Is Your Thyroid Making You Fat?

Is Your Thyroid Making you Fat?

“I have zero metabolism.”

“The older I get the more my metabolism slows down.”

“Regardless of how little I eat I can’t lose weight,  I know it’s my thyroid.”


An improperly functioning thyroid can cause weight instability and change your basal metabolic rate (BMR).  Hyperthyroidism can lead to weight loss, while hypothyroidism can lead to weight gain.

Overall health status, nutritional intake, body weight and total energy expenditure can impact the effectiveness of thyroid hormone secretion.

Thyroid hormones can affect your:

  • Weight
  • Body composition
  • Body mass index (BMI)

But, Don’t Be Too Quick to Blame Your Thyroid

Many who are overweight believe a malfunctioning thyroid (hypothyroidism) is the reason for their excess body fat.  However research suggests only 2-3% of the population have hypothyroidism. The American Thyroid Association  states “Hypothyroidism can cause a mild weight gain of 5-20 pounds, but does not cause obesity.” If you have gained considerable weight, seek help to determine the real cause of your weight gain, and don’t assume it is thyroid related. 

Although common perception is that hypothyroidism can cause a person to be overweight or obese, the reverse is often true: Obesity is often associated with causing hypothyroidism, possibly due to the inflammatory nature of obesity. This kind of inflammation that affects internal body systems is referred to as “chronic inflammation,” which contributes to the development of many health conditions, including type 2 diabetes, heart disease, cancer, rheumatoid arthritis, asthma, Alzheimer’s Disease, and –yes, thyroid disease.

The gold standard for diagnosing hyper and hypothyroidism is checking thyroid stimulating hormone (TSH) and free T4 levels. If you are found to have low TSH you may be treated with oral medication. It should be noted, though, research indicates normalization of thyroid hormone does NOT guarantee weight loss.

The effective functioning of your thyroid gland is impacted by several factors including your:

  • Nutritional intake
  • Weight
  • Total energy expenditure
  • Overall health status

Nutrition and Thyroid Disease

Several micronutrients are necessary to keep your thyroid gland functioning normally. Insufficient intake of the following micronutrients can lead to a poorly operating thyroid gland:

  • Copper –shell fish,  fish, nuts, seeds, whole grains, chocolate
  • Iron- Fortified breakfast cereals, oysters, white beans, beef liver, lentils, spinach, dark chocolate ,  kidney beans, canned tomatoes, potatoes
  • Iodine – iodized salt , seafood, enriched bread, cod, Greek yogurt,  enriched pasta, egg,
  • Selenium – Brazil nuts, yellowfin tuna, halibut, ham, shrimp, enriched macaroni, beef steak, turkey, cottage cheese, egg
  • Zinc- Oysters, fortified breakfast cereals, oats, pork chop, cheddar cheese, turkey breast, shrimp, lentils, Greek yogurt


Your thyroid gland serves as a vitamin D receptor site, so it’s not uncommon for individuals with thyroid dysfunction to have some level of vitamin D deficiency.  


Many products falsely claim to increase metabolism and promote weight loss. These claims are appealing to individuals who believe they have gained weight because of a poorly functioning thyroid gland.


A positive connection exists between probiotic intake and normal thyroid function. Research suggests that a flourishing gut microbiota impacts how well the thyroid gland absorbs and uses the above mentioned micronutrients. The probiotic strains Lactobacillaceae  and Bifidobacterium  are commonly studied strains, but further research is needed before conclusive evidence can be determined.


If you believe your thyroid gland is not functioning at it’s optimum level , consult with a licensed/registered dietitian to determine if you have deficiencies of the necessary micronutrients for thyroid functioning. Your dietitian can provide a specific treatment plan tailored for you. Developing a broader understanding of how your weight and metabolic dysfunction impact one another is an important step in treating thyroid dysfunction. Your dietitian can also support you with weight loss which will a have positive influence on decreasing chronic internal inflammation, thus preventing many health conditions associated with internal inflammation.