An observational study in Obesity and Overweight, sponsored by University Hospital Schleswig-Holstein. Completed at 1 site in Germany. Open to participants aged 18 Years to 70 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-07-07.
Sponsored by University Hospital Schleswig-Holstein · Observational
This study examines why some individuals with obesity have difficulty losing weight, whereas some lean individuals struggle to gain weight. The investigators will measure how the human body uses energy during a fasting period and after consumption of a specially designed, low-protein meal. By comparing these responses, the investigators aim to identify different "metabolic phenotypes" that affect weight control. Findings from this research may lead to more personalized treatments for managing weight. Participation in this study involves simple tests and basic body measurements.
This study aims to better understand why certain individuals find it difficult to lose weight while others struggle to gain weight. Investigators believe that differences in how the human body uses energy-referred to as the metabolic phenotype-may play a key role.
Two groups of participants will be compared: one group includes lean individuals who have difficulty gaining weight, and the other group consists of individuals with obesity who have difficulty losing weight. Participants will undergo a series of tests designed to measure how the human body burns calories under different conditions.
The study involves two main components:
A technique called indirect calorimetry will record oxygen consumption and carbon dioxide production. These measurements help calculate resting energy expenditure (REE), which refers to the calories the body burns while at rest, and any changes that occur after fasting and eating.
The goal is to identify distinct metabolic patterns. Some individuals may have a "thrifty" metabolism that conserves energy, making weight loss more challenging, whereas others may have a "spendthrift" metabolism that expends more energy, potentially explaining difficulty in gaining weight. Understanding these differences could lead to more personalized and effective weight management strategies.
This study is conducted under strict safety and ethical standards to ensure minimal risk to participants. By examining the relationship between metabolism and weight control, the findings may pave the way for improved treatments for obesity and related weight issues.
11,522 studies on the registry are indexed under Obesity; 2,033 are open to participants now.
This study's enrollment of 20 is below the median of 114 across 2,154 observational studies indexed under Obesity.
Browse Obesity studies →University Hospital Schleswig-Holstein is the lead sponsor of 163 studies on the registry; 25 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Participants will be recruited from the general adult population, focusing on two specific groups:
All participants must be generally healthy, between 18 and 70 years old, and report a stable body weight (less than 5% fluctuation) in the last six months. Recruitment will occur via community outreach, advertisements, and existing volunteer registries. Potential participants with conditions or circumstances that could affect appetite, energy expenditure, or study compliance will be excluded.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
A blood test of average blood sugar over the past two to three months, given as a percentage or in mmol/mol. 6.5% (48 mmol/mol) or more is the usual threshold for diabetes, normally confirmed by a second test.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HbA1c
A blood test of average blood sugar over the past two to three months, given as a percentage or in mmol/mol. 6.5% (48 mmol/mol) or more is the usual threshold for diabetes, normally confirmed by a second test.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants in this group are lean individuals (BMI 18.5-22.0 kg/m²) who have difficulty gaining weight. They will undergo a 24-hour fasting period followed by a controlled low-protein, high-calorie meal test. Researchers will measure their resting metabolic rate before and after fasting, as well as the body's response to the test meal. By comparing these results to those of other groups, the study aims to identify metabolic factors that influence weight gain difficulties and guide future personalized treatments.
Participants in this group are individuals with obesity (BMI \>30 kg/m²) who have difficulty losing weight. They will undergo a 24-hour fasting period followed by a controlled low-protein, high-calorie meal test. Researchers will measure their resting metabolic rate before and after fasting, as well as the body's response to the test meal. By comparing these findings with those of other groups, the study seeks to uncover metabolic factors that contribute to weight loss difficulties and guide more personalized treatment approaches.
