Influence of Food Texture on Appetite Control, Gastric Emptying, and Energy Expenditure

The aim of the study is to investigate the effect of liquid versus semi-solid meals on the regulation of energy balance in healthy young adults.The main questions it aims to answer are:

• Does a protein-rich liquid meal result in less satiety and therefore higher ad libitum energy intake at the next meal than an isocaloric oatmeal with the same macronutrient ratio?
• Is the consumption of a protein-rich liquid meal as a beverage in addition to an ad libitum oatmeal less compensated within the meal and at the next meal and provides thus a higher ad libitum energy intake than an isovolumetric noncaloric soft drink in addition to an ad libitum oatmeal?

Researchers will compare a protein-rich liquid meal to an isocaloric oatmeal with matched macronutrient composition to answer the first question. Researchers will compare a protein-rich liquid meal + oatmeal to a noncaloric softdrink (water with sucralose and flavoring) + oatmeal to answer the second question.

Participants will:

• spend 4 intervention days in a metabolic chamber (whole room indirect calorimeter)
• consume pre-definied preloads for breakfast and ad libitum lunch meals on 4 intervention days

Study Overview

• Status: Completed
• Conditions: Nutrition; Healthy Male and Female Subjects
• Intervention / Treatment: Other: liquid meal; Other: semi-solid meal; Other: caloric drink + semi-solid meal; Other: non-caloric drink + semi-solid meal

• Study Type: Interventional
• Enrollment (Actual): 20
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Germany
  • Kiel, Germany
    • Kiel University, Institute of Human Nutrition

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• healthy males and females
• Body Mass Index between 19-35 kg/m2
• low to medium habitual physical activity
• women with regular menstrual cycle (during intervention in follicular phase)

Exclusion Criteria:

• smoking (cigarettes + cannabis)
• chronic illnesses
• regular intake of medication
• Anemia and/or iron deficiency
• food allergies / intolerances
• vegans
• regular high physical activity (exercise >1 hour/d)
• current weight loss diet / weight loss of >5 kg in the last 3 months
• restraint eaters (according to the German version of the 'Three-Factor-Eating-Questionnaire', Stunkard und Messick (1985))
• active participation in another trial
• pregnant / lactating women
• persons incapable of giving informed legal consent

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: isocaloric preload; In this arm of the study, participants receive two different isocaloric preloads for breakfast, one as a liquid meal and one as oatmeal.	Other: liquid meal; An isocaloric amount (500 kcal) of a commercially available liquid meal with a matched macronutrient composition is consumed. After 5 hours, lunch is eaten ad libitum.; Other: semi-solid meal; An isocaloric amount (500 kcal) of a commercially available semi-solid oatmeal with a matched macronutrient composition is consumed. After 5 hours, lunch is eaten ad libitum.
Experimental: ad libitum preload; In this arm of the study, participants are given two different isovolumetric drinks as a preload in addition to an ad libitum oatmeal breakfast. One drink is a liquid meal, the other is a non-caloric soft drink (water, sucralose, flavour).	Other: caloric drink + semi-solid meal; A predefined amount of a caloric drink (= liquid meal) together with an ad libitum amount of a semi-solid meal is consumed. After 5 hours, lunch is eaten ad libitum.; Other: non-caloric drink + semi-solid meal; A predefined amount of a non-caloric drink (= water, sucralose, flavor) together with an ad libitum amount of a semi-solid meal is consumed. After 5 hours, lunch is eaten ad libitum.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
ad libitum energy intake	measured during preload and lunch [kcal] following the preload in both arms	for 9 hours after the consumption of the preloads

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
gastric emptying	gastric half-emptying time [min] determined with 13C-sodium acetate breath test, only assessed during arm "isocaloric preload"	for 4 hours after the consumption of the isocaloric preloads
eating rate at lunch	assessed during ad libitum lunch [g/min] following the preload in both arms	at 5 hours after consumption of the preload
number of chews per bite at lunch	assessed during ad libitum lunch [number] following the preload in both arms	at 5 hours after consumption of the preload
serum ghrelin concentrations	area under the serum ghrelin concentration curve over 3 hours	for 3 hours after consumption of the isocaloric preloads
serum peptide-YY (PYY) concentrations	area under the serum PYY concentration curve over 3 hours	for 3 hours after consumption of the isocaloric preloads
serum Glucagon-like Peptide 1 (GLP-1) concentrations	area under the serum GLP-1 concentration curve over 3 hours	for 3 hours after consumption of the isocaloric preloads
energy expenditure	Measured as kcal for 9.5 hours in a whole room indirect calorimeter (WRIC), including the consumption of the preload and the ad libitum lunch.	measured for 9.5 hours
macronutrient oxidation	Measured as respiratory exchange ratio (RER) for 9.5 hours in a whole room indirect calorimeter (WRIC), including the consumption of the preload and the ad libitum lunch.	measured for 9.5 hours

Collaborators and Investigators

• Sponsor: University of Kiel
• Investigators: Principal Investigator: Anja Bosy-Westphal, PhD, MD, University of Kiel, Department of Human Nutrition

Study record dates

Study Major Dates

• Study Start (Actual): April 1, 2025
• Primary Completion (Actual): December 31, 2025
• Study Completion (Actual): March 31, 2026

Study Registration Dates

• First Submitted: February 13, 2025
• First Submitted That Met QC Criteria: February 24, 2025
• First Posted (Actual): February 28, 2025

Study Record Updates

• Last Update Posted (Actual): May 5, 2026
• Last Update Submitted That Met QC Criteria: April 28, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: gastric emptying; appetite control; food texture; energy balance; ad libitum energy intake; whole room indirect calorimetry (WRIC); liquid meals
• Other Study ID Numbers: ABW-2025-YF

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Due to the privacy statement in the subject information form, data may not be publicly available but might be available upon reasonable request.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No