Total Energy Expenditure in Healthy Chinese Populations: A Nationwide Study Using the Doubly Labelled Water Method

Condition(s) studied

Study summary

Between 1990 and 2022, the global prevalence of obesity more than doubled, representing a critical public health concern. China has mirrored this trend, with rapidly increasing rates of overweight and obesity across all age groups. According to the 'Report on Chinese Residents' Nutrition and Chronic Diseases (2020)', 50.7% of Chinese adults are now classified as overweight or obese. Among children and adolescents aged 6 to 17 years, data from the 'Atlas of Nutrition and Health Status of Chinese Children' indicates that the prevalence of overweight and obesity has reached 26.5%.

Obesity is associated with a broad spectrum of adverse health outcomes across the life course. In children, excess adiposity negatively affects skeletal maturation, neurocognitive development, and psychosocial well-being, while also increasing the likelihood of obesity and metabolic dysfunction in adulthood. In adults, obesity is a major risk factor for a range of non-communicable diseases (NCDs), including type 2 diabetes mellitus, hypertension, cardiovascular disease, non-alcoholic fatty liver disease, osteoarthritis, certain cancers, and all-cause premature mortality. Beyond its health implications, obesity imposes substantial economic and social burdens, including increased healthcare expenditure and reduced workforce productivity.

The etiology of the obesity epidemic is multifactorial and remains under active investigation. Hypotheses center around a chronic imbalance between energy intake and expenditure, driven by behavioral, environmental, and physiological factors. Notably, decreased physical activity associated with sedentary lifestyles and increased consumption of energy-dense, nutrient-poor foods have been implicated as key contributors. However, the relative contributions of reduced energy expenditure versus increased energy intake remain insufficiently quantified at the population level. Accurate assessment of total energy expenditure (TEE) is therefore essential to elucidate the energy dynamics underlying the obesity epidemic.

Current approaches for estimating population-level energy and food requirements are often based on indirect methods with limited precision. The doubly labelled water (DLW) technique, which quantifies TEE through measurement of isotope elimination rates (\^2H and \^18O), remains the gold standard for assessing free-living energy expenditure. However, its application has been predominantly confined to high-income countries with well-established research infrastructure. In contrast, the use of DLW in low- and middle-income countries-including China-remains minimal, resulting in critical data gaps that hinder the development of context-specific dietary recommendations and energy requirement models.

To address these limitations, this study will apply the DLW method to measure TEE in healthy children and adults in China. In parallel, the study will assess key modulators of energy metabolism, including anthropometric and physiological parameters, gut microbiota composition, habitual physical activity, and ambient temperature exposure. The resulting dataset will provide high-resolution, population-specific evidence to inform national dietary reference intakes and support the formulation of evidence-based public health strategies aimed at obesity prevention and metabolic health promotion.

Eligibility

Primary outcome measure(s)

