BayouHealth | Insulin Resistance: Looking Beyond the Diet for Cause

BY SHANNON DAHLUM, FDN-P

Insulin resistance has become a major health concern, linked to a growing epidemic of obesity, metabolic syndrome, type 2 diabetes, and other chronic health conditions. While diet— especially excessive sugar and refined carbohydrate intake—is often blamed as the primary driver, the reality is far more complex. Insulin resistance is not solely a result of poor dietary choices; it’s influenced by a range of physiological and biochemical imbalances that are frequently overlooked. Nutrient deficiencies, hormonal imbalances, gut health issues, liver function, adrenal health, fungal overgrowth, and even dietary fat composition all play significant roles in how the body responds to insulin. Understanding these underlying factors and addressing them can help restore metabolic balance and improve insulin sensitivity more effectively than dietary changes alone.

Insulin is a hormone produced by the pancreas that allows cells to take up glucose from the bloodstream and use it for energy. In insulin resistance, the cells become less responsive to insulin’s signals, leading to elevated blood glucose levels and prompting the pancreas to produce more insulin in an attempt to maintain balance. Over time, this increased insulin production can contribute to weight gain, increased inflammation, and ultimately, the development of type 2 diabetes if left unchecked. While insulin resistance is often linked to poor diet and obesity, a range of deeper physiological and biochemical factors can also drive this dysfunction.

One of the most overlooked drivers of insulin resistance is excessive saturated fat intake. While low-carb and ketogenic diets have gained popularity for improving blood sugar control and promoting weight loss, their reliance on high saturated fat intake can paradoxically worsen insulin resistance in the long term.

Saturated fats are known to increase the concentration of free fatty acids (FFAs) in the bloodstream. Elevated FFAs promote the storage of fat within muscle and liver cells, which interferes with insulin signaling and reduces the ability of cells to take up glucose. High saturated fat intake also increases inflammatory markers and oxidative stress, which further impairs insulin receptor function.

Ketogenic and very low-carb diets (VLCDs) can initially improve blood sugar levels because they reduce the body’s reliance on glucose, causing fasting glucose and insulin levels to drop. However, the long-term impact of sustained high saturated fat intake includes increased fat storage in muscle and liver tissue, elevated fasting insulin levels despite low blood glucose, reduced muscle glucose uptake, and increased liver insulin resistance.

A diet high in monounsaturated fats (like olive oil and avocados) and polyunsaturated fats (like fatty fish, walnuts, and flaxseed) appears to improve insulin sensitivity more effectively than one dominated by saturated fats (like butter, coconut oil, and red meat).

Insulin and glucose regulation pathways rely on various nutrients to function properly, and deficiencies in key nutrients, like thiamine (also known at B1) can be a causative factor of dysfunction. Thiamine is essential for glucose metabolism. It acts as a cofactor for enzymes involved in the citric acid cycle, which helps convert carbohydrates into energy. A deficiency in B1 can impair glucose metabolism and increase oxidative stress, making cells less responsive to insulin. Studies have shown that thiamine deficiency is common in individuals with metabolic syndrome and type 2 diabetes. Supplementing with thiamine has been shown to improve glucose metabolism and reduce insulin resistance.

Candida overgrowth and mold toxicity are two overlooked causes of thiamine depletion. Candida produces acetaldehyde, a toxic byproduct that binds to thiamine and makes it unavailable for use in cellular energy production. Mold exposure can similarly impair thiamine levels by increasing oxidative stress and depleting cellular reserves of key B vitamins.

When thiamine levels are low, glucose metabolism becomes impaired, which leads to higher circulating glucose levels and increased insulin production. This creates a vicious cycle where poor glucose regulation feeds further fungal overgrowth, since Candida thrives on sugar.

Signs of thiamine depletion due to Candida or mold toxicity include, fatigue, brain fog, muscle weakness, nerve pain or tingling, and sugar cravings.

Addressing fungal overgrowth by supporting healthy digestion (ensuring healthy stomach acid production, bile flow, and digestive enzyme production), supporting detoxification pathways, and potentially by including antifungal protocols (such as caprylic acid, oregano oil, and probiotics), can improve thiamine status and reduce insulin resistance.

Niacin is another vitally important nutrient for supporting this process. It is needed for the production of NAD+ (nicotinamide adenine dinucleotide), a critical molecule involved in cellular energy production and glucose metabolism. Low levels of NAD+ impair insulin signaling and mitochondrial function, contributing to insulin resistance. However, excess niacin supplementation can also impair glucose control by increasing insulin resistance, so balance is key.

Estrogen plays a complex role in glucose metabolism. While physiological levels of estrogen can enhance insulin sensitivity, estrogen dominance—characterized by high estrogen levels relative to progesterone—can worsen insulin resistance. Estrogen dominance increases inflammation, raises cortisol levels, and promotes fat storage, particularly in the abdominal area. Elevated estrogen levels also reduce thyroid function, which can further impair glucose metabolism and insulin sensitivity.

Factors that contribute to estrogen dominance include, poor liver detoxification (inability to clear excess estrogen), exposure to xenoestrogens (from plastics, personal care products, pesticides), and low progesterone levels (due to stress, poor ovulation, or perimenopause).

The health of the gut lining also directly influences metabolic health. A compromised gut barrier (leaky gut) allows bacterial toxins known as lipopolysaccharides (LPS) to enter the bloodstream. LPS triggers an immune response and increases systemic inflammation, which interferes with insulin signaling at the cellular level.

LPS and inflammation from leaky gut can impair insulin receptor function, making cells less responsive to insulin even when blood glucose levels are elevated. Healing the gut through probiotic support, increased fiber intake, and reducing inflammatory foods can decrease inflammation stemming from the gut and improve insulin sensitivity.

The liver plays a central role in glucose metabolism and insulin sensitivity. When the liver becomes congested due to poor detoxification, fatty liver disease, or excessive alcohol consumption, it struggles to regulate glucose levels and respond to insulin.

Supporting liver health through targeted detoxification (such as NAC, milk thistle, and dandelion root) and reducing processed fats and alcohol can enhance insulin sensitivity.

Blood Markers to Assess Insulin Sensitivity
To evaluate insulin sensitivity and metabolic health, the following blood markers are useful:
• Fasting Blood Glucose – Optimal range: 75–85 mg/dL
• Fasting Insulin – Optimal range: 2–6 μIU/mL
• HbA1c– Optimal range: 4.8–5.2%

Helpful Nutritional Approaches Based on Lab Markers
• High Fasting Insulin and Glucose – If elevated, intermittent fasting (12–16 hours) may help reduce insulin resistance by lowering insulin production and supporting liver detoxification.
• Low Fasting Insulin and Glucose – If low, fasting is not advisable. Small, balanced meals rich in protein, fat, and complex carbs every 3–4 hours are more beneficial.

Insulin resistance is far more complex than just poor diet and weight gain. Saturated fat intake, nutrient deficiencies, estrogen dominance, gut health, adrenal function, liver congestion, and fungal overgrowth all play significant roles in glucose metabolism. A comprehensive approach that includes balancing fats, supporting gut health, restoring nutrient levels, and improving liver function will improve insulin sensitivity more effectively than restrictive dieting alone.