Ketogenic Diets for Weight Loss Maintenance: Impact on Energy Expenditure and Appetite in Individuals With Obesity

Not Applicable

Recruiting

• Conditions: Obesity

• Registration Number: NCT06736028
• Lead Sponsor: University of Alabama at Birmingham

Brief Summary

The goal of this clinical trial is to investigate whether a Ketogenic Diet (KD) can increase Total Energy Expenditure (TEE), while benefiting appetite, during weight loss maintenance in reduced-obese individuals.

Detailed Description

The total duration of the intervention will be 10 weeks. Participants will first undergo 4 weeks of a low-energy diet (LED), aiming to induce a minimum of 5% weight loss (weight loss phase). Those who achieve at least a 5% weight loss will then be randomized (1:1) to a 6-week weight loss maintenance (WLM) diet, either a KD or an isocaloric low-fat diet, with the first 2 weeks being a gradual refeeding.

Study Timeline

• Study First Submitted: 2024-12-10
• Study First Submitted QC: 2024-12-13
• Study First Posted: 2024-12-16
• Status Verified: 2025-07
• Last Update Submitted: 2025-07-10
• Last Update Posted: 2025-07-15
• Study Start: 2025-08-01
• Primary Completion: 2025-12-31
• Study Completion: 2026-03-31

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 20

Inclusion Criteria

• BMI 30-45 kg/m2
• Both men and women
• Age between 18-65 years
• Sedentary to moderately active (<2 h/wk of moderate, structured, intentional, exercise)

Exclusion Criteria

• Pregnancy or lactation
• Daily use of tobacco (>1 pk/wk)
• Change in weight greater than 5 lb in the previous 3 months
• Cognitive impairment
• Previous bariatric surgery
• History of eating disorder
• Presence of any condition (e.g. DM2, PCOS, inflammatory disease, untreated thyroid disease, fluid overload states such as chronic kidney disease, congestive heart failure, or cirrhosis)
• Use of any medication (e.g., glucocorticoid, GLP-1 analogues, hormone replacement therapy) deemed to interfere with study outcomes.
• Pre-menopausal women will need to have a regular menstrual cycle (28+/-2 days) or be on hormonal contraceptives
• Fasting glucose plasma concentration >125 mg/dl and/or HbA1c > 6.4%

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Primary Outcome Measures

Name	Time	Method
Change from baseline total energy expenditure	Baseline, week 6, week 10	Total Energy Expenditure (TEE) refers to the total amount of energy (calories) your body uses in a day. Twenty-four-hour EE and RQ will be measured inside the whole room indirect calorimeter (chamber) following standard procedures

Secondary Outcome Measures

Name	Time	Method
Change in appetite ratings	Baseline, week 6, week 10	Subjective appetite ratings are personal feelings or perceptions about hunger, fullness, desire to eat (DTE), and prospective food consumption (PFC) usually measured using self-reported scales ranging from "not at all" to "extremely". Subjective appetite ratings (hunger, fullness, DTE and PFC) will be measured using a validated 10cm visual analog scale which will be given to the participants inside the chamber before meals.
Change in total body composition	Baseline, week 4, week 6, week10	FM, bone mass, and lean body mass will be determined by dual-energy X-ray absorptiometry (iDXA instrument, GE Healthcare Lunar, Madison, WI) with the use of software version 1.5g (Lunar Corp).
Change in fasting insulin	Baseline, week 6, week 10	Circulating (serum) fasting insulin will be measured using validated methods
Change in fasting cholecystokinin	Baseline, week 6, week 10	Circulating (plasma) fasting cholecystokinin will be measured by RIA.
Change in fasting ghrelin	Baseline, week 6, week 10	Circulating (plasma) fasting ghrelin concentrations will be measured by ELISA
Change in fasting glucagon-like peptide-1	Baseline, week 6, week 10	Circulating (plasma) fasting total GLP-1 will be measured by ELISA
Change in fasting peptide YY (PYY)	Baseline, week 6, week 10	Circulating (plasma) fasting PYY3-36 concentrations will be measured by ELISA
Change in total body weight	Baseline, week 4, week 6, week 10	Body weight is the total amount a person weighs when measured on a scale.
Change in mechanical efficiency	Baseline, week 6, week 10	Walking economy will be assessed using a submaximal treadmill test, performed 90 minutes after breakfast. Following a familiarization period, participant will walk on the treadmill at 2 miles/hour for 15 minutes, followed by another 15 minutes at 2.5 miles/hour.
Change in resting energy expenditure	Baseline, week 6, week 10	Resting Energy Expenditure (REE) is the amount of energy (calories) your body needs to keep working while you're at rest. Participants will enter the chamber in the morning in the fasting state. REE will be measured while the participant is in the metabolic chamber.
Change in postprandial insulin	Baseline, week 6, week 10	Circulating (serum) insulin measured before and 30, 60, 90, and 120 minutes after intake of breakfast with validated methods
Change in postprandial cholecystokinin	Baseline, week 6, week 10	Circulating (plasma) cholecystokinin measured before and 30, 60, 90, and 120 minutes after intake of breakfast with RIA.
Change in postprandial ghrelin	Baseline, week 6, week 10	Circulating (plasma) ghrelin measured before and 30, 60, 90, and 120 minutes after intake of breakfast with ELISA
Change in postprandial glucagon-like peptide-1	Baseline, week 6, week 10	Circulating (plasma) total GLP-1 measured before and 30, 60, 90, and 120 minutes after intake of breakfast by ELISA
Change in postprandial peptide yy	Baseline, week 6, week 10	Circulating (plasma) PYY3-36 concentrations measured before and 30, 60, 90, and 120 minutes after intake of breakfast with ELISA

Trial Locations

Locations (1)

University of Alabama at Birmingham; 🇺🇸 Birmingham, Alabama, United States