BACKGROUND

Single doses of exogenous ketone salts (KS) transiently increase circulating beta-hydroxybutyrate (BHB) (∼1 mM; 1-2 h) regardless of starting levels of ketosis; however, no studies have explored how sustained use of KS influences measures of ketonemia and glycemia.

OBJECTIVES

To determine the response to a hypocaloric, well-formulated ketogenic diet (KD), with and without the inclusion of two daily racemic KS doses (6 g R-BHB + 6 g S-BHB per serving) on 1) daily fasting capillary R-BHB and glucose (R-BHB/GLU), 2) bi-weekly 13 h diurnal BHB and glucose (R-BHB/GLU), 3) three-hours post-KS ingestion kinetics (R-BHB), and 4) bi-weekly fasting plasma enantiomer-specific BHB (R/S-BHB).

METHODS

Non-diabetic adults with overweight and obesity were randomized to receive a precisely measured hypocaloric KD (∼75 %en of maintenance) for six weeks, supplemented twice-daily with KS or placebo (PL). A non-randomized comparison group was provided an isonitrogenous/isoenergetic low-fat diet (LFD). All meals were provided to subjects. Capillary blood was collected daily to measure R-BHB/GLU and hourly for R-BHB/GLU. Plasma was collected to measure R/S-BHB, insulin, fasting glucose, and insulin resistance (HOMA-IR). Total AUC was calculated using the trapezoidal method.

RESULTS

Mean R-BHB increased significantly during KD + PL (1.0 mM BHB), an effect enhanced 26% during KD + KS. GLU AUC was -6% lower during KD + KS versus LFD. Mean R-BHB increased 40% in KD + KS versus KD + PL, whereas GLU decreased 13% during both KDs versus LFD. R-BHB peaked (Δ: ∼1 mM) 1 h after the morning KS dose, but not following the afternoon dose. Both R/S-BHB increased during KD independent of KS inclusion. R-BHB was 50-times greater compared to S-BHB, and the KS augmented S-BHB 50% more than PL. Fasting insulin and HOMA-IR decreased after 14 days independent of diet.

CONCLUSIONS

A hypocaloric KD was effective at reducing diurnal glucose compared to a LFD independent of weight loss, but twice-daily racemic KS ingestion during KD augmented ketonemia, both as R- and S-BHB, and decreased mean fasting glucose beyond a KD alone. The hypoglycemic effects of KD in combination with exogenous ketones merit further investigation.