Free fatty acid theory of insulin resistance

Free fatty acid theory of insulin resistance holds that the inability of cells to oxidize glucose—the hallmark of type 2 diabetes—is driven primarily by elevated free fatty acids (FFAs) in the bloodstream, not by excess sugar. 3 Peat explained that this phenomenon was described biochemically in the 1960s by P.J. Randle, who demonstrated that increasing fatty acids directly blocks glucose oxidation. 6 Peat consistently rejected the term “Randle cycle,” insisting there is no true cycle but simply a competition for oxidation: when FFAs are high, cells oxidize fats and ignore glucose, causing blood sugar to rise. 2 This was starkly demonstrated in hospitals when patients receiving intravenous soy oil emulsions became hyperglycemic within 15 minutes. 2

The mechanism is a self-perpetuating stress cascade. When FFAs block glucose oxidation, cells signal for more fuel, prompting the liver to produce additional glucose and worsening hyperglycemia. 2 Peat argued that the resulting high blood sugar is a compensatory adjustment, not the root cause of the pathology. 2 The glucose that does enter cells cannot proceed through mitochondrial respiration and is instead wasted as lactic acid, which the liver converts back into glucose, further straining the system. 2 Dinkov has written that this competition means cells can only process one fuel at a time, and that lowering FFAs—through inhibiting lipolysis—allows cells to resume glucose oxidation and reverses insulin resistance, barring other enzymatic defects. 3 Roddy notes that stress hormones like adrenaline, cortisol, and estrogen are all lipolytic, liberating FFAs into the blood and directly inhibiting glucose use to spare it for the brain and muscles. 5

Peat drew a critical distinction between fat types, arguing that the theory is fundamentally a problem of polyunsaturated fatty acids (PUFAs). He stated that PUFAs systematically turn on the very stress hormones that block energy production, creating a vicious cycle. 1 While all FFAs can block glucose oxidation acutely via the Randle effect, PUFAs produce long-range damage by spontaneously oxidizing and forming advanced glycation end-products (AGEs), which are more powerfully driven by PUFAs than by glucose itself. 7 In contrast, Peat noted that even when a very high sugar diet forces the body to synthesize new fats, these endogenously produced fats are saturated or monounsaturated, and they lower the toxic effects of free radicals rather than promoting them. 6 He later clarified that coconut oil, rich in saturated fats, increases oxidative metabolism and is protective against diabetes, partly because its shorter fatty acids oxidize like sugar and partly because it displaces the antimetabolic effects of stored PUFAs. 10

The clinical implications reframe diabetes as an endocrine disorder of fat metabolism. Peat recounted a case where a diabetic friend’s gangrenous toes healed completely on thyroid hormone, which lowers stress and FFAs, only to rot again when his doctor withdrew the treatment, repeating this cycle three times. 2 Dinkov has emphasized that insulin resistance is not a fixed cellular defect but a state driven by the environment of elevated FFAs; agents like niacinamide and aspirin can lower FFAs and restore glucose metabolism. 2 Roddy has highlighted evidence that chronic exposure to FFAs destroys insulin-secreting pancreatic beta cells, while glucose infusion can regenerate beta cell mass by 250 percent in days, further implicating fat rather than sugar as the primary toxin. 5 The theory thus posits that the modern epidemic of diabetes tracks the increased consumption of industrial polyunsaturated oils, which block energy production at the cellular level. 2