How the thyroid regulates metabolism, the effect of hypothyroidism on weight, and how to maintain healthy thyroid function

The thyroid is a small butterfly-shaped gland in the front of the neck that produces hormones T3 (triiodothyronine) and T4 (thyroxine), which regulate metabolic rate in almost every cell of the body. When the thyroid works too slowly (hypothyroidism), the entire metabolism slows down — BMR may decrease.
Hypothyroidism affects about 5–10% of the population, and it is 5–8 times more common in women than in men. Many people struggle for years with "unexplained" weight gain until it finally turns out that the culprit is the thyroid.
Persistent fatigue, cold intolerance (always cold), weight gain without a clear cause, constipation, dry skin, hair loss.
Depression / low mood, memory problems ("brain fog"), muscle weakness and pain, hoarse voice, slowed heart rate.
High TSH (> 4,5 mIU/L), low FT4 and/or FT3. However, "subclinical" hypothyroidism (TSH 2,5–4,5) can also cause weight problems.
The thyroid is sensitive to nutritional deficiencies. Key nutrients for thyroid function:
| Nutrient | Recommended Daily Allowance | Sources |
|---|---|---|
| Iodine | 150 mcg | Seaweed, iodized salt, fish, eggs |
| Selenium | 55–100 mcg | Brazil nuts (1–2 pcs/day!), tuna, sunflower seeds |
| Zinc | 8–11 mg | Oysters, beef, pumpkin seeds, chickpeas |
| Iron | 8–18 mg | Red meat, spinach, lentils, liver |
| Vitamin D | 800–2000 IU | Sun, fatty fish, supplements |
| Tyrosine | From protein | Chicken, turkey, fish, dairy products, soy |
Some foods contain goitrogens — substances that can interfere with iodine absorption in the thyroid:
Important: There is no need to completely avoid these foods. Just eat them in moderation, cooked, and separately from thyroid medication (at least a 4-hour gap).
Use a diary or app. Weekly trends are more important than daily fluctuations. Regularly measure not only weight but also circumferences.
2–3 liters per day. Water aids digestion and metabolism and reduces false hunger.
Quality sleep is essential for hormonal balance, muscle recovery, and appetite control.
Even 30 minutes of walking per day can significantly improve metabolism and mood.