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.

Circulating fatty acid profiles are linked to cardiovascular disease risk and mortality. Short-term interventions suggest that low-carbohydrate diets (LCDs) promote cardioprotective shifts in circulating fatty acids in obesity. We examined whether a 6-mo, non-calorie-restricted, LCD high in fat similarly improves circulating fatty acid composition in adults with type 2 diabetes. In an open-label, randomized, controlled trial, 71 individuals with type 2 diabetes were randomly assigned 2:1 to an LCD [maximum of 20 E% (energy per cent) carbohydrates] or a control diet (50-60 E% carbohydrates) for 6 mo with no restriction in energy intake. The prespecified secondary outcomes were the mean difference in change between groups in serum phospholipid fatty acids in weight percentage (wt%) measured by gas chromatography and reported as 95% confidence intervals (CIs) and significance adjusted for multiple comparisons (q value). LCD reduced total saturated [-0.6 (CI: -0.9, -0.2)] and monounsaturated fatty acids [-0.9 (CI: -1.4, -0.3)] and increased total polyunsaturated fatty acids [1.3 (CI: 0.6, 2.0)] compared with the control diet (all q < 0.05). Importantly, LCD reduced palmitoleic acid (16:1n-7) [-0.13 (CI: -0.21, -0.06)], a marker of de novo lipogenesis, by 23% and dihomo-γ-linolenic acid (20:3n-6) [-0.38 (CI: -0.67, -0.09)] by 12%, whereas it increased arachidonic acid (20:4n-6) [1.1 (CI: 0.3, 2.0)] by 9% compared with the control diet (all q < 0.05). Moreover, the LCD improved estimated desaturase activities by lowering stearoyl-coenzyme A desaturase 1 [-0.5 (CI: -0.7, -0.2)] and Δ6 desaturase [-0.6 (CI: -0.9, -0.2)] and increasing Δ5 desaturase [1.05 (CI: 0.3, 1.79)] activities, respectively (all q < 0.01). These changes occurred despite a 2.6-fold higher intake of saturated fatty acids in the LCD group. A 6-mo, non-calorie-restricted LCD modified the circulating composition of fatty acids in adults with type 2 diabetes in a manner consistent with a potentially favorable cardioprotective profile. This trial was registered at www. gov as NCT03068078.