Effects of a four-week very low-carbohydrate high-fat diet on biomarkers of inflammation: Non-randomised parallel-group study.

BACKGROUND: It is commonly assumed that increased dietary fat and/or caloric excess induces chronic inflammatory processes, since the association between obesity and chronic adipose tissue with systemic inflammation has been shown previously. As far as we know, the reported health benefits of a VLCHF or ketogenic diet have not adequately involved an evaluation of biomarkers of inflammation. AIM: This study investigated the effects of a four-week very low-carbohydrate high-fat (VLCHF) diet in healthy young individuals on biomarkers of inflammation. METHODS: Eighteen moderately trained males (age 23.8 ± 2.1 years) were assigned to two groups. One group switched to a non-standardised VLCHF diet for four weeks, while the second group remained consuming their normal habitual diet (HD). Biomarkers of inflammation (adiponectin, leptin, resistin and interleukin-6) and substrate metabolism (fasting glucose and triacylglyceride concentrations) were analysed from blood at baseline and after four weeks. RESULTS: There was moderate evidence for substantial changes in leptin serum concentrations in the VLCHF group, with small to large decreases compared to the HD group after four weeks (effect size = 0.78, 95% CI 0.42, 0.93, p = 0.008; Bayes Factor10 = 5.70). No substantial between-group change differences over time were found across any other biomarkers. CONCLUSIONS: A four-week period of consuming a VLCHF diet in healthy young men was not associated with any considerable changes in markers of inflammation but showed evidence for lowered serum leptin concentrations relative to the HD group.

Effects of a 4-Week Very Low-Carbohydrate Diet on High-Intensity Interval Training Responses.

The purpose of the study was to examine the effects of altering from habitual mixed Western-based (HD) to a very low-carbohydrate high-fat (VLCHF) diet over a 4-week timecourse on performance and physiological responses during high-intensity interval training (HIIT). Eighteen moderately trained males (age 23.8 ± 2.1 years) consuming their HD (48 ± 13% carbohydrate, 17 ± 3% protein, 35 ± 9% fat) were assigned to 2 groups. One group was asked to remain on their HD, while the other was asked to switch to a non-standardized VLCHF diet (8 ± 3% carbohydrate, 29 ± 15% protein, 63 ± 13% fat) for 4 weeks. Participants performed graded exercise tests (GXT) before and after the experiment, and an HIIT session (5x3min, work/rest 2:1, passive recovery, total time 34min) before, and after 2 and 4 weeks. Heart rate (HR), oxygen uptake (V̇O2), respiratory exchange ratio (RER), maximal fat oxidation rates (Fatmax) and blood lactate were measured. Total time to exhaustion (TTE) and maximal V̇O2 (V̇O2max) in the GXT increased in both groups, but between-group changes were trivial (ES ± 90% CI: -0.1 ± 0.3) and small (0.57 ± 0.5), respectively. Between-group difference in Fatmax change (VLCHF: 0.8 ± 0.3 to 1.1 ± 0.2 g/min; HD: 0.7 ± 0.2 to 0.8 ± 0.2 g/min) was large (1.2±0.9), revealing greater increases in the VLCHF versus HD group. Between-group comparisons of mean changes in V̇O2 and HR during the HIIT sessions were trivial to small, whereas mean RER decreased more in the VLCHF group (-1.5 ± 0.1). Lactate changes between groups were unclear. Adoption of a VLCHF diet over 4 weeks increased Fatmax and did not adversely affect TTE during the GXT or cardiorespiratory responses to HIIT compared with the HD.