Plasma β‐hydroxybutyrate concentrations in young adult females after a high‐fat meal under normoxaemia, intermittent hypoxaemia and continuous hypoxaemia: An exploratory analysis

Abstract Hypoxaemia occurs in intermittent forms, such as obstructive sleep apnoea, and in continuous forms, such as at high altitude, and is increasingly recognized as a modulator of cardiometabolic risk. Although hypoxaemia alters postprandial glucose and lipid metabolism, its effects on ketone bodies remain unclear. Using a randomized crossover design, we examined whether 6 h of normoxaemia or intermittent hypoxaemia (15 hypoxaemic cycles/h targeting ∼85% peripheral oxyhaemoglobin saturation with 100% medical‐grade nitrogen) alters plasma β‐hydroxybutyrate (BHB) concentrations in 12 young adult females (mean [SD]: 21 [3] years) following a high‐fat meal (33% of estimated daily energy requirements; 59% of energy from fat). In a follow‐up session, a subset ( n = 8) completed 6 h of continuous hypoxaemia (fraction of inspired oxygen ∼12.0% in a normobaric chamber). Postprandial data were analysed using baseline‐adjusted linear mixed‐effects models, with Bonferroni post hoc tests. A time × condition interaction ( P = 0.010) indicated that BHB concentrations at 360 min were higher during continuous hypoxaemia (0.247 mmol/L; 95% CI: 0.218–0.275) than normoxaemia (0.176 mmol/L; 95% CI: 0.153–0.200; P Bonferroni = 0.029) and intermittent hypoxaemia (0.163 mmol/L; 95% CI: 0.139–0.186; P Bonferroni = 0.002), representing increases of 13.0% and 14.2% in estimated marginal means, respectively. This response was accompanied by higher postprandial plasma glucose and triglyceride concentrations during continuous hypoxaemia than during normoxaemia and intermittent hypoxaemia ( P Bonferroni ≤ 0.002), despite similar plasma insulin and non‐esterified fatty acid responses across conditions ( P ≥ 0.081). These findings indicate that continuous hypoxaemia increases late postprandial plasma BHB concentrations in young adult females.