Should You Take Metformin for Weight Loss?

Metformin is a medication used primarily to help manage prediabetes and type 2 diabetes. It is considered a first-line treatment because it is highly effective and typically has very few side effects, according to the American Diabetes Association's (ADA's) Standards of Medical Care in Diabetes 2019.

While meformin is considered a "weight neutral" medication (in that it neither promotes weight gain or weight loss), some people with diabetes do lose modest amounts of weight while taking it, according to a study published in the September 2012 issue of Obesity. This is seen as a positive side effect, because obesity is a major risk factor for prediabetes and type 2 diabetes.

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Metformin and Weight Loss

Metformin's normal job is to lower blood sugar levels in people with prediabetes and type 2 diabetes. It is unclear why this medication also induces weight loss.

However, the Obesity study mentioned above found that participants on metformin had reduced appetites, which naturally led them to consume fewer calories. The number of calories the participants consumed was also dose-dependent: The higher the metformin dosage, the fewer calories participants consumed.

In an April 2012 study, the ADA found that metformin produced weight loss in people without diabetes, too 3. The study, which was part of a multi-year Diabetes Prevention Program Outcomes Study (DPPOS), found that metformin was also effective in delaying or even preventing type 2 diabetes 346.

Further results from the DPPOS were published in May 2019 in the Annals of Internal Medicine. The researchers found that, of the participants who lost at least 5 percent of their body weight in the first year, those taking metformin lost the greatest amount of weight during years six through 15 of the overall study 346. Essentially, the participants taking metformin experienced more effective weight loss in the long run than those who were on a placebo or who were only making lifestyle changes.

Read more: Are There Any Herbal Alternatives to Metformin?

Metformin and Fat Storage

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People with prediabetes and type 2 diabetes have insulin resistance, a condition wherein their bodies can't use the hormone insulin effectively, and therefore can't properly move blood sugar into the cells for fuel. This results in high blood sugar, which triggers the body to release even more insulin — and insulin promotes fat accumulation, as described in research published by Colorado State University 7.

Metformin makes cells less insulin resistant, meaning the body doesn't need as much insulin; less insulin in the body can mean less energy stored as fat.

But while study results are promising, metformin isn't a cure-all for obesity. "It will help with insulin resistance, which may ultimately help with weight loss if there's less unused insulin floating around [in the bloodstream]," notes Elizabeth Halprin, MD, clinical director of adult diabetes at Boston's Joslin Diabetes Center. "[But on its own], metformin is not effective as a weight-loss medication."

More research is needed to better understand how metformin works to cause weight loss. What is clear is that metformin is effective in helping prevent or delay prediabetes and type 2 diabetes — and weight loss is an important part of that prevention strategy 34.

Tips

On its own, metformin is not effective as a weight-loss medication.

Here's what you need to know about taking metformin:

Metformin Side Effects

While metformin is generally well-tolerated, there can be some adverse side effects, especially when first starting the medication.

According to the ADA, the most common reactions affect the gastrointestinal tract. They include:

• Diarrhea
• Nausea
• Vomiting
• Gas
• Abdominal Pain

Long-term use of metformin is associated with vitamin B12 deficiency in some people, according to a study published in the April 2016 issue of the Journal of Clinical Endocrinology & Metabolism 6. The body needs B12 to create red blood cells; if it doesn't have enough B12, anemia may result. The ADA suggests that people taking metformin have their B12 levels measured periodically, especially if they already have anemia or peripheral neuropathy.

In very rare cases, metformin can lead to a life-threatening condition called metformin-associated lactic acidosis, or MALA 5. **According to a study published in the February 2016 issue of Metabolism, MALA occurs in fewer than 10 people out of every 100,000 each year.

** People with critical liver or kidney conditions are at a higher risk for MALA. Excessive alcohol consumption is also a risk factor.

Warnings

Always consult with your doctor before you start taking metformin or change your dosage.

Taking Metformin

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It should be noted that though the DPPOS study showed that metformin may be effective in promoting weight loss and preventing prediabetes and type 2 diabetes, it is not a substitute for a healthy diet and exercise plan.

Metformin is available in 500 mg, 850 mg and 1,000 mg tablets or as a liquid solution.

Higher doses can mean more adverse side effects; therefore, patients typically start with the lowest dose (500 mg) to reduce the risk of adverse reactions. Once the body has adjusted, the dose can be increased as needed.

To reduce the risk of side effects, take metformin with meals. If you are taking it twice a day (breakfast and supper) and still experience side effects, talk with your doctor about switching to extended-release metformin, which has fewer side effects and only needs to be taken once a day (though it is a bit more expensive).

Read more: Foods to Eat While Taking Metformin