Private clients and clinic patients have come to me with this one more times than I can count.

“My friend said keto wrecked her thyroid.” “My doctor told me carnivore would shut down my metabolism.” “I saw a video that said low-carb diets destroy thyroid function.” The phrasing changes; the fear doesn’t.

I get why it’s scary. Your thyroid affects everything—energy, mood, weight, temperature regulation, hair, skin, digestion. When someone tells you that the way you’re eating could damage the gland that controls all of that, it’s going to get your attention. It should get your attention; that’s not a small claim.

Here’s the thing, though: in my experience, the claim doesn’t hold up the way it’s presented. Not because thyroid panels are never off in people eating low-carb—sometimes they are—but because the diet itself is almost never the isolated cause. There’s a lot more going on than what ends up in the headline.

What I Actually See in Practice

When a thyroid panel comes back looking off in someone eating keto or carnivore, there are typically too many compounding factors to accurately pin it on the diet alone. What I’ve found is that it’s usually a combination of things working against the person—and many of them have nothing to do with what’s on the plate.

Stress is one of the biggest ones. Chronic psychological stress, work stress, relationship stress—all of it affects the hypothalamic-pituitary-thyroid axis. Your body doesn’t distinguish between types of stress very well; it just knows it’s under siege. I dig into the self-reinforcing stress loop and how to start unwinding it in a separate post.

Environmental stressors and exposures play a role that I think is wildly underappreciated. We’re swimming in endocrine disruptors—in our water, our cleaning products, our personal care products, our cookware. Some of these directly interfere with thyroid function, and most people aren’t even thinking about them when they get their labs done.

Under-eating is a huge one, especially in women. People start a low-carb diet and accidentally slash their caloric intake dramatically. Your thyroid will absolutely respond to that by downregulating—not because of the carbohydrate restriction, but because the body is sensing a famine.

Incorrect fat-to-protein ratios during the wrong phases come up a lot. Someone who needs to go through a healing phase might be eating like they’re in a weight loss phase, or vice versa. The macronutrient ratios that support thyroid function in someone who’s actively trying to lose weight are different from someone who needs to let their body recover and stabilize.

OMAD at the wrong time—particularly for women. One meal a day can be a powerful tool in the right context, but it can also be a stress signal to the body when the timing isn’t right. I’ve seen thyroid-related symptoms improve significantly when women move from OMAD to two or three meals a day.

The Male-Female Distinction

This is something I don’t think gets enough attention: women are more affected by any of these factors being out of alignment than men are. It goes back to how we’ve lived for the majority of our existence as humans—female physiology is more sensitive to signals of scarcity, stress, and environmental disruption. That sensitivity isn’t a flaw; it’s a feature of a system that evolved to protect reproductive function and long-term survival. It just means the margin for error is smaller.

If you read the Women Warriors post I wrote recently, this connects directly. Female immune vigilance, hormonal complexity, and decades of self-sacrifice create a narrower window where everything needs to be working together. When it’s not, the thyroid is often one of the first things to show it. The menopausal transition is another place where this same narrow window shows up—the same factors that destabilize thyroid function are often the ones making perimenopause harder than it has to be.

The Iodine Factor

Iodine is another piece that gets overlooked in these conversations. It plays a major role in thyroid function, and a lot of people aren’t getting enough of it—especially if they’ve cut out iodized salt or aren’t eating seafood regularly.

What I’ve seen is that appropriate iodine supplementation tends to improve thyroid-related symptoms. Not in every case, and not as a magic bullet, but as one piece of a larger picture. Getting out of an environment that steals our iodine supplies—whether that’s through halide exposure (fluoride, bromide, chlorine) or just dietary insufficiency—helps.

The Critical Thinking Gap

Here’s what frustrates me about this conversation: there’s not enough critical thinking and awareness of all the different factors that play into thyroid health. People don’t seem to do their due diligence when it comes to sorting through stress, environmental exposures, caloric intake, meal timing, nutrient status, and hormonal context before making a determination about what caused the problem.

It’s easier to point at the diet. The diet is visible, it’s different from what most people eat, and it makes for a compelling narrative. “I went keto and my thyroid tanked” is a cleaner story than “I went keto while chronically stressed, under-eating, exposed to environmental toxins, deficient in iodine, and doing OMAD during a phase where my body needed more nourishment.”

I’ll be direct: it seems like it has become the hip and cool thing to blame low-carb diets, keto, and carnivore for thyroid problems. The narrative has taken on a life of its own, and it’s spreading faster than the nuance can keep up.

What the Evidence Actually Shows

Dr. Eric Westman—Associate Professor of Medicine at Duke University, Director of the Duke Keto Medicine Clinic, and someone whose work I’ve followed closely—has addressed this directly. His clinical experience across thousands of patients on low-carb and ketogenic protocols doesn’t support the idea that carbohydrate restriction inherently damages thyroid function. What it supports is what I see in my own practice: when the thyroid is struggling, the answer is almost always in the details that nobody’s looking at.

The research on this is consistent with that clinical picture. T3 levels may shift on a low-carb diet—that part is real. What gets lost is the context: a lower T3 in someone who’s eating low-carb and metabolically healthy may not mean the same thing as a lower T3 in someone who’s metabolically struggling. The body adapts. Efficiency changes. Reading the number without reading the person is where the interpretation falls apart—a principle I dig into more specifically in Your Labs Are a Snapshot—Not a Verdict.

What Actually Helps

When I work with someone whose thyroid markers are off while eating low-carb, here’s what I look at—and what I’ve seen actually move the needle:

  • Stress reduction and management—this improves symptoms more consistently than almost anything else
  • Removing environmental stressors—endocrine disruptors in personal care products, cookware, and water
  • Getting in enough food—real, adequate calories, especially for women
  • Stopping OMAD and moving to two or three meals a day when the timing isn’t right
  • Iodine status—assessing and addressing deficiency when it’s there
  • Making sure macronutrient ratios match the phase the person is in—healing, maintenance, or active weight loss

None of that requires abandoning a low-carb approach. It requires fine-tuning it; it requires understanding the person in front of you; and it requires not accepting a simple narrative when the reality is more complex.

The Bigger Point

I don’t think keto or carnivore diets are above criticism. Nothing is. What I do think is that the criticism needs to be honest, thorough, and grounded in the full clinical picture—not in a headline that gets engagement because it scares people.

If your thyroid is struggling, that’s worth investigating. Deeply. With someone who’s going to look at all the factors, not just the one that’s easiest to blame. The diet might need adjusting—maybe even significantly. What I don’t believe, based on everything I’ve seen in practice so far, is that therapeutic carbohydrate restriction inherently destroys thyroid function. The story is more complicated than that; it always is.

Time will tell as more research comes out. In the meantime, I’ll keep watching the labs, listening to the people in front of me, and adjusting based on what the evidence and the experience actually show.

I hope these clinical observations give someone some hope and direction.

Photo by Polina Tankilevitch on Pexels

Rance Edwards is a National Board Certified Health and Wellness Coach (NBC-HWC) with over 2,000 clinical hours of experience, specializing in chronic disease management and lifestyle medicine.

Worried about how your diet might be affecting your thyroid—or dealing with symptoms that don’t seem to have a clear answer? I’d love to help you sort through the noise. Book a free discovery call—no pressure, just a conversation about where you are and what might be going on.