Hello, everyone! This is Dr. Cho. In this article, we'll explore the potential side effects associated with low-carb high-fat diets, intermittent fasting, or other carb-restricted and low-calorie approaches. These diets are popular for weight loss and health improvement, but they can sometimes lead to unexpected issues, especially for women, such as missed periods, low thyroid function, or insomnia. We'll take a comprehensive look at these side effects, why they occur, and practical strategies to manage them. If you find this information valuable, consider sharing it with others seeking better health.
When you embark on a low-carb high-fat diet, intermittent fasting, or similar regimens to boost your health, it's not uncommon to feel worse before you feel better. In some cultures, like in Korea, this is often referred to as a "healing crisis" or "myeonghyeon reaction." However, in functional medicine and Western medical perspectives, there's no formal recognition of this concept. Instead, these experiences are typically classified as side effects or an adjustment period.
Not everyone encounters these issues, and they're not an inevitable part of the journey to better health. They only affect a subset of people, which is why we treat them as side effects. To clarify terminology: in English, "side effect" implies secondary outcomes from a treatment, often unintended but not necessarily harmful. What we're discussing here leans more toward "adverse effects"—unwanted symptoms that provide no benefit, akin to exacerbating an itch by scratching it too hard.
These reactions aren't limited to dietary changes; they can also arise from abruptly introducing new supplements. For instance, if you follow online advice to consume 4–5 grams of MSM (methylsulfonylmethane) daily, you might experience headaches or overheating. That's not a sign of healing—it's simply a side effect.
That said, these symptoms can indicate your body is adapting to the new routine. Once the adjustment phase passes, your underlying health concerns may improve, leading some to interpret it as a "healing crisis." But it's not a required step. The goal is to transition to these diets smoothly, minimizing or avoiding discomfort altogether.
Among the most frequently reported side effects is hair loss, which can be particularly frustrating when you're adopting these diets for weight loss—only to potentially gain weight or notice thinning hair instead. It may seem counterintuitive, but it's a common complaint.
Other potential issues include cognitive fog or memory problems, insomnia, night sweats, hormonal fluctuations (such as increased irritability or anger before menstruation), nerve pain, worsening skin conditions like acne or psoriasis, heart palpitations, anxiety, feelings akin to panic attacks, and even a decrease in libido. You might hear glowing testimonials from others about how intermittent fasting or low-carb diets transformed their energy and well-being, leaving you wondering why your experience differs so starkly.
So, what triggers these side effects? Multiple factors can contribute, but toxins—particularly neurotoxins—stand out as a primary cause. As your body begins to break down fat stores during these diets, toxins accumulated in fat cells are released into the bloodstream before being eliminated. This temporary surge can lead to various symptoms. Women are often more susceptible because they generally have higher body fat percentages, which can harbor greater toxin loads.
Body fat serves dual purposes: it's not just an energy reserve but also a storage site for toxins that the body can't immediately process. Common culprits include heavy metals such as mercury, lead, aluminum, and bromine. Bromine, for example, is prevalent in flour-based products like bread. Even if you've cut out bread during your diet, decades of consumption—perhaps 10, 20 years, or more—can result in significant accumulation.
Bromine interferes with iodine absorption by competing for the same cellular sites, potentially leading to thyroid dysfunction. If bromine occupies iodine's "parking spots," your body struggles to utilize iodine effectively, even if blood tests appear normal. This explains the rising prevalence of thyroid issues in modern societies, where flour-heavy diets are common.
Heavy metals also displace essential minerals like zinc and magnesium. No matter how diligently you consume vegetables or high-quality supplements, if these metals block absorption, the nutrients won't take hold—much like trying to park in an occupied space. For individuals with diabetes, this is especially problematic, as zinc, magnesium, and B vitamins are vital for symptom management. Heavy metal interference can exacerbate issues like hair loss, nerve problems, memory lapses, insomnia, irritability, nerve pain, and night sweats.
Beyond heavy metals, herbicides such as glyphosate (and its variants like monoammonium salt, potassium salt, or isopropylamine salt) pose additional risks. These not only hinder the detoxification of heavy metals but also impair the utilization of beneficial minerals, compounding the issue. Long-term exposure to even trace amounts of pesticides or heavy metals underscores the importance of switching to organic foods. Genetically modified organisms (GMOs) are particularly concerning, as they're engineered to withstand higher herbicide applications, increasing residue levels and potential health impacts.
Herbicide manufacturers promote GMO crops to enhance yields and sales, but this often comes at the expense of consumer health. In functional medicine practices, we routinely address these exposures, yet skeptics may downplay them, claiming "GMOs and pesticides are safe with no proven harm." Ironically, those same individuals frequently deal with metabolic syndromes, joint pain, and polypharmacy.
Fluoride, added to tap water and toothpaste in places like the U.S. for dental health, is another concern. Dental amalgam fillings release small amounts of mercury over time—a heavy metal that accumulates in the body. Dismissive arguments like "it's only a tiny amount" or "98% is safe" overlook the potential impact of that remaining 2%, which can be significant for sensitive individuals. Health risks, no matter how small, deserve attention rather than lazy dismissal.
Endocrine disruptors, such as BPA and phthalates, lurk in everyday items like plastic water bottles, Styrofoam cups, and instant noodle packaging. Even after BPA's risks were publicized, it persisted in products for years. Items from regions with lax regulations often exceed safety standards. Moreover, "safe" regulatory levels may not truly be harmless—actual safe thresholds are often far lower. Cosmetics can also contain these toxins, so vigilance is key.
These toxins disrupt hormone signaling by blocking receptors. Similar to insulin resistance, where blocked insulin receptors lead to poor glucose control, clogged thyroid hormone receptors can cause thyroid overactivity, enlargement, or nodules. Blocked estrogen receptors may result in irregular periods, endometriosis, or breast lumps. Issues with leptin receptors can stall weight loss and aggravate skin conditions like acne or psoriasis. This explains why some people report that low-carb high-fat diets or fasting "ruined" their bodies and advise against them.
However, if you're experiencing these challenges, abandoning the diet isn't always the answer—proceeding with awareness is. Identifying the root cause opens the door to solutions. For mild, manageable side effects, pushing harder with stricter fasting might seem tempting, but it often backfires.
Instead, if symptoms arise, consider pausing the diet temporarily. Prioritize detoxification to clear toxins, then resume. This methodical approach proves more efficient long-term. A hair mineral analysis at a hospital can detect heavy metal levels, or a functional medicine clinic can provide targeted detox protocols.
At home, enhance mineral intake to displace heavy metals, as they vie for the same bodily sites. Avoid megadoses; adhere to recommended amounts and increase gradually if tolerated. Salt, a mineral itself, can be helpful—try adding a teaspoon to water, but start small to prevent exacerbating side effects.
Begin with one teaspoon of salt or the standard supplement dose, scaling up to two or three if needed. For intermittent fasting, incorporate periodic carb refeed days using whole, plant-based foods rather than processed options.
Above all, if side effects are intense, seek guidance from a functional medicine specialist. A single consultation can equip you with lifelong knowledge. Don't navigate blindly—professional insight can illuminate the path.
Low-carb high-fat diets, intermittent fasting, and even vegetarian approaches offer tremendous benefits, but side effects from toxins and nutrient imbalances can arise. By addressing these underlying issues first, you'll find it much easier to reach your health objectives. I hope this article has shed light on the reasons behind these side effects and empowered you with smart strategies to overcome them. If it resonated, feel free to share your thoughts or experiences below. Stay tuned for more practical health advice!
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