The Role of Fiber in Weight Loss for Thyroid Patients

Getting enough fiber in your diet is one of the essential tactics that most thyroid patients need to follow as part of a successful weight loss program.

Bowls of salad on a table
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Health Benefits of Fiber

Fiber has so many benefits for everyone, but especially for people with an underactive thyroid—hypothyroidism—who are trying to lose weight.

  • Fiber helps with constipation. People with hypothyroidism often have slowed digestion, and chronic constipation is a common complaint, even when an underactive thyroid is being treated. Getting sufficient levels of fiber can help promote regularity in bowel movements, and relieve chronic constipation.
  • Fiber can minimize blood sugar swings. Higher-fiber foods are digested more slowly, and their sugars are also released more slowly. This means that these foods have a lower "glycemic index." Choosing higher-fiber foods can, then, help blunt more dramatic swings in blood sugar, and the resulting decrease in normal insulin response (insulin resistance) that can develop. Difficulty properly metabolizing carbohydrates and handling glucose appear to be more common in thyroid patients, who also face a higher risk of insulin resistance.
  • Fiber can help lower the glycemic load of foods. Apart from choosing high-fiber foods, you can also take fiber supplements along with higher-glycemic foods, and in a sense, "transform" a high-glycemic food into a lower-glycemic food. For example, if you HAVE to have that sugary dessert or bowl of pasta—both high in sugar and high on the glycemic index—some experts recommend taking several tasteless capsules of psyllium with your food. Psyllium is an excellent source of fiber, and when taken along with high-glycemic foods, it can help slow the digestion and minimize the glucose spikes that are typical after a high-carbohydrate treat or meal.
  • Fiber can help lower cholesterol. A high-fiber diet can help lower unhealthy cholesterol levels. Elevated cholesterol can be a symptom of untreated hypothyroidism, and is also more common even in those being treated for an underactive thyroid.
  • Fiber can help you lose weight. High-fiber foods take longer to digest, and fills you up more quickly.

As I wrote in my book, The Thyroid Diet Revolution:

One study found that adding 14 grams per day of fiber was associated with a 10% decrease in energy intake and weight loss of 5 pounds over 4 months. In another study, a group of 53 women who were moderately overweight followed a 1,200 calorie a day diet, over 24 weeks, with half given a fiber supplement, and the other half receiving a placebo. After treatment, the fiber group lost a mean amount of 17.6 pounds, versus 12.76 pounds in the placebo group.

How Much Fiber

Men up to 50 typically require 30 to 40 grams of fiber a day, and women need around 25 to 30 grams. The typical American diet, however, includes around 10 grams a day or less of fiber.

Getting Enough Fiber

You will want to incorporate as many fiber-rich foods as you can. Our weight loss expert Malia Frey has an excellent list of high-fiber foods. But keep in mind, many thyroid patients are sensitive to grains, and in particular wheat: as a result, high-fiber grains, breads, and pastas may deliver fiber, but can also derail weight loss efforts. When using fiber to aid in weight loss, you will want to focus on the highest-fiber vegetables, legumes, beans, nuts, seeds, and to a lesser extent, fruits.

You have to eat a great deal of food in order to get to targeted fiber levels. To get to the optimal intake of fiber a day, you will probably have to add a fiber supplement, in addition to emphasizing fiber-rich foods in your diet.

Start slow, and don't go from “10 to 30” in one day—you need to give your intestinal system time to adjust, since adding too much fiber too quickly can cause discomfort.

Fiber Supplements

There are a number of different fiber supplements available. My favorites include:

  • Psyllium. One study found that women who took 20 grams of psyllium before a meal ate less fat, and felt full more quickly during that meal, helping with weight loss. Psyllium husk is found in commercial products like Metamucil. You can also get psyllium powder or—my preferred form—psyllium capsules. Psyllium is inexpensive, and when taken in capsules, it's easily portable and easy to take—no drinking of gloppy, sludgy fiber powder in water.
  • Guar Gum – Guar gum is a high-fiber supplement. It's found in a popular fiber product, Benefiber, which comes as a powder. Unlike some other fibers, including psyllium, guar gum dissolves completely into drinks (like juice, water or smoothies), with no grit or bulk. You can easily add it to juice or water, and it has no taste—you won't even know it's there.

Important Warning

If you switch from a low-fiber to high-fiber diet, be very careful that you are taking your thyroid medicine at least an hour before eating or drinking coffee in the morning, so your absorption is not impaired. High-fiber diets can significantly change your thyroid drug dosage requirements, so 6 to 8 weeks after starting a high-fiber diet, you should have your thyroid function tested to make sure you don't need a dosage change.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. UCSF Benioff Children's Hospital. Why fiber is so good for you.

  2. NIH MedlinePlus. Hypothyroidism.

  3. Hage M, Zantout MS, Azar ST. Thyroid disorders and diabetes mellitus. J Thyroid Res. 2011:439463. doi:10.4061/2011/439463

  4. Harvard Health Publishing. Psyllium fiber: Regularity and healthier lipid levels?

  5. Harvard Health Publishing. Fiber-full eating for better health and lower cholesterol.

  6. Mary Shomon. The thyroid diet revolution.

  7. UCSF Health. Increasing fiber intake.

  8. The role of fiber in weight loss with hypothyroidism unique high-fiber supplement helps with fiber intake.

  9. NIH National Institute of Diabetes and Digestive and Kidney Diseases. Thyroid tests.

By Mary Shomon
Mary Shomon is a writer and hormonal health and thyroid advocate. She is the author of "The Thyroid Diet Revolution."