Are there sex differences in the variability of fasting metabolism?

• Published in: Journal of applied physiology (1985) Vol. 136; no. 6; pp. 1450 - 1459
• Main Authors: Bradshaw, Louise, Buniam, Jariya, Betts, James A, Gonzalez, Javier T
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.06.2024
• Subjects: 17β-Estradiol; Adult; Basal Metabolism - physiology; Blood Glucose - metabolism; Body mass; Coefficient of variation; Cross-Over Studies; Esterification; Estradiol - blood; Fasting; Fasting - blood; Fasting - metabolism; Female; Females; Humans; Insulin - blood; Insulin - metabolism; Lactic Acid - blood; Lactic Acid - metabolism; Male; Males; Metabolic rate; Metabolism; Metabolites; Middle Aged; Progesterone; Progesterone - blood; Progesterone - metabolism; Secondary analysis; Sex Characteristics; Sex differences; Sex Factors; Sex hormones; Short Report; Triglycerides; Triglycerides - blood; Variance analysis; Young Adult; variability; metabolism; sexual dimorphism
• ISSN: 8750-7587; 1522-1601; 1522-1601
• DOI: 10.1152/japplphysiol.00053.2024

There is evidence across species and across many traits that males display greater between-individual variance. In contrast, (premenopausal) females display large within-individual variance in sex hormone concentrations, which can increase within-individual variance in many other parameters. The latter may contribute to the lower representation of females in metabolic research. This study is a pooled secondary analysis of data from seven crossover studies to investigate the between-individual and the within-individual variance in fasting plasma metabolites, resting metabolic rate (RMR), and body mass. Females demonstrated higher within-individual variability of plasma 17β-estradiol [coefficient of variation (CV): 15 ± 15% for males vs. 38 ± 34% for females, < 0.001] and progesterone concentrations (CV: 13 ± 11% for males vs. 52 ± 51% for females, < 0.001) but there were no meaningful differences in the variability of plasma glucose (CV: 4 ± 3% for males vs. 5 ± 5% for females), insulin, lactate, triglycerides (CV: 15 ± 9% for males vs. 15 ± 10% for females), and esterified fatty acid concentrations or in RMR and body mass (CV: 0.43 ± 0.34% for males vs. for 0.42 ± 0.33% females; > 0.05 for all outcomes). Males displayed higher between-individual variance in RMR compared with females (SD: 224 kcal·day for males vs. 151 kcal·day for females). In conclusion, these data do not provide evidence that females show greater within-individual variability in many fasting metabolic variables, RMR, or body mass compared with males. We conclude that including females in metabolic research is unlikely to introduce greater within-individual variance when using the recruitment and control procedures described in these studies. To investigate the within-individual variability in metabolic parameters in males and females, we performed a pooled secondary analysis of fasting blood samples, resting metabolic rate, and body mass from seven crossover studies. We found a greater day-to-day variation in 17β-estradiol and progesterone in females compared with males but no meaningful difference in within-individual variability of fasting plasma glucose, insulin, lactate, triglycerides, NEFA, resting metabolic rate, or body mass between females and males.