There is nothing quite as annoying as unintended weight gain, especially if you don’t know why it’s happening.

Weight gain can be a signal that something else is going on with your body. Many vitamin, mineral, and hormone deficiencies are linked to metabolic disorders that affect your body’s natural ability to manage weight.

Of course, it’s important to remember deficiencies alone are often not the sole cause for this. You should always rule out other possible factors, like chronic conditions, before concluding that a deficiency is the root of your weight issue.

Read more: The 10 leading reasons why you could be gaining weight

Still, if you've noticed an increase in weight that seems out of the ordinary, you may want to talk with your physician about determining if your body is experiencing any of the following issues.

An underactive thyroid gland can lead to weight gain.

Foto: The thyroid gland is responsible for managing the metabolism.sourceShutterstock

You may have heard of the thyroid - the butterfly-shaped gland that lives in the bottom part of your neck. It is part of the endocrine system in your body - aka the hormone delivery network.

According to PubMed, the thyroid gland is responsible for managing the metabolism. This regulates your body's ability to burn calories and use them for energy. It does so by producing the hormone thyroxine (also called T4) and converting it into triiodothyronine (also called T3). These hormones then travel throughout the body and tell different cells how hard they should be working. The harder they work, the more calories get burned.

Hypothyroidism is a common condition marked by an underactive thyroid gland. In hypothyroidism, the thyroid does not produce enough of those T3 and T4 hormones and that lowers the body's basal metabolic rate, or the number of calories the body actually needs to perform its basic functions at rest. Extra calories that aren't being used end up getting stored as fat.

This is why people who develop hypothyroidism notice weight gain even though they aren't eating more than usual.

Hypothyroidism is commonly caused by an autoimmune disease called Hashimoto's disease.

Your doctor may request a thyroid-stimulating hormone test to see if your T3 and T4 levels are within the normal range. If you are deficient in either, you may experience some unexpected weight gain.

Although there is no cure for hypothyroidism, there are medications that exist to manage symptoms. In the meantime, consider different approaches like an anti-inflammatory or low-carbohydrate diet to manage weight-related side effects.

An iodine deficiency can cause the thyroid to function slowly, leading to potential weight gain.

Foto: Iodine is often added to salt.sourceReuters/Thierry Roge

You may remember this element from the periodic table in your chemistry class or have heard of its liquid form, which is used as a disinfectant. It turns out our bodies also need iodine in order for the thyroid gland to produce the hormones T3 and T4. As previously stated, both hormones play a key role in determining how efficiently our bodies can burn calories.

Low levels of iodine can cause the thyroid to function sluggishly, because it cannot produce enough of these hormones. According to the American Thyroid Association, the human body cannot produce iodine on its own, which means it must be consumed as part of our diet.

If you show symptoms of hypothyroidism that are not caused by other factors like autoimmune disease, you may have an iodine deficiency.

Your physician can check for iodine deficiency with a urine sample.

A vitamin D deficiency may also contribute to unintentional weight gain.

Foto: A vitamin D deficiency can also cause joint pain.sourceShutterstock

Chances are you're familiar with vitamin D's effects on bone health. Higher levels of the vitamin can help your body support strong skeletal functions, while lower levels can lead to conditions like osteoporosis.

But research over the years has suggested that a lack of this micronutrient may also contribute to unintentional weight gain. Several studies over the past decade have found that women with vitamin D deficiencies were more predisposed to weight gain compared to women with a normal range of the nutrient.

And in May, Medical News Today cited research published by the VU University Medical Center and Leiden University Medical Center in the Netherlands that revealed higher body fat across all sexes was linked with low vitamin D levels.

Although further investigation is needed on why this occurs, Rachida Rafiq, an author of the study, told Medical News Daily that the strong association suggests a possible connection between the deficiency and the way abdominal fat is stored.

Approximately 42% of US adults have a vitamin D deficiency, which means it's fairly common. Other symptoms of the deficiency include fatigue, joint pain, and frequent infections. If you are experiencing any of these in conjunction with weight gain, you might have low vitamin D levels.

Sex hormones play a big role in managing weight.

Foto: Testosterone is used to build muscle.sourceLuc Forsyth/Getty Images

The two major sex hormones, testosterone and estrogen, have been shown to affect the body's ability to manage weight.

The hormone estrogen causes puberty in people with female sex organs and supports cardiovascular, skeletal, and nervous-system functions. It exists in three forms - estrone, estradiol, and estriol. Estradiol is known for helping the body regulate its metabolism. According to Healthline, if estrogen levels are low, there's a chance it could lead to weight gain.

Upon studying fat storage in both pre- and postmenopausal women, researchers at Concordia University discovered women who were experiencing menopause collected more fat around their abdomens than the women who were not yet menopausal. They found this change to be linked with the rapid decline in estrogen that occurs in menopause.

In premenopausal women, however, the cause for low estrogen is usually genetic. And although estrogen is commonly associated with people with female sex organs, recent research has found estrogen levels also influence metabolism in people with male sex organs.

The other sex hormone, testosterone, plays a significant role in puberty for people with male sex hormones and helps with muscle development and fat regulation. Both people with male sex organs and people with female sex organs need testosterone to build muscle.

