Does Metformin Cause Weight Loss?

metformin and weight loss

If you struggle with weight gain, you’re not alone. In the United States, more than 73% of adults over the age of 20 are in the overweight or obese range, based on BMI measurements. But losing a healthy amount of weight (as agreed with your healthcare provider) and keeping it off can be a challenge for many people – and you may be curious about medications like metformin to help you on your weight loss journey. Although metformin is not designed as a weight loss drug, research suggests that it may help people lose unwanted weight. 

What is Metformin?

metformin and weight loss

Metformin is a medication used to treat type 2 diabetes (T2D). Metformin helps lower blood sugar levels in people who cannot reach their goals with diet and exercise alone. The American Diabetes Association (ADA) considers it the first-line diabetes medication of choice for people 10 years of age and older with diabetes.

The primary purpose of metformin is to lower blood sugar levels. It does this in three ways. First, it reduces the production of glucose in the liver. Second, it slows the absorption of glucose through the intestines. Third, it increases insulin sensitivity, which helps the body process glucose better.

Metformin may be prescribed off-label for several other purposes. These include gestational diabetes (diabetes diagnosed during pregnancy), type 2 diabetes prevention, and polycystic ovary syndrome (PCOS). Medical professionals also prescribe medications for people taking antipsychotic medications to control the weight gain associated with these medications.

How Metformin Works

Metformin starts working in your gut. Some scientists believe it changes the balance of natural bacteria in your digestive system. It also turns on specific enzymes that help your body use fat more efficiently.

Scientists have also been trying to understand how metformin causes weight loss. Because it alters intestinal bacteria, digestive problems are a common side effect. So one early theory was that stomach pains caused people to lose their appetite and eat less, or that they lost water weight because of diarrhea. However, most of these side effects go away after a few weeks. People who lose weight with metformin continue to lose weight after this time.

A more likely explanation is that the changes in the gut from metformin suppress appetite. It may raise the body’s leptin levels, making you feel full. Since your appetite is not working overtime, you eat less.

With this medication, your weight comes mainly from fat stores, rather than the mix of fat and lean muscle that happens when you diet. People taking metformin also had a decrease in waist circumference and waist-to-hip ratio, which are two measures of body fat.

Does Metformin Help With Weight Loss?

Research does not have a definitive answer as to why metformin causes weight loss.

This is likely due to several different effects of the drug:

  • Reduced hunger: Metformin plays a role in hunger cues. The study noted that people who took metformin had lower levels of hunger. The drug does not suppress appetite, but changes the part of the brain that regulates appetite. Metformin may cause people to eat less at each meal, which may help them lose weight.
  • Side effects of the drug: Metformin may cause nausea and diarrhea. Initially, while a person is adjusting to the drug, the combination of upset stomach, eating less and diarrhea may lead to temporary weight loss. 
  • Better insulin and glucose balance: Because metformin increases sensitivity to insulin and reduces the amount of glucose circulating in the blood, it may reduce the amount of excess glucose stored as fat. Over time, this may lead to weight loss.
  • Gut health: Studies have shown that people living with obesity may have fewer short-chain fatty acids in their intestines. These acids are protective of many aspects of health, including body weight. Metformin increases the production of short-chain fatty acids, which may contribute to weight loss.

Some studies have shown that metformin does not affect body weight, except for dietary and lifestyle changes that people taking metformin may make.

Other studies have found significant weight loss in obese individuals unrelated to lifestyle factors. Several studies have reported that metformin paired with a low-calorie diet reduces visceral body fat.

Who can take Metformin?

In addition to people with type 2 diabetes, as stated, others may benefit from metformin. Some people taking antipsychotic medications may experience a condition called metabolic syndrome. Weight gain and elevated blood lipids (triglycerides and cholesterol) are among the many manifestations of this syndrome. In one study, people taking antipsychotics gained an average of 8 pounds during the first 12 weeks of treatment. For those new to antipsychotics, those taking metformin saw significantly less weight gain, lower body mass index (BMI), and lower insulin resistance.

Precaution and Risks

Metformin has a black box warning, which is the most stringent FDA label. In rare cases, metformin can cause lactic acidosis.

This occurs when metformin accumulates in the body in excess. Lactic acidosis is a medical emergency that can be potentially fatal if left untreated.

Symptoms include flushing (sudden redness), a feeling of warmth in the skin, dizziness, nausea, vomiting, changes in heart rate, and muscle pain.

Metformin may also cause unsafe complications or interactions with the following health conditions:

  • Kidney problems or disorders
  • Metabolic acidosis
  • Heart failure
  • Before surgical procedures
  • Before radiology procedures with iodine contrast

The Bottom Line on Metformin and Weight Loss

In summary, metformin can cause a modest reduction in body weight in some people with or without diabetes. Nonetheless, scientists are still studying why the drug has this effect. Many factors – including decreased appetite due to side effects of the drug – may be at play.

Ultimately, metformin is not a silver bullet. The most important thing you can do, whether to control type 2 diabetes or for other purposes, is to change your diet and lifestyle. Think of metformin as a sidekick to these steps.

Remember, too, that the FDA currently approves metformin only for use in certain people with type 2 diabetes and the people listed above, not for those who do not have this health condition. If you are taking this medication to lower blood sugar in people with diabetes, remember that metformin can have side effects that you will want to discuss and manage with your healthcare team.

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