Iron Levels May Play a Role in Weight Gain — Here’s How

Have you ever wondered if your iron levels could be affecting your weight? Iron deficiency may affect up to 1 in 3 adults, and it seems to be more common in people with a higher weight. So could iron deficiency be one of the causes of weight gain? 

Iron plays a major role in your body’s health, from keeping your energy levels up to helping your metabolism work smoothly. Iron is also a building block of red blood cells. So low iron can eventually lead to low red blood cell counts, a health condition called anemia.

Researchers are uncovering a complicated relationship between iron levels and weight. So, here, we’ll walk you through the connection between iron deficiency and weight, and anemia and weight. And we’ll go over whether treatment for these conditions can help with weight loss.

Does iron deficiency cause weight gain?

Researchers have become increasingly interested in the connection between iron deficiency and weight. Many studies have shown that iron deficiency is more common in people diagnosed with obesity. But does iron deficiency cause weight gain? Or does weight gain cause iron deficiency?

Based on the current research, it appears more likely that weight gain can lower iron levels rather than the other way around. It’s likely related to the way body fat increases inflammation in the body. And this inflammation may make it harder for the body to store iron. 

But this question is still open for debate. And some research suggests that the relationship goes both ways. In other words, there’s evidence that weight gain can lead to iron deficiency. And iron deficiency can lead to weight gain. So the take-home message is that we still don’t know.

Even if iron deficiency doesn’t directly cause weight gain, it may contribute to it in certain ways. This is because iron deficiency can lead to:

• Low energy: Low iron can cause fatigue even before it starts to affect your red blood cell count. This may affect your physical activity or ability to get regular exercise.

• Slower metabolism: Iron plays a role in a process called thermogenesis, which is how your body burns calories to produce heat. So, when iron runs low, your metabolism can slow down and make it more difficult to burn calories. 

• Changes in hormones: Iron deficiency can lead to lower levels of thyroid hormone. And one of the symptoms of an underactive thyroid is weight gain. It may also affect a hormone called leptin, which plays an important role in hunger and fullness.

• Restless leg syndrome: Some people with iron deficiency have symptoms of restless leg syndrome. In these cases, it may be challenging to get enough sleep. And this can lead to feelings of fatigue and less physical activity.

But the story doesn’t stop there. Many times, low iron levels can eventually lead to iron-deficiency anemia. And this condition can also have its own impact on weight. 

Will increasing your iron help you lose weight?

Treating iron deficiency may help with weight loss. 

One small study of people with iron deficiency showed that after 3 months, oral iron supplements were associated with:

• Weight loss

• Lower appetite and food cravings

• Lower body mass index (BMI), fat percentage, and waist circumference

This still doesn’t prove that increasing your iron intake will help you lose weight — especially for someone who isn’t iron deficient. After all, a recent review of the available studies found that iron intake was associated with both a higher and lower risk of obesity. So the relationship is clearly complicated.

All that being said, there are some practical steps you can take if you think increasing your iron intake may help with your weight loss goals:

• Getting more iron in your diet may help improve energy levels. This increase in energy levels may help with your daily physical activity and movement routine. 

• Vitamin C can help your body absorb iron, so make sure you’re getting the amount your body needs. 

• Certain foods and supplements can actually lower the absorption of iron. These include calcium, oxalates, tea, and coffee. So it may help to spread these out with your iron-rich foods or supplements.

The only way to know for sure if your iron levels are low are to get tested. So if you are concerned you could be iron deficient, talk with your primary care provider. More on this next.

What are the symptoms of iron deficiency?

Not everyone with iron deficiency has symptoms right away. And if they do, they can sometimes be hard to spot. Symptoms of iron deficiency without anemia include:

• Fatigue

• Too little energy for exercise

• Restless leg syndrome

• Hair loss

• Cravings for ice, also known as a form of pica

• Headaches

• Trouble concentrating

Symptoms of iron-deficiency anemia may include:

• Having pale skin

• Feeling extremely weak and fatigued

• Rapid heartbeat

• Pounding in the ears

• Shortness of breath, chest pain, or headache, especially with activity

• Desire or urge to eat ice or clay

• Sore tongue

• Nails that break easily

• Hair loss

If you think you may have symptoms of iron deficiency, talk with your primary care provider. Ask them to test your ferritin level.  

Ferritin is the protein in your body that stores iron. It’s an indirect way to measure the iron stores in your body. It’s also one of the first blood levels to drop when you have iron deficiency. This means that your iron levels and blood counts may look normal even though you are iron deficient. This is why your primary care provider should look at both — ferritin and iron tests — to assess your overall iron stores.  

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Written by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

Reviewed by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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