26 Times You Should Say 'No Thanks' to the Keto Diet

23. If You Have a Diagnosed Thyroid Condition

The thyroid gland is a master regulator of metabolism, and its function can be sensitive to dietary changes. While research is still evolving, drastic carbohydrate restriction on a ketogenic diet can sometimes impact the conversion of thyroid hormones (specifically T4 to the active T3), potentially slowing metabolism further or worsening symptoms in individuals with conditions like hypothyroidism. Any significant dietary overhaul, especially one as impactful as keto, should be thoroughly discussed with an endocrinologist to ensure it won't negatively interact with your thyroid health or medication.

24. If You Struggle with Chronic Insomnia or Sleep Disturbances

While some people report improved sleep on keto, for others, particularly during the initial adaptation, it can worsen sleep quality. The extreme reduction in carbohydrates can impact the production of neurotransmitters like serotonin, which plays a role in sleep regulation (tryptophan conversion to serotonin benefits from carbohydrate presence). If you're already battling persistent insomnia, restless sleep, or waking frequently, introducing the metabolic shifts of keto could further disrupt your sleep architecture, leading to increased daytime fatigue and irritability, counteracting potential benefits.