Six-month low-carbohydrate diet shifts circulating fatty acids toward a potentially cardioprotective profile in type 2 diabetes
In a 6-month randomized controlled trial of 71 adults with type 2 diabetes, a non-calorie-restricted low-carbohydrate diet (≤20% energy from carbs) modified circulating fatty acid composition—reducing saturated and monounsaturated fatty acids while increasing polyunsaturated fatty acids, even though saturated fat intake was 2.6-fold higher in the low-carb group.
Circulating fatty acid profiles are linked to cardiovascular disease risk and mortality. This 6-month open-label randomized controlled trial enrolled 71 adults with type 2 diabetes and assigned them 2:1 to either a low-carbohydrate diet (LCD; maximum 20 E% carbohydrates) or a control diet (50–60 E% carbohydrates), with no restriction on total energy intake.
The LCD group reduced total saturated fatty acids by 0.6 wt% and monounsaturated fatty acids by 0.9 wt%, while increasing polyunsaturated fatty acids by 1.3 wt%, compared with the control group (all q < 0.05). More specifically, the LCD reduced palmitoleic acid (a marker of de novo lipogenesis) by 23% and dihomo-γ-linolenic acid by 12%, while increasing arachidonic acid by 9%. The LCD also improved estimated desaturase enzyme activities in a pattern associated with reduced metabolic stress. Notably, these cardioprotective shifts in fatty acid composition occurred despite the LCD group consuming 2.6-fold more saturated fat overall, suggesting that the carbohydrate restriction itself—rather than fat reduction—drove the favorable changes. A limitation is the open-label design, which does not fully control for behavioral or expectation effects.
The trial measured serum phospholipid fatty acids by gas chromatography, a direct and specific marker of circulating fatty acid composition. Beyond the headline findings, the LCD improved stearoyl-coenzyme A desaturase 1 activity (lowered by 0.5 units) and Δ6 desaturase activity (lowered by 0.6 units), while increasing Δ5 desaturase activity (increased by 1.05 units)—enzyme shifts that reflect reduced hepatic stress and improved lipid remodeling. The reduction in palmitoleic acid is particularly relevant because elevated palmitoleic acid is independently associated with insulin resistance and cardiovascular risk; a 23% reduction represents a substantial metabolic shift. The study used no calorie restriction, which is pragmatically important because it suggests the fatty acid changes were driven by carbohydrate reduction itself, not by weight loss or energy deficit. The open-label design (participants knew their group assignment) is a limitation, though the biochemical outcomes (fatty acid profiles) are objective. Effect sizes for individual fatty acids were modest in absolute terms (0.1–2 wt%), but the pattern across multiple markers suggests a coherent metabolic direction.
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- Effect of a 6-month low-carbohydrate diet on the circulating fatty acid composition in patients with type 2 diabetes: a secondary analysis of an open-label randomized controlled trial. — The American journal of clinical nutrition (Read the original)