Identification of Metabolic Phenotypes in Lean vs. Obese Individuals
We aim to determine whether individuals with obesity (BMI \>30 kg/m²) exhibit a more "thrifty" metabolic phenotype (lower resting metabolic rate \[RMR\] after 24-hour fasting and reduced diet-induced thermogenesis \[DIT\]) compared to lean individuals (BMI 18.5-22 kg/m²) who have trouble gaining weight, hypothesized to show a more "spendthrift" metabolic phenotype (increased RMR after fasting and higher DIT). RMR is measured via indirect calorimetry before and after a 24-hour fast, followed by a high-calorie, low-protein meal test to assess DIT.
Time frame: Measured at baseline (Day 1) and after 24-hour fasting (Day 2)
Correlation Between Fasting-Induced Energy Expenditure Changes and Diet-Induced Thermogenesis
Evaluate how the change in resting metabolic rate (RMR) after a 24-hour fast relates to diet-induced thermogenesis (DIT) following a high-calorie, low-protein meal. This will clarify the interaction between fasting adaptation and meal-related energy expenditure in lean vs. obese individuals.
Time frame: Baseline (Day 1), post-fasting (Day 2), and after the meal test (Day 2)
Assessment of Metabolic Flexibility via Respiratory Quotient
Determine whether individuals with obesity show a smaller shift in their respiratory quotient (RQ) after fasting and the meal test, indicating lower metabolic flexibility compared to lean participants.
Time frame: Baseline (Day 1), post-fasting (Day 2), and after the meal test (Day 2)
Correlation Between Weight Gain at 12-Month Follow-Up and Initial Metabolic Phenotype
Body weight (in kilograms) will be measured at baseline and again after 12 months using a calibrated scale. The correlation between weight change over this period and the initial metabolic phenotype (classified as "thrifty" or "spendthrift") will be assessed. The metabolic phenotype is determined by changes in resting metabolic rate (RMR) and diet-induced thermogenesis (DIT), both measured via indirect calorimetry.
Time frame: 12-month follow-up
Correlation Between Weight Gain at 12-Month Follow-Up and Diet-Induced Thermogenesis
Body weight (in kilograms) will be measured at baseline and again after 12 months using a calibrated scale. The correlation between weight change over this period and the magnitude of diet-induced thermogenesis (DIT) will be assessed. DIT is determined via indirect calorimetry after a controlled, low-protein meal. This assessment will help identify whether higher or lower DIT predicts long-term weight change.
Time frame: 12-month follow-up
Correlation Between Meal Test Diet-Induced Thermogenesis and Fibroblast Growth Factor 21 (FGF-21) Secretion
Fibroblast Growth Factor 21 (FGF-21) levels (in picograms per milliliter) will be measured in blood samples collected after the high-calorie, low-protein meal. The correlation between FGF-21 levels and diet-induced thermogenesis (DIT) will be assessed. DIT is measured using indirect calorimetry to quantify energy expenditure following the meal. This analysis will help determine whether FGF-21 may serve as a biomarker of metabolic adaptation.
Time frame: After the meal test (Day 2)
Correlation Between Gut Hormones and Changes in Energy Expenditure
Serum levels of gut hormones (e.g., ghrelin, glucagon-like peptide-1 \[GLP-1\]) will be measured in picograms per milliliter. Resting metabolic rate (RMR) and diet-induced thermogenesis (DIT) will be assessed via indirect calorimetry before and after a 24-hour fast, as well as after a high-calorie, low-protein meal. The correlation between gut hormone levels and changes in energy expenditure (RMR and DIT) will be evaluated to investigate hormonal influences on metabolic responses.
Time frame: Baseline (Day 1), after 24-hour fast (Day 2), and after the meal test (Day 2)
Plan to share: Undecided
Ran from Sep 2024 to primary completion in Mar 2026, 17 months.
Of 791 non-industry observational studies under Obesity, half reached primary completion within 40 months of starting (the median), counting those still running; a quarter within 17 and three quarters within 106. This study's 17 months is below that.
Counting every sponsor, half of 836 studies reached it within 39 months; a quarter within 17 and three quarters within 96.
How these figures are worked out, and which studies are left out of them.
This study is completed, as verified in Jul 2026. You cannot join it, but the record below documents what was studied.
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