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BackgroundChronic postprandial hyperlipidemia is associated with increased risk of cardiovascular disease (CVD). Very low carbohydrate (VLC) diets are a popular choice for weight‐loss, but acute effects of VLC diets on postprandial plasma fatty acids have not been tested.MethodsFour healthy, normal weight adults participated in a randomized crossover feeding study. Subjects consumed a standard diet [51% carbohydrate (CHO), 14% protein, 35% fat] for 3 days. On day 4 participants consumed either VLC (4%) or high CHO [HC (58%)] meals. Subjects then repeated standard diet and alternate test meals. Pre‐ and postprandial concentrations of plasma triglycerides (TG) and individual fatty acids were analyzed by modified Wahlefeld method and GC/MS, respectively. Differences between diets were compared by paired t‐tests.ResultsTG were significantly higher on the VLC diet compared to the HC diet (Area under the curve for TG: VLC 1217±420 and HC1033±369 mg·h/dL, p=0.03). Saturated fatty acids (SFA) were significantly higher 4 hours after a VLC meal (VLC 19960±1094 vs HC 12193±906 µmol/L, p=0.020). There was no difference in postprandial omega‐6 or omega‐3 fatty acid concentrations between diets.ConclusionsPlasma‐TG and SFA were higher after the VLC meals when compared to the HC meals. Chronic elevation of postprandial lipids may contribute to the development of CVD. Supported by the Graduate Programs in Human Nutrition, PHS Grant UL1 RR024140, and National Center for Complementary and Alternative Medicine (R21 AT002753‐01).

Macronutrient consumption influences respiratory quotient (RQ) and energy expenditure (EE) in vivo. EE may be higher after LC than high carbohydrate (HC) meals which may confer a metabolic advantage that contributes to greater weight loss. We used a randomized crossover trial to test the hypothesis that LC meals result in higher postprandial EE and lower RQ than HC meals. Eight healthy, normal weight adults consumed a run‐in diet for 3 days and were admitted into the Clinical Research Center on the 4th day. Resting EE was measured for 45 minutes by indirect calorimetry, then subjects ate a HC or LC meal and postprandial EE was measured for 45 minutes every hour for 4 hr. A 2nd meal of the same composition was consumed and postprandial EE was measured for an additional 4 hr. This procedure was repeated after a >3 day washout period when subjects ate meals of the alternate diet. Postprandial AUC was calculated for EE, RQ, CO2 production (VCO2) and oxygen consumption (VO2) after the entire 9 hr period. Differences between diets in AUC for each variable were measured by one‐tailed paired t‐tests. After consumption of the LC meals, AUC of VO2 was not different but AUC of VCO2 was lower (2.17±1.94 vs 2.04±1.50, p<0.01) resulting in a lower AUC of RQ (4.10±0.63 vs 4.65±0.58; p<0.01). There was no difference in AUC EE over the 9 hr studied; however, the patterns of change of EE suggest that there may be differences if studied for longer periods of time.

People following low carbohydrate (LC) diets report "food disinterest" that may lead to greater weight loss than other diets. Changes in weight regulation hormones that affect hunger and satiety may contribute to this heightened response. A random‐order, crossover design was used to test the hypothesis that acute consumption of LC meals reduces postprandial insulin, leptin, and ghrelin concentrations compared to high complex carbohydrate (HC) meals.Seven normal‐weight adults completed two 4‐day controlled dietary phases. Subjects consumed a standard diet for 3 days and LC (4% CHO) or HC (58% CHO) meals providing 10 kcal/kg on day 4. Insulin, leptin, and ghrelin were measured in blood samples hourly for 9.5 h after breakfast. Area under the curve (AUC) and patterns of change for each analyte were determined with differences between diets compared using paired t‐tests and Wilcoxon Signed‐Rank tests.AUC's for insulin (91±13 vs 259±30 μIU ·h/ml, p=0.0002) and leptin (4±0.7 vs 5±1.0 ng·h/ml·kg fat mass, p=0.03) were significantly lower after the LC than the HC diets. The linear term was significant for leptin, p=0.03. The linear (LC), quadratic and quartic (HC) terms were significant for ghrelin, p=0.02.Consumption of LC and HC meals resulted in different patterns of change for all analytes, and lower AUCs for insulin and leptin. These differences may explain the food disinterest and heightened weight loss associated with LC diets.