Think an underactive thyroid is to blame for your weight gain? Read on.

By Jaime Milan
April 04, 2019
JGI/Jamie Grill/Getty Images

The thyroid is a small, butterfly-shaped gland in the front of your neck which makes two types of hormones that control how the body uses energy—including how fast you burn calories and how quickly your heart beats. It also helps major organs function properly.

An overactive thyroid (also called hyperthyroidism) can lead to feeling restless and/or unintentionally losing weight, while an underactive thyroid (also called hypothyroidism) can lead to feeling sluggish and/or unintentionally gaining weight.

If you’re struggling with weight loss, it's possible that an underactive thyroid may be to blame. Here’s what you need to know.

How Can I Tell if I Have Hypothyroidism?

An underactive thyroid means you have a slower metabolism and burn fewer calories at rest. The first sign will probably be a feeling of constant, extreme exhaustion, but as your metabolism slows down further, different symptoms can eventually manifest. Here’s what to look out for, according to the U.S. Department of Health:

  • Feeling cold when other people do not
  • Constipation
  • Muscle weakness
  • Weight gain, even though you are not eating more food
  • Joint or muscle pain
  • Feeling sad or depressed
  • Feeling very tired
  • Pale, dry skin
  • Dry, thinning hair
  • Slow heart rate
  • Less sweating than usual
  • A puffy face
  • A hoarse voice
  • More than usual menstrual bleeding

It’s also worth noting that women are eight times more likely than men to have thyroid conditions, and up to 30 percent of people with type 1 diabetes also have a thyroid condition. But even if you don’t fit into these categories, you still might want to see a doctor if you are exhibiting any of these signs or symptoms. The American Thyroid Association has a handy tool to help you find an endocrine-thyroid specialist in your area.

Once you’re at the doctor’s office, they’ll likely ask about your family history, symptoms, and conduct a physical exam. They may also administer blood tests or a thyroid-hormone stimulation test to gauge your thyroid hormone production and rule out other diseases. If it’s determined you have hypothyroidism, your doctor may prescribe thyroid medications.

What About Weight Gain and Hypothyroidism?

Though there’s a lot of misinformation floating around the internet, there’s no “official” diet for hypothyroidism and there’s (unfortunately) no cure for the condition. However, the American Thyroid Association recommends following a healthy diet and (of course) adhering to the treatment plan prescribed by your doctor to manage it.

Your biggest question is probably: “How much weight will I lose after I take my thyroid meds?” The answer, it turns out, isn’t cut and dry. According to the American Thyroid Association, since much of the weight gain in hypothyroidism is actually due to salt and water retention, “when the hypothyroidism is treated one can expect a small (usually less than 10% of body weight) weight loss. However, since hypothyroidism usually develops over a long period of time, it is fairly common to find that there is no significant weight loss after successful treatment.”

Brierley Horton, MS, RD, adds, “Getting into a medication regimen will not make those unwanted pounds melt off. But once your metabolism is humming along, that’s when your efforts to improve your diet and up your activity should start to yield results.”

What to Eat or Avoid When You Have Hypothyroidism

Certain raw foods contain goitrogen compounds that may suppress thyroid function by interfering with iodine absorption. They include spinach, peanuts, soybeans, strawberries, sweet potatoes, peaches, pears, and cruciferous vegetables including broccoli, Brussels sprouts, cabbage, cauliflower, mustard greens, and radishes. The compound can also be found in large amounts of uncooked kale or cabbage.

Horton says, “You don’t have to avoid any of these foods, but if you eat them fairly often (and you eat them raw), you should give your doctor a heads up. My understanding is that if you’re taking medication for your thyroid, you want to be consistent in how much of these foods you eat. So, for example, if your doctor knows you have a kale salad every other day or so, that will let her or him dial in on the correct prescription dose. And keep in mind that bingeing on kale and spinach smoothies (like, say, with a green smoothie cleanse) could throw off your numbers.”

The Bottom Line

Whether you’re just getting diagnosed with a thyroid condition, or you’re frustrated because you can’t seem to lose weight, a healthy (and consistent) diet can help. Here are some tips for finding a nutrition plan that works for your lifestyle. And, as always, talk to your doctor to find out what’s best for you.

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