6 Potential Causes of Unexplained Weight Gain

As a Family Medicine physician, I often encounter patients who report unexplained weight gain. This can be a frustrating and confusing experience, especially if you’re doing everything “right” to maintain a healthy lifestyle.

I will tell you about some potential causes of unexplained weight gain and provide guidance on what to do if you find yourself in this situation.

1. Hormonal Imbalances

One of the primary culprits behind unexplained weight gain is hormonal imbalances. Hormones act as chemical messengers that regulate various functions within our bodies, including metabolism, appetite, and fat storage.

Thyroid Issues

The thyroid gland plays a crucial role in controlling our metabolism. When it’s not functioning properly, it can lead to weight gain. Hypothyroidism, or an underactive thyroid, is a condition where the thyroid gland doesn’t produce enough thyroid hormones, causing a slowdown in metabolism.

This can result in weight gain, fatigue, and other symptoms. If you suspect a thyroid issue, it’s important to consult with a healthcare professional for proper diagnosis and treatment.

Polycystic Ovary Syndrome (PCOS)

PCOS is a hormonal problem that affects women of reproductive age. Specifically, it is characterized by high levels of androgens (male hormones) and insulin resistance.

These hormonal imbalances can lead to weight gain, particularly around the abdomen. If you experience symptoms like irregular periods, excessive hair growth, or acne, it’s essential to seek medical advice to determine if PCOS is the cause and receive appropriate treatment.

2. Medications

Some prescribed medications can cause weight gain as a side effect. These include certain antidepressants, antipsychotics, and medications for diabetes, epilepsy, and high blood pressure.

If you have recently started taking a new medication and have noticed unexplained weight gain, speak with your physician. They may be able to adjust your dosage or recommend an alternative treatment that may not have this side effect.

3. Sleep Deprivation

Getting enough sleep is crucial for maintaining a healthy weight. When we don’t get enough rest, our bodies produce more ghrelin (a hormone that stimulates appetite) and less leptin (a hormone that suppresses appetite).

This can lead to an increase in hunger and a decrease in the feeling of fullness, causing us to consume more calories. Get 7-8 hours of sleep per night to keep your hormones in check and reduce the risk of weight gain.

4. Stress and Emotional Eating

Stress can have a significant impact on weight gain. High levels of stress can increase cortisol levels, which can lead to increased appetite and cravings for high-calorie, sugary foods.

Emotional eating can also contribute to weight gain, as some individuals may turn to food for comfort in times of stress or emotional turmoil.

Managing Stress

To minimize the impact of stress on your weight, consider incorporating stress-reducing activities into your daily routine, such as meditation, yoga, or deep breathing exercises.

Additionally, ensure you are getting adequate sleep and engaging in regular physical activity to help keep stress levels in check.

5. Fluid Retention

Yes, fluid retention can cause sudden weight gain. When the body retains excess fluid, it can lead to rapid and noticeable weight gain over a short period of time, often within a few days.

This sudden increase in weight can be particularly noticeable in areas such as the legs, ankles, feet, hands, and abdomen.

Several factors can contribute to sudden fluid retention, including:

  1. Dietary changes: A sudden increase in salt intake can cause the body to retain more water, leading to rapid weight gain.
  2. Hormonal fluctuations: Women may experience sudden fluid retention and weight gain during their menstrual cycle due to hormonal changes.
  3. Prolonged sitting or standing: Remaining in one position for an extended period can cause fluid to accumulate in the lower extremities, resulting in sudden weight gain in the legs and ankles.
  4. Medications: Some medications, as mentioned earlier, can cause sudden fluid retention as a side effect.

If you experience sudden weight gain due to fluid retention, it’s essential to identify the underlying cause and address it accordingly. In some cases, simple lifestyle modifications like reducing salt intake, staying hydrated, and including regular exercise can help alleviate fluid retention.

6. Menstruation

Menstruation can also cause unexplained rapid weight gain in some women. Earlier, I mentioned hormonal changes during the menstrual cycle can cause the body to retain more water.

This is particularly true in the days leading up to menstruation, when levels of progesterone decrease and estrogen increases, causing the body to retain water and leading to bloating and weight gain. This weight gain is usually temporary and resolves within a few days after the period starts.

What to Do If You’re Experiencing Unexplained Weight Gain

If you’re dealing with unexplained weight gain, it’s best to consult a healthcare professional who can help determine the underlying cause and recommend the appropriate treatment.

In the meantime, focus on maintaining a balanced diet, getting regular exercise, and prioritizing self-care to support your overall health and well-being. Remember, every individual is unique, and it’s crucial to be patient and persistent in finding the right solution for you.


Unexplained weight gain can be caused by various factors, including hormonal imbalances, certain medications, lack of sleep, stress, and underlying health conditions like hypothyroidism and polycystic ovary syndrome (PCOS).

Nevertheless, it’s crucial to speak with a healthcare professional if you’re experiencing unexplained weight gain to rule out any potential underlying health issues.

Also read: 10 Tips to Fasten Your Weight Loss

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