Hypothyroidism slows down your metabolism by reducing thyroid hormone production, which often causes weight gain (usually 5–10 pounds, mainly from water and salt retention) and persistent fatigue because your body produces less energy. If you are suffering from Hypothyroidism and looking to manage your weight gain, be sure to talk with our weight loss dietitian and get your customized weight plan today!
Step-by-Step Explanation
Thyroid Hormones and Metabolism
Your thyroid produces two key hormones: thyroxine (T4) and triiodothyronine (T3). These hormones regulate how quickly your body burns calories (your metabolism). With hypothyroidism, these hormone levels drop, and your metabolism slows down. This means your body uses less energy at rest, which directly contributes to weight gain and low energy.
Impact on Weight
When your metabolism slows, your body burns fewer calories, making it easier to gain weight even if you don’t increase food intake. On average, hypothyroidism may cause about 5–10 pounds of weight gain, though most of this is water and salt retention rather than fat. However, untreated or severe cases can contribute to more noticeable weight changes.
Energy Levels and Fatigue
Thyroid hormones also play a role in how your cells use oxygen to create energy. With reduced hormone levels, your cells become less efficient, leaving you feeling tired and sluggish even after sleeping well. This fatigue often makes daily tasks harder and reduces your overall stamina.
Muscle Weakness and Exercise Tolerance
Along with low energy, hypothyroidism can lead to muscle weakness and slower recovery after activity. You might notice that physical tasks feel harder than before, which discourages exercise and can add to weight changes over time.
Emotional and Cognitive Effects
Low thyroid function doesn’t only affects your body, it also impacts your mind. You may feel mentally foggy or have difficulty focusing, which adds to the sense of fatigue. This mental exhaustion, combined with physical tiredness, further reduces your motivation and energy levels.
Individual Variation
Not everyone with hypothyroidism experiences the same degree of weight gain or fatigue. Some people notice only slight changes, while others feel significantly affected. The severity depends on how low your thyroid hormone levels are and how quickly treatment begins.
What Causes Hypothyroidism?
Hypothyroidism is most often caused by Hashimoto’s thyroiditis, but it can also result from iodine deficiency, thyroid surgery, radiation therapy, certain medications, or congenital thyroid problems.
Detailed Explanation of Hypothyroidism
Hypothyroidism happens when your thyroid gland does not make enough thyroid hormones to meet your body’s needs. The most common reason is Hashimoto’s thyroiditis, an autoimmune condition where your immune system mistakenly attacks the thyroid, gradually damaging its ability to function.
In some parts of the world, iodine deficiency remains a leading cause, since iodine is necessary for making thyroid hormones. Without enough iodine, your thyroid cannot produce adequate levels of T3 and T4 hormones. On the other hand, too much iodine may also interfere with normal thyroid activity.
If you have had thyroid surgery (removal of part or all of the gland) or radiation therapy in the neck area, your thyroid may no longer produce enough hormones, leading to hypothyroidism.
Certain medications, such as lithium (used for mood disorders), amiodarone (for heart rhythm problems), and interferon-alpha (for some cancers or infections), can also slow thyroid function.
In rare cases, congenital hypothyroidism occurs when a baby is born with an underdeveloped or missing thyroid gland. This condition affects about 1 in 2,000 to 4,000 newborns and requires early treatment.
Finally, hypothyroidism can also develop if the pituitary gland or hypothalamus fails to signal the thyroid properly, though this is uncommon.
How to Stop Weight Gain With Hyperthyroidism?
Get Thyroid Hormones Under Control
The first and most important step is to bring your thyroid hormone levels back to normal. Hyperthyroidism treatment may include antithyroid medications (like methimazole), radioactive iodine therapy, or sometimes surgery. Once your thyroid stabilizes, it becomes easier to maintain a steady weight because your metabolism stops fluctuating.
Understand Why Weight Gain Happens
While hyperthyroidism usually causes weight loss due to a fast metabolism, some people gain weight, especially after treatment, because their metabolism slows down once thyroid hormones return to normal. This is not “true obesity” but often a rebound effect from the body readjusting. Typically, this can range from 5 to 15 pounds depending on your condition and treatment stage.
Eat a Balanced, Nutrient-Dense Diet
You should focus on whole foods rich in protein, fiber, and healthy fats. Protein (chicken, fish, legumes, eggs) helps preserve muscle mass, which keeps your metabolism active. Fiber from vegetables, fruits, and whole grains keeps you fuller for longer, reducing overeating. Avoid high-sugar, processed foods that can contribute to fat storage.
Watch Your Calorie Intake Without Starving
After treatment, your body burns fewer calories than before. If you keep eating the same way you did when your metabolism was high, you may gain weight. Tracking your calorie intake helps you understand your needs. For most people, a small calorie deficit (200–300 calories per day) is enough to prevent gradual weight gain without making you feel weak.
Stay Physically Active
Regular exercise is important to prevent weight gain. Aim for a mix of aerobic activities (like brisk walking, cycling, or swimming) and strength training. Strength training is particularly effective because building muscle helps you burn more calories at rest.
Manage Stress and Sleep Well
Stress increases cortisol, a hormone that promotes fat storage, especially around your belly. Practicing relaxation techniques such as yoga, deep breathing, or meditation can help. Also, getting 7–9 hours of sleep each night supports hormone balance and appetite control.
Work With Your Doctor Regularly
Because hyperthyroidism and its treatments affect each person differently, regular thyroid function tests are necessary. By staying in touch with your doctor, you can adjust medications and lifestyle changes to better control weight gain.
How Much Weight Can You Gain With Hypothyroidism?
With hypothyroidism, you can typically gain 5 to 10 pounds, mostly from water and salt retention, though in some untreated cases, the weight gain can be higher depending on how low your thyroid hormone levels are.
Explanation
When you have hypothyroidism, your thyroid gland produces fewer hormones (T3 and T4), which slows down your metabolism. A slower metabolism means your body burns fewer calories at rest, making weight gain easier even if your eating habits do not change.
The average weight gain from hypothyroidism is about 5 to 10 pounds. Most of this increase is not body fat but water and salt retention, which happens because low thyroid hormone levels affect how your body regulates fluids.