This study investigates how orally ingested exogenous ketone monoester supplements affect circulating hormone concentrations in healthy young adult males after a single session of resistance exercise. Resistance exercise is known to stimulate an acute increase in the circulating concentration of various hormones that are involved in the regulation of muscle mass, including testosterone, growth hormone (GH), and insulin-like growth factor-1 (IGF-1).

Recently, there has been growing interest in how nutritional supplements impact these natural hormone responses at rest. One such intervention is the oral ingestion of exogenous ketone body supplements. Ketone bodies (i.e., β-hydroxybutyrate (β-HB), acetoacetate (AcAc), and acetone) are naturally occurring compounds that are normally produced by the body during prolonged fasting/starvation, or in response to a "ketogenic" diet (a diet very high in fat and very low in carbohydrates). These ketone body supplements taken in the form of a ketone monoester can quickly raise blood ketone levels without needing to change your diet.

Recent research has shown that the ingestion of exogenous ketone supplements or following a 'ketogenic diet' can alter the concentration of certain hormones measured in blood samples at rest. However, the effects of ketone monoester intake on the exercise-induced elevation in circulating hormones is yet to be explored.

Therefore, the purpose of this study is to examine how elevated β-HB, induced via the ingestion of the ketone monoester (R)-3-hydroxybutyl-(R)-3-hydroxybutyrate, affects blood concentrations of various anabolic hormones, during post-exercise recovery in healthy young adult males, compared to a placebo drink (flavoured water).

A within-subject crossover design will be used for this randomized, double-blind, placebo-controlled study in healthy males to investigate the impact of ketone monoester (KET) intake on circulating (blood) concentrations of 'anabolic' and other hormones. There are two treatment arms in this crossover trial, including one KET arm and one placebo group. A total of 12 participants will be enrolled and undergo both treatment phases with a minimum 7-day washout period between lab visits.

The study will include a screening visit (Visit 1), 10-repetition maximum (10-RM) testing (visit 2), where participants' 10-RM will be determined for each exercise machine used, experimental trial (visit 3), minimum 7-day washout, followed by the phase 2 of the experimental trial (visit 4).

During the experimental trials, participants will arrive to the laboratory in an overnight fasted state, and the KET or placebo drink will then be administered following basal blood collection. Then, participants will perform a lower-body resistance exercise session consisting of 5 sets of 10 repetitions of leg press and 3 sets of 12 repetitions of leg extension/leg curl supersets at 95% of their determined 10-RM. Following exercise, another dose of the nutritional treatment will be administered.

Arterialized blood samples will then be collected at 13 postprandial timepoints during the 1-hour rested period and the 4-hour post-exercise recovery period to measure changes in plasma glucose and insulin concentration. Arterialized blood samples will also be utilized for quantitation of anabolic hormones, including testosterone, IGF-1, GH, cortisol, luteinizing hormone, sex-hormone binding globulin, dehydroepiandrosterone, estrogen, progesterone, and follicle-stimulating hormone.

Additionally, changes in capillary blood β-HB concentration will be assessed throughout the trials by collecting capillary blood samples at baseline and 11 postprandial timepoints during the 1-hour rested period and the 4-hour post-exercise recovery period.

Inclusion Criteria:

• Healthy adult male participants who are 18-40 years of age (inclusive).
• BMI >18.5 and <30.0 kg/m2
• Recreationally active (at least of 150 minutes of activity/week).
• Has maintained stable use of medication and supplements (which are not limited by the exclusion criteria), stable dietary and lifestyle habits, and stable body weight, for the last 3 months prior to screening and agree to maintain them throughout the study.
• Be willing to entirely avoid alcohol consumption 48 hours prior to the test days.
• Willing and able to agree to the requirements and restrictions of this study, be willing to give voluntary consent, be able to understand and read the questionnaires, and carry out all study-related procedures.

Exclusion Criteria:

• Individuals with metabolic disorders including: Type I or Type II diabetes.
• Individuals with a history of thrombosis / cardiovascular disease, endocrine disorders
• Individuals with knee injuries (i.e., ACL injuries).
• Individuals with a positive medical history of unstable thyroid disease (i.e., hypothyroidism, hyperthyroidism, hyperparathyroidism, and hypoparathyroidism) and immune disorders.
• Individuals who have used tobacco products within the last 6 months.
• Chronic usage of medications known to modulate hormone levels (i.e. corticosteroids and hormone replacement therapy (HRT)) in the last 6 months.
• Current use of ketone supplements or adherence to a ketogenic diet.
• Formal or regular weightlifting activity within the last year.

Cis males

Participants, Investigators and Outcome Accessors will be blinded to the intervention and control drinks. The drinks will be flavor matched and provided in an opaque bottle. An individual not involved with the study data collection, analysis and interpretation will be designated as a study blinder and randomizer.