Can Metformin help with Weight Loss?

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Bottom Line: Yes. About 2 to 9 kg (4 to 20 pounds) according to the studies and this fits my clinical experience.

I want to give my patients the best shot possible when trying to lose weight (and keep it off). This may or may not include giving them medicines along the way. Our bodies are working against us so we must work against them (as safely as possible).

Most approved weight loss medicines work in the brain to help us control our appetites. They can be pricey (unless generic, which are approved for short-term) and their long-term effects are unknown.

There is one medicine that has been prescribed by weight loss doctors and used by bodybuilders for years despite not being approved for weight loss with a very strong safety record. That medicine is metformin. (Or as my Siri has written in the past, Matt Foreman).

How to take it: Start with 500 mg tablet with breakfast (some say start with dinner). If you tolerate it after about a week or two, try 500 mg with breakfast and dinner. After another week or two go to 1000 mg with breakfast and dinner.

Who takes it?: It is the first-line drug treatment approved for type 2 diabetes. However, it is also commonly used in PCOS (polycystic ovarian syndrome), prediabetes (and those with insulin resistance), those taking antipsychotics looking to minimize weight gain, and adolescents/adults looking to lose weight some weight loss. There are anecdotal reports of athletes and bodybuilders taking it as well.

How does it work?: Metformin helps your muscles take in sugar (increases insulin sensitivity) and slows your liver’s sugar production (decreased hepatic gluconeogenesis). The mechanism is likely a peripheral activation of AMPK (AMP-activated protein kinase) and alteration of the gut microbiome and increases in GLP-1. You can read more than you ever wanted to know about the mechanisms here and here.

Is it safe?: Yes. Metformin is one of the safest drugs you can take with a lot of data behind it. It may even be beneficial for heart health and cancer prevention. It is even commonly prescribed among anti-aging doctors.

The worst side effects are gastrointestinal issues (see notes below). A decrease in B12 levels is seen as well (malabsorption). You may want to monitor B12 levels if you have been on it for a long time and also supplement with B12 (and calcium).

If your kidneys are sluggish, you will want to ask your doctor if it is still safe to take. There is a risk of lactic acidosis when your eGFR (glomerular filtration rate) decreases to below 45 mL/min (cut dose in half) and it is NOT to be taken when eGFR goes below 30 mL/min.

Notes: Many patients get upset stomachs. This is why we start low and go up (titrate). If this happens, stick with that lower dose for a while until you tolerate it. If after a few weeks you still don’t tolerate it, try extended-release and before bedtime. Anecdotally I find that instant release does better with appetite control when taken at breakfast.

My Experience and Thoughts

Okay, I don’t want to overhype a medicine that is probably going to only give you modest results at best. However, at the very least if you have prediabetes and/or PCOS, and you want to lose weight, you should likely discuss with your doctor about taking metformin. If you have type 2 diabetes and you can tolerate it, you better be on it as well. It is cheap, safe, and likely to help you.

For my friends who want to use it for bodybuilding and anti-aging purposes, I don’t see much harm in trying it. If I can get my hands on some (I suppose I can prescribe myself some although you’re not supposed to do that), I will use it.

I have also had good success using it in teenagers who need to lose weight and don’t qualify for the more powerful weight loss medicines. The patients tell me it helps a smidge with their appetites.


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