Inter-Individual Variability in Early Diet-Induced Thermogenesis After a Standardized Meal

Inter-Individual Variability in Early Postprandial Thermogenesis Following a Standardized Liquid Meal

This study aims to characterize how individuals differ in their metabolic response to food intake, specifically focusing on early diet-induced thermogenesis (DIT). DIT refers to the increase in energy expenditure that occurs after eating and reflects the body's metabolic response to processing nutrients.

Healthy adult participants will complete a single laboratory visit under standardized conditions. Resting metabolic rate will first be measured, followed by consumption of a standardized liquid meal (550 kcal). Energy expenditure will then be continuously monitored for 3 hours using indirect calorimetry.

The primary objective is to quantify inter-individual variability in early postprandial thermogenesis. Rather than estimating total daily energy expenditure, this study focuses on the early metabolic response following meal ingestion. Findings will improve understanding of differences in metabolic efficiency between individuals and support future research in metabolism and personalized nutrition.

Study Overview

• Status: Not yet recruiting
• Conditions: Diet-induced Thermogenesis
• Intervention / Treatment: Other: Standardized Liquid Meal

Detailed Description

Diet-induced thermogenesis (DIT) represents the increase in energy expenditure above resting levels following food intake and reflects the energetic costs of digestion, absorption, transport, and metabolism of nutrients. Although DIT typically accounts for a relatively small proportion of total daily energy expenditure, it plays an important role in postprandial metabolism and may contribute to inter-individual differences in energy balance and body weight regulation.

Most prior research has focused on estimating total DIT over prolonged postprandial periods (e.g., 4-6 hours or longer). However, these approaches may obscure meaningful variability in the early phase of the thermogenic response, which is characterized by rapid and dynamic metabolic changes. The most pronounced increase in energy expenditure typically occurs within the first 1-3 hours following meal ingestion, driven by early physiological processes including gastrointestinal activity and neuroendocrine responses.

Emerging evidence suggests that individuals vary substantially in their metabolic response to a standardized meal, even under controlled conditions. However, this variability is often averaged out in group-level analyses or diluted by long measurement windows. The present study is specifically designed to characterize observed inter-individual variability in early DIT, rather than to estimate total thermogenesis or test intervention effects.

This study is a controlled, cross-sectional physiological study in healthy adults. Each participant will complete a single study visit under standardized laboratory conditions. After an initial resting period, resting metabolic rate will be measured using indirect calorimetry. Participants will then consume a standardized liquid meal providing 550 kcal, after which energy expenditure will be continuously monitored for 180 minutes.

Strict pre-test standardization procedures (including fasting, avoidance of exercise, caffeine, and alcohol) will be implemented to minimize non-biological variability. Body composition will also be assessed to support interpretation of metabolic responses.

The primary outcome is early DIT, quantified as the increase in energy expenditure above baseline over the postprandial period. Secondary analyses will describe the distribution, magnitude, and temporal characteristics of the thermogenic response, including peak response and time to peak.

By focusing on the early postprandial phase, this study aims to provide detailed characterization of variability in metabolic responses under tightly controlled conditions. These findings will contribute to a better understanding of human metabolic heterogeneity and may inform future research in metabolic physiology, obesity, and personalized nutrition.

Although a standardized liquid meal is administered as part of the protocol, the study is designed to characterize physiological variability in metabolic response rather than to evaluate the effect of an intervention.

• Study Type: Interventional
• Enrollment (Estimated): 30
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Yftach Prof. Gepner; Phone Number: 0506828501; Email: gepner@tauex.tau.ac.il
• Study Contact Backup: Name: Lien Bruck; Phone Number: 0587487431; Email: lienbruck@tauex.tau.ac.il

Study Locations

• Israel
  • Tel Aviv, Israel, 6428607
    • Sylvan Adams Sport Science Institute

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Adults aged ≥18 years
• Stable body weight (±2 kg over the previous 3 months)
• Generally healthy individuals
• Ability to comply with study procedures, including fasting and remaining at rest - during measurements

Exclusion Criteria:

• Use of medications known to affect metabolism (e.g., GLP-1 receptor agonists, systemic corticosteroids, uncontrolled thyroid disease)
• Insulin-treated diabetes
• Pregnancy or lactation
• Acute illness at the time of testing
• Inability to comply with pre-test requirements (e.g., fasting, avoiding caffeine, alcohol, or physical activity)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Healthy Adult Participants; Healthy adults (≥18 years) participating in a single laboratory visit. All participants undergo resting metabolic rate assessment, consume a standardized liquid meal (550 kcal), and complete continuous postprandial energy expenditure measurement using indirect calorimetry under controlled conditions.	Other: Standardized Liquid Meal; Consumption of a standardized liquid meal (~550 kcal) under controlled laboratory conditions, followed by continuous measurement of energy expenditure using indirect calorimetry for assessment of postprandial thermogenesis. The procedure is used for measurement purposes only and is not intended as a therapeutic intervention.; Other Names: Ensure®

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Early Diet-Induced Thermogenesis Area Under the Curve	Area under the curve for diet-induced thermogenesis over 180 minutes after consumption of the standardized liquid meal. DIT will be calculated as postprandial energy expenditure minus baseline resting energy expenditure and expressed as kcal/180 min.	From meal completion to 180 minutes post-meal

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mean Diet-Induced Thermogenesis	Mean increase in energy expenditure above baseline resting energy expenditure during the 180-minute postprandial measurement period, expressed as kcal/min or kcal/180 min.	From meal completion to 180 minutes post-meal
Peak Diet-Induced Thermogenesis	Maximum increase in energy expenditure above baseline resting energy expenditure observed during the 180-minute postprandial measurement period, expressed as kcal/min.	From meal completion to 180 minutes post-meal
Time to Peak Diet-Induced Thermogenesis	From meal completion to 180 minutes post-meal	Time from completion of the standardized liquid meal to the maximum observed increase in energy expenditure, expressed in minutes.
Percent Increase in Energy Expenditure Above Baseline	Percentage increase in postprandial energy expenditure above baseline resting energy expenditure during the 180-minute measurement period.	From meal completion to 180 minutes post-meal
Fat-Free Mass-Normalized Diet-Induced Thermogenesis	Diet-induced thermogenesis area under the curve normalized to fat-free mass, expressed as kcal/180 min/kg fat-free mass.	From meal completion to 180 minutes post-meal

Collaborators and Investigators

• Sponsor: Tel Aviv University

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): June 1, 2027
• Study Completion (Estimated): June 1, 2027

Study Registration Dates

• First Submitted: May 13, 2026
• First Submitted That Met QC Criteria: May 27, 2026
• First Posted (Actual): May 28, 2026

Study Record Updates

• Last Update Posted (Actual): May 28, 2026
• Last Update Submitted That Met QC Criteria: May 27, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Energy expenditure; Indirect calorimetry; Diet-induced thermogenesis; Postprandial metabolism; Metabolic variability; Standardized meal
• Other Study ID Numbers: 0012144-1

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No