This study examines whether resting metabolic rate (RMR)-the amount of energy the body uses at rest-is similar between biological parents and their adult children (aged 18 years and older). RMR is the largest component of daily energy expenditure and plays an important role in body weight regulation and overall metabolic health.

Participants from the same family will undergo a single testing session in a metabolic laboratory. RMR will be measured using indirect calorimetry under standardized conditions, along with body composition assessment and basic health information.

The primary goal is to determine whether RMR is correlated within families. The study will also assess whether these similarities remain after accounting for differences in body composition, age, and sex.

This observational study will help improve understanding of how metabolism varies between individuals and the extent to which these differences may be influenced by familial or inherited factors. Findings may contribute to future research on personalized nutrition, obesity risk, and metabolic health.

Resting metabolic rate (RMR) represents the largest component of total daily energy expenditure and is a key determinant of energy balance, weight regulation, and metabolic health. While factors such as fat-free mass, fat mass, age, and sex explain a substantial portion of interindividual variability in RMR, evidence from family and genetic studies suggests a significant hereditary component.

Classic family-based studies have reported moderate parent-offspring correlations in RMR, with heritability estimates ranging from approximately 30% to 50%. More recent genetic and epidemiological research supports these findings, indicating that a meaningful proportion of variability in metabolic rate is influenced by genetic and familial factors. However, most direct parent-child calorimetry studies were conducted decades ago, and contemporary data using standardized methodologies in adult populations remain limited.

This study is designed as a cross-sectional observational family study to evaluate the relationship between RMR in biological parents and their adult children (≥18 years). Studying adult offspring is important because metabolic rate stabilizes after growth and development, allowing for more accurate assessment of underlying physiological and familial patterns.

Participants will include families consisting of one or both biological parents (aged 40-60 years) and at least one adult child. All participants will undergo RMR measurement using a validated indirect calorimetry system under standardized laboratory conditions, including overnight fasting, avoidance of recent exercise, and controlled environmental conditions. Body composition (including fat-free mass and fat mass) will be assessed using bioelectrical impedance analysis under standardized conditions.

The primary outcome is the correlation between parent and offspring RMR. Secondary analyses will evaluate whether these associations persist after adjustment for body composition, age, and sex, and will explore potential differences between same-sex and opposite-sex parent-child pairs. Statistical analyses will include correlation coefficients, multivariable regression models, and approaches that account for clustering within families.

This study involves minimal risk and non-invasive procedures. All data will be collected in a controlled research setting, anonymized, and handled in accordance with institutional ethical standards.

By providing updated evidence on familial patterns of metabolic rate, this study aims to improve understanding of interindividual variability in metabolism and contribute to future research on metabolic health, obesity susceptibility, and personalized approaches to nutrition and lifestyle interventions.

Inclusion Criteria:

• Biological parent-adult child pairs
• Adult children aged ≥18 years
• Parents aged 40-60 years
• Ability to comply with study procedures, including fasting and resting conditions
• Generally healthy individuals without acute illness

Exclusion Criteria:

• Current weight loss or active dieting
• Known metabolic disorders (e.g., thyroid disease)
• Use of medications affecting metabolic rate
• Pregnancy
• Acute illness at the time of testing
• Inability to comply with pre-test requirements (e.g., fasting, avoiding exercise or caffeine)

Biological parent-adult child families recruited from the general population. Participants are generally healthy adults, including parents aged 40-60 years and their adult children aged 18 years and older, without known metabolic disorders.