, its possible use for weight loss in those without diabetes has sparked interest among patients who would like to use it off-label.

Key takeaways:
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    Metformin is FDA-approved to treat type 2 diabetes.
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    Metformin's ability to lower blood sugar and glucose levels may stimulate the body to burn more fat.
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    Side effects have included modest weight loss in some patients, partly due to a reduced appetite.
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    Weight loss was long-term as long as participants stayed on the drug, but it is not yet approved for this purpose alone.

This article will discuss metformin's weight loss benefits, its side effects, safety information, and who should not use it for weight loss purposes.

What is Metformin?

Metformin is an antidiabetic agent approved by the FDA to treat type 2 diabetes. It is available in extended-release and immediate-release formulas. It goes by the brand names Glucophage, Riomet, Glumetza, Glucophage XR, and Fortamet.

Metformin is also used as an off-label drug for the treatment of conditions, such as:

Researchers are currently investigating the possible role of metformin's neuroprotective benefits and its possible use in anti-aging and cancer treatment. More quality, large-scale trials are needed.

How does Metformin work?

Metformin is a biguanide drug and antihyperglycemic agent. It lowers both basal and postprandial blood glucose levels. The drug also reduces the absorption of glucose in the intestine. It improves insulin utilization by stimulating the 5'-AMP-activated protein kinase and modulating lipid metabolism.

We don't know precisely how metformin works. But recent research suggests that the drug can alter the energy metabolism of the cell and influence tumorigenesis by reducing insulin levels and inducing energetic stress.

In diabetes studies, metformin use resulted in modest weight loss for some participants, but its effects on metabolism are not entirely clear. New evidence suggests that metformin weight loss could be attributed to hypothalamic appetite-regulatory centers or alteration in the gut microbiome. However, not all studies have shown statistically significant weight loss with metformin compared to a placebo.

Can Metformin cause weight loss?

The FDA has not approved metformin as a weight loss drug. Still, some researchers are investigating its potential to help people lose weight. So far, weight loss appears modest and not uniform across all participants. However, it at least does not appear to cause weight gain, and studies on rats have shown it may be able to reduce visceral (belly) fat.

A closer look at metformin's weight loss results reveals that only modest weight loss (up to 5% of body fat) occurs in some patients (less than 30%). However, those patients did experience long-term weight loss as long as they continued to take the medication. Metformin's effects on weight may be due to some or all of the effects that we discuss below.

1. Reduced appetite

Small studies have shown that metformin's effect on weight loss may be due to its ability to suppress appetite. As patients consume fewer calories, they lose weight. However, more extensive and recent studies have shown that patients lose an average of just 5 pounds over 4 years due to decreased calorie intake.

2. Blood sugar control

Our bodies only burn fat when insulin levels are low. High insulin levels can interfere with weight loss. As a result, metformin's ability to lower blood sugar also lowers insulin levels and signals to the body that it's time to burn fat, resulting in weight loss.

3. Improved gut health

Metformin may cause weight loss by altering gut bacteria to improve glucose homeostasis. While its role in the microbiome is not fully understood, any role metformin plays in glucose regulation could result in weight loss in obese type 2 diabetic patients taking the drug.

4. Drug side effects

While not a desired effect or sustainable weight loss method, it may be the case that side effects like nausea and diarrhea result in temporary weight loss. However, this is not fat loss; side effects subside when the patient becomes used to the medication.

What dosage of metformin causes weight loss?

Metformin comes in tablet form and oral release suspension. Starter doses for tablets average around 500 milligrams taken once or twice daily with meals. Standard metformin doses tend not to exceed 2500 milligrams for type 2 diabetes patients who also lose weight on metformin. When taken as an oral suspension, starter doses are 5 milliliters once or twice a day, usually not exceeding 25 milliliters.

Metformin doses differ when using the drug for different conditions. The metformin dose for PCOS is typically between 1500 and 2500 milligrams per day (with 500 mg doses taken with meals throughout the day).

Whether taking metformin for a medical condition or weight loss, it's best to take it with a meal. Taking metformin at night for weight loss helps reduce blood sugar levels after your last meal of the day and while you sleep. While it can prevent blood sugar problems in the morning, it may also cause sleep disturbances.

Higher doses of metformin are associated with more significant weight loss. In one small study, women with type 2 diabetes who have been prescribed 1700 mg three times a day experienced more weight loss than those at lower doses.

Does Metformin help to lose weight for people with conditions?

Metformin is most commonly prescribed for weight loss in people with type 2 diabetes or PCOS. Because weight loss results are modest, metformin is rarely prescribed alone as a weight loss drug.

However, in a 2013 study on non-diabetic people with obesity, the average weight loss with a dosage of 2,500 mg a day metformin was 15 pounds over six months. Patients who suffered from severe insulin resistance lost more weight, regardless of their BMI, sex, or age.

If you have a medical condition, it's important to share those details with your prescribing physician in case metformin is contraindicated.

Common side effects of Metformin

The most common side effects of metformin are:

  • Nausea;
  • Vomiting;
  • Diarrhea;
  • Stomach pain;
  • Loss of appetite;
  • A metallic taste in the mouth;
  • Flatulence.

These side effects occur in anywhere from 2 to 63% of people taking the drug. Taking an extended-release capsule can help alleviate some side effects.

When metformin is taken with other drugs, it may cause low blood sugar, which results in:

  • Feelings of hunger;
  • Trembling;
  • Sweating;
  • Confusion or trouble concentrating.

Side effects can often be avoided by eating regular meals, maintaining a healthy diet, cutting back on alcohol, exercising, avoiding fasting, and taking other medications with metformin.

Rare side effects of metformin that require a doctor's attention include:

  • Fast or shallow breathing;
  • Coldness;
  • Slow heartbeat;
  • Jaundice;
  • Serious allergic reaction resulting in trouble breathing, throat swelling, or skin rashes.

The most common long-term side effect is B-12 deficiency, which can be remedied by taking metformin with supplements.

Combining metformin with other drugs for weight loss

In patients who do not respond to metformin for weight loss, trials have investigated the use of combination treatment. For example, a 2013 study of 36 patients found that women with PCOS who had previously lost less than 5% of their body weight on metformin alone. Short-term combined treatment with liraglutide and metformin experienced more significant weight loss, a decrease in waist circumference, and lowered BMI by an average of 2.4. However, this short-term trial did not measure long-term results.

With obesity being a multifactorial disease with potentially fatal outcomes (for example, when it causes cardiac issues), weight loss drug combinations are increasingly being explored in studies.

Metformin and Ozempic

Metformin and Ozempic are prescribed together for type 2 diabetes and weight loss without drug interactions. Ozempic is an injectable semaglutide used to control blood sugar levels in type 2 diabetics and is known to suppress appetite. Appetite suppression is the primary avenue for weight loss in this combination. Possible risks include disordered eating, malnutrition, and vitamin deficiencies.

Metformin and Trulicity

Metformin and Trulicity for weight loss is another possible combination currently available to those with type 2 diabetes. Trulicity is often prescribed alongside other diabetes medications, so it's wise to ensure those are also safe to take alongside metformin. Trulicity regulates blood sugar levels by increasing insulin secretion. Weight loss results typically come from appetite suppression and insulin regulation.

Metformin and Victoza

Combining metformin and Victoza (liraglutide) can lower blood sugar to control type 2 diabetes and reduce an obese person's risk of heart disease. Victoza is an injectable medication like Ozempic. Victoza and metformin for weight loss have been effective in women with PCOS, reducing weight, BMI, and waist circumference, all of which decrease a patient's risk of heart disease.

Metformin and Phentermine

Phentermine is an amphetamine that acts as an appetite suppressant. It may be used to "jump start" weight loss and is not typically prescribed long-term since it can lead to heart irregulates. Combining metformin and phentermine for weight loss requires careful dosing by a doctor who can monitor a patient's blood sugar to avoid the risk of hypoglycemia, especially in people with diabetes.

Metformin and Spironolactone

Pilot studies have shown that using metformin and spironolactone for PCOS successfully improves PCOS symptoms and insulin resistance. However, weight loss has rarely been recorded as a side effect of the combination.

What are the signs that metformin is working?

You will know if metformin is working if your blood sugar levels go down in the 4 to 5 days following treatment. Patients may experience appetite suppression right away, or it may take weeks. Since appetite suppression is a side effect of metformin, it does not occur in everyone. Some studies show it affects about 30% of users.

If metformin suppresses your appetite and leads to weight loss, it may take weeks or months to see possible results. The average weight loss on metformin in clinical studies was 5 to 7 pounds over six months.

Metformin is not a miracle drug or a wonder drug for weight loss. Those who tend to lose weight on metformin combine it with diet and exercise modifications. However, even a loss of 5% to 10% of body fat can reduce a person's risk of developing cardiovascular issues and type 2 diabetes.

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