Weight gain can be a complex issue influenced by various factors, but your thyroid is one potential contributor that can often be overlooked. Your thyroid is a butterfly-shaped gland located in the front of your neck. Understanding the relationship between a dysregulated thyroid and weight gain can help individuals manage their health more effectively.

What is Hypothyroidism?

Hypothyroidism, an underactive thyroid, occurs when the thyroid gland produces insufficient thyroid hormones. These hormones play a critical role in regulating metabolism, which affects how the body uses calories (energy) to affect weight loss or gain (1). Thyroid hormones play a role in many other functions, including regulating heart rate, body temperature, and mood (2). There are many nonspecific symptoms of hypothyroidism which may include:

• Weight gain

• Fatigue

• Depression

• Intolerance to the cold

• Constipation

• Dry skin

• Thinning hair

How Does Hypothyroidism Cause Weight Gain?

The thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3), are crucial for metabolic processes (2). When these hormones are deficient, the body's metabolism slows down, decreasing energy expenditure. This reduced metabolic rate means fewer calories are burned, contributing to weight gain even if dietary habits remain unchanged.

Mechanisms Behind Weight Gain

1. Reduced Basal Metabolic Rate (BMR): The basal metabolic rate is the energy expended at rest. Hypothyroidism can significantly lower BMR, meaning fewer calories are needed for basic bodily functions, resulting in excess calorie storage as fat (1,2).

2. Water Retention: Hypothyroidism can cause the body to retain water, increasing body weight. This is due to the accumulation of glycosaminoglycans in tissues, which hold on to excess water (3).

3. Fat Accumulation: The imbalance in thyroid hormones can alter lipid metabolism, promoting fat storage over fat breakdown. This shift can lead to an increase in adipose tissue. It’s important to remember that weight regulation is complex due to many factors. The American Thyroid Association states that hypothyroidism may contribute to more subtle weight gain of around 5-10 pounds, as opposed to more significant weight gain. (4)

Managing Weight Gain Due to Hypothyroidism

While hypothyroidism can contribute to weight gain, managing this condition effectively can mitigate its impact on body weight. Here are some strategies:

Medical Treatment

Thyroid Hormone Replacement Therapy: The primary treatment for hypothyroidism is hormone replacement therapy, typically using levothyroxine. This medication helps normalize thyroid hormone levels, thereby improving metabolism and potentially aiding in modest weight loss for some. However, studies on this are limited and show no significant changes in weight. (5)

Lifestyle Modifications

1. Balanced Diet: Focus on a nutrient-dense diet rich in vegetables, fruits, lean proteins, and whole grains. Avoid excessive consumption of processed foods and sugars.

2. Regular Exercise: Incorporate both aerobic exercises, such as walking or cycling, and strength training to boost metabolism and muscle mass.

3. Hydration: Drink plenty of water to help reduce water retention and support metabolic functions.

Monitoring and Support

1. Regular Check-Ups: Schedule regular visits with your healthcare provider to monitor thyroid hormone levels and adjust medication as needed.

2. Professional Guidance: Work with a registered dietitian or obesity medicine specialist for personalized advice and support.

Key Takeaways on Hypothyroidism and Weight Gain

Hypothyroidism can indeed cause weight gain through a variety of mechanisms, primarily by slowing down metabolism and altering lipid metabolism. However, with appropriate medical treatment and lifestyle changes, it is possible to manage weight effectively. If you suspect hypothyroidism might be affecting your weight, consult a healthcare provider to determine the best course of action.

 Take the Next Step with Mochi Health

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This post was written by our team of health writers for informational purposes only and does not constitute medical advice. Always consult your doctor or healthcare provider for personalized guidance regarding your health. Ozempic®, Wegovy®, Mounjaro®, and Zepbound® and their delivery device are registered trademarks. Mochi Health is a telehealth clinic that offers prescriptions for these products by medical necessity only as determined by a licensed health provider.

Sources

1. Mullur R, Liu YY, Brent GA. Thyroid hormone regulation of metabolism. Physiol Rev. 2014 Apr;94(2):355-82. doi: 10.1152/physrev.00030.2013. PMID: 24692351; PMCID: PMC4044302. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4044302/

2. Shahid MA, Ashraf MA, Sharma S. Physiology, Thyroid Hormone. [Updated 2023 Jun 5]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. https://www.ncbi.nlm.nih.gov/books/NBK500006/

3. Jesper Karmisholt, Stig Andersen, Peter Laurberg, Weight Loss after Therapy of Hypothyroidism Is Mainly Caused by Excretion of Excess Body Water Associated with Myxoedema, The Journal of Clinical Endocrinology & Metabolism, Volume 96, Issue 1, 1 January 2011, Pages E99–E103, https://academic.oup.com/jcem/article/96/1/E99/2833774

4. “Hypothyroidism.” American Thyroid Association, American Thyroid Association, www.thyroid.org/hypothyroidism/. 

5. Lee SY, Braverman LE, Pearce EN. Changes in body weight after treatment of primary hypothyroidism with levothyroxine. Endocr Pract. 2014 Nov;20(11):1122-8. doi: 10.4158/EP14072.OR. PMID: 24936556.