• Height — About 3 minutes.
  Height in meters will be measured by Leicester stadiometer (Seca 217, Germany) and reported to two decimal places.
• Weight — About 5 minutes.
  Weight in kilograms will be measured by TANITA.
• BMI — About 10 minutes (calculated)
  BMI values in kg/m2 will be calculated from weight measured by TANITA and height measured by Leicester stadiometer (Seca 217, Germany).
• Fat mass — About 3 minutes.
  Fat mass in kilograms will be measured by TANITA.
• Fat percentage — About 3 minutes.
  Fat percentage will be measured by TANITA.
• Fat-free mass — About 3 minutes.
  Fat-free mass in kilograms will be measured by TANITA.
• Muscle mass — About 3 minutes.
  Muscle mass in kilograms will be measured by TANITA.
• Total body water — About 3 minutes.
  Total body water in kilograms will be measured by TANITA.
• Waist circumference — About 5 minutes.
  Waist circumference(measured in centimeters) will be obtained using a flexible tape measure following standardized protocols.
• Hip circumference — About 5 minutes.
  Hip circumference(measured in centimeters) will be obtained using a flexible tape measure following standardized protocols.
• Thigh circumference — About 5 minutes.
  Thigh circumference(measured in centimeters) will be obtained using a flexible tape measure following standardized protocols.
• Neck circumference — About 5 minutes.
  Neck circumference(measured in centimeters) will be obtained using a flexible tape measure following standardized protocols.
• Blood pressure — About 10 minutes.
  Blood pressure will be measured using a standardized blood pressure monitor, with recordings of both systolic and diastolic values.
• Heart rate — About 10 minutes.
  Heart rate will be measured in using a standardized blood pressure monitor.
• Abdominal fat — About 20 minutes.
  Abdominal fat will be measured in using a portable ultrasound device (DW-360).
• Bone mineral density — About 20 minutes.
  Bone mineral density will be measured using the Dual-energy X-ray Absorptiometry (DXA) device.
• Mid-upper arm circumference — About 5 minutes.
  Mid-upper arm circumference (measured in centimeters) will be obtained using a flexible tape measure following standardized protocols.
• Grip strength — About 5 minutes.
  Grip strength will be obtained using a dynamometer(CAMRY, EH101).
• Skin carotenoid concentration — About 5 minutes.
  Skin carotenoid concentration will be measured in using the Veggie Meter，and the results will be expressed as Standard Point Score (SPS), typically ranging from 0 to 800 SPS. Higher SPS values indicate higher skin carotenoid concentration.
• Red Blood Cell Count — About 10 minutes.
  Red blood cell count will be measured in fasting blood samples.
• White Blood Cell Count — About 10 minutes.
  White blood cell count will be measured in fasting blood samples.
• Hemoglobin — About 10 minutes.
  Hemoglobin concentration will be measured in fasting blood samples, reported in grams per liter (g/L).
• Total Cholesterol — About 10 minutes.
  Total cholesterol concentration will be measured in fasting blood samples, reported in millimoles per liter (mmol/L).
• Triglycerides — About 10 minutes.
  Triglycerides concentration will be measured in fasting blood samples, reported in millimoles per liter (mmol/L).
• High-Density Lipoprotein Cholesterol — About 10 minutes.
  High-density lipoprotein cholesterol (HDL-C) concentration will be measured in fasting blood samples, reported in millimoles per liter (mmol/L).
• Low-Density Lipoprotein Cholesterol — About 10 minutes.
  Low-density lipoprotein cholesterol (LDL-C) concentration will be measured in fasting blood samples, reported in millimoles per liter (mmol/L).
• Alanine Aminotransferase — About 10 minutes.
  Alanine aminotransferase (ALT) activity will be measured in fasting blood samples, reported in units per liter (U/L).
• Aspartate Aminotransferase — About 10 minutes.
  Aspartate aminotransferase (AST) activity will be measured in fasting blood samples, reported in units per liter (U/L).
• Total Bilirubin — About 10 minutes.
  Total bilirubin concentration will be measured in fasting blood samples, reported in micromoles per liter (μmol/L).
• Direct Bilirubin — About 10 minutes.
  Direct bilirubin concentration will be measured in fasting blood samples, reported in micromoles per liter (μmol/L).
• Indirect Bilirubin — About 10 minutes.
  Indirect bilirubin concentration will be measured in fasting blood samples, reported in micromoles per liter (μmol/L).
• Blood Urea Nitrogen — About 10 minutes.
  Blood urea nitrogen (BUN) concentration will be measured in fasting blood samples, reported in millimoles per liter (mmol/L).
• Serum Uric Acid — About 10 minutes.
  Serum uric acid concentration will be measured in fasting blood samples, reported in micromoles per liter (μmol/L).
• Serum Creatinine — About 10 minutes.
  Serum creatinine concentration will be measured in fasting blood samples, reported in micromoles per liter (μmol/L).
• Vitamin D levels — About 10 minutes.
  Vitamin D levels will be obtained by collecting blood samples.
• Gut microbiota — About 10 minutes.
  Gut microbiota will be obtained by collecting fecal samples.
• Secondary sexual characteristics — About 5 minutes.
  The Tanner stages are used to assess the development of secondary sexual characteristics and are divided into five stages. For boys, the evaluation includes pubic hair development and genital development (including testicular and penile growth). For girls, the evaluation includes pubic hair development and breast development (thelarche).
• Basal metabolic rate — About 30 minutes.
  The basal metabolic rate in kcal or MJ will be measured by respiratory indirect calorimetry (Cosmed).
• Total energy expenditure — About 14 days.
  Total energy expenditure in kcal or MJ will be measured using the DLW method. TEE will then be calculated using mean CO2 production using the Weir equation.
• Environmental temperature — About 14 days.
  The iButton (DS1921G) monitors will be provided for the assessment of both indoor and outdoor temperature of their living environment, measured in degrees Celsius (°C).
• Physical activity energy expenditure — About 14 days.
  Physical activity energy expenditure will be recorded using a GT3X accelerometer worn at the waist for a consecutive period of 14 days, with results expressed in kilocalories (kcal) or megajoules (MJ) per day.
• Total moderate-to-vigorous physical activity (MVPA) — About 14 days.
  Total MVPA will be recorded using a GT3X accelerometer worn at the waist for a consecutive period of 14 days, with results expressed in minutes per day (min/day).
• Vector magnitude counts — About 14 days.
  Vector magnitude counts will be recorded using a GT3X accelerometer worn at the waist for a consecutive period of 14 days, with results expressed as counts per minute (cpm). Higher cpm values indicate greater overall physical activity intensity, reflecting the average level of movement during the monitoring period.

Trial sites (7)

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