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NCT Number: NCT06736028

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

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.

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Key information

Conditions

Obesity Body Weight Body Weight Changes Nutrition Disorders Nutritional and Metabolic Diseases Overnutrition Overweight Pathological Conditions, Signs and Symptoms Signs and Symptoms Weight Loss

Age range

18 year–65 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

University of Alabama at Birmingham

Birmingham, Alabama, 35294, United States

Location status: Recruiting

Location contact

Catia Martins, PhD

CONTACT

[email protected]

2059347922

About this study

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.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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%

Treatment and study plan

diet therapy

Behavioral

Participants will be provided food to meet the ketogenic diet prescription for the 6-week weight maintenance phase.

Calorie Restriction

Behavioral

Participants will follow a commercial low-energy diet and be provided with meal replacements for 4 weeks aiming to achieve a minimum of 5% weight loss.

Behavioral support

Behavioral

Participants will meet weekly with a registered dietitian, for a 20-minute consultation throughout the entire study period (10 weeks) to increase engagement and improve adherence and retention.

Primary outcomes

  1. Change from baseline total energy expenditure

    Time frame: 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 outcomes

  1. Change in appetite ratings

    Time frame: 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.

  2. Change in total body composition

    Time frame: Baseline, week 4, week 6, week 10

    Bioimpedance analysis (BIA) will be used to measure fat mass, fat-free mass, total, extra, and intra-cellular water.

  3. Change in total body composition

    Time frame: 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).

  4. Change in fasting insulin

    Time frame: Baseline, week 6, week 10

    Circulating (serum) fasting insulin will be measured using validated methods

  5. Change in fasting cholecystokinin

    Time frame: Baseline, week 6, week 10

    Circulating (plasma) fasting cholecystokinin will be measured by RIA.

  6. Change in fasting ghrelin

    Time frame: Baseline, week 6, week 10

    Circulating (plasma) fasting ghrelin concentrations will be measured by ELISA

  7. Change in fasting glucagon-like peptide-1

    Time frame: Baseline, week 6, week 10

    Circulating (plasma) fasting total GLP-1 will be measured by ELISA

  8. Change in fasting peptide YY (PYY)

    Time frame: Baseline, week 6, week 10

    Circulating (plasma) fasting PYY3-36 concentrations will be measured by ELISA

  9. Change in total body weight

    Time frame: Baseline, week 4, week 6, week 10

    Body weight is the total amount a person weighs when measured on a scale.

  10. Change in mechanical efficiency

    Time frame: 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.

  11. Change in resting energy expenditure

    Time frame: 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.

  12. Change in postprandial insulin

    Time frame: Baseline, week 6, week 10

    Circulating (serum) insulin measured before and 30, 60, 90, and 120 minutes after intake of breakfast with validated methods

  13. Change in postprandial cholecystokinin

    Time frame: Baseline, week 6, week 10

    Circulating (plasma) cholecystokinin measured before and 30, 60, 90, and 120 minutes after intake of breakfast with RIA.

  14. Change in postprandial ghrelin

    Time frame: Baseline, week 6, week 10

    Circulating (plasma) ghrelin measured before and 30, 60, 90, and 120 minutes after intake of breakfast with ELISA

  