Studies have reported that males with lower-than-normal testosterone levels have been found to have higher concentrations of body fat overall. This has a lot to do with the fact that while testosterone increases muscle development, it suppresses fat formation. When the body struggles to build muscle, energy is more likely to be stored as fat.

But before you start ordering supplements online, take caution. It is not recommended for anyone to take hormonal supplements without consulting a physician first.

There's a strong correlation between increased magnesium levels and weight loss.

Foto: Magnesium potentially influences body weight.sourceChristian Delbert/Shutterstock

In a study that examined 18,000 adults of different weights over seven years, those who were categorically obese had lower levels of magnesium in their bodies.

Magnesium is a mineral that has many jobs in the human body. One of those jobs is regulating blood glucose levels.

In order to understand how magnesium could influence body weight, one has to understand insulin resistance. Insulin is the hormone that helps transport glucose (aka sugar) from the bloodstream into organ cells. When someone is resistant to insulin their body needs to produce more of it in order for this to happen. Of course, doing this causes a person to consume more foods to acquire that glucose and, in turn, pack on extra pounds.

Reduced magnesium in the body has been linked to insulin resistance that could lead to weight gain. In a study that compared 24 nondiabetic, obese children with 24 nondiabetic, lean children, researchers found the children at higher weights consistently had lower magnesium in their body. The study also presented data that showed insulin resistance was present in children with lower magnesium.

Although this does not necessarily mean low magnesium is a direct cause of weight gain, the strong correlation between increased magnesium levels and weight loss is also worth considering.

Other signs of magnesium deficiency include muscle twitches, fatigue, asthma, high blood pressure, and an irregular heartbeat.

A serotonin deficiency might cause you to eat more than you normally would.

Foto: You also might crave carb-heavy foods.sourceAP/Brandon Wade

Serotonin is a neurotransmitter that allows the body's nerve cells to communicate with each other. It's often brought up when people discuss mental health, but serotonin is also responsible for many physical body functions. In addition to regulating our moods, serotonin influences sexual function, bowel movements, appetite, and sleep cycle.

Healthline noted that weight gain is a physical symptom of serotonin deficiency.

This may be because serotonin is responsible for signaling to your body and brain when it's satiated during a meal. When the body has lower levels of it, it can be harder for your brain to know when you're actually full. This leads to potential overeating and possible weight gain.

In addition, reduced levels of serotonin are known to cause cravings for starchy and sugary foods.

Robert Lustig, a pediatric neuroendocrinologist and a professor of pediatrics at the University of California, San Francisco, wrote an article for The Atlantic that noted how high carbohydrate foods facilitate tryptophan movement. Tryptophan is the amino acid that helps both the brain and body make the serotonin chemical. As a result, a person will crave more of these foods to compensate for lower levels of serotonin it in the body.

Of course, if a person eats a large quantity of high-carb and high-sugar foods, it's likely they'll pack on extra weight.

Over the past two decades, scientists have discovered that artificially increasing serotonin often leads to better control in appetite. However, medications that have been used to stimulate weight loss by increasing serotonin levels have sparked controversy because of their potentially harmful side effects, according to Science Daily.

And given that there isn't really an easy test to measure serotonin levels, it's best for you to discuss other symptoms you may have with your physician before beginning any treatment. However, if you suspect you have a serotonin deficiency causing weight gain, you can try natural remedies, like exercise, to combat it.

A lack of sleep can lead to weight gain.

Foto: Less sleep leads to an increased appetite.sourceDavid Prado Perucha/Shutterstock

Sleep deficiency is caused by several factors, including poor sleep quality and sleep deprivation, both of which can lead to weight gain.

Katherine Zeratsky, a registered dietitian and an editor at the Mayo Clinic, stated that research suggests less sleep leads to increased appetite. This could be one reason why people who are sleep-deprived can experience an unexpected rise in body weight.

"One explanation might be that sleep duration affects hormones regulating hunger - ghrelin and leptin," Zeratsky said. "Another contributing factor might be that lack of sleep leads to fatigue and results in less physical activity."

The American Journal of Epidemiology published a study in 2006 that suggested a connection between reduced sleep and weight gain in women.

The study said: "Hypothalamic-pituitary functions, including those that influence eating, energy balance, and metabolism, are strongly tied to circadian rhythms and are highly integrated with sleep regulatory processes."

In other words, we need regular rest if we want our bodies to efficiently use energy, and if we want our metabolism to do its job.

Similarly, conditions like obstructive sleep apnea also contribute to sleep-deficiency-related weight gain. In obstructive sleep apnea, the flow of oxygen is interrupted, causing the body to not breathe correctly during sleep. This means the body and all of its organs aren't really resting as well as they should.

Regardless of the number of hours asleep, someone with sleep apnea who isn't getting quality rest is unlikely to feel rested during the day. This suggests that when the body doesn't recharge, functions like the ability to burn fat will be affected.

Read more: 17 things you need to know about your thyroid - because it controls a lot more in your body than you'd think

If you suspect you have sleep apnea or another sleep-related condition that could be affecting your weight, consider talking to your physician about a sleep study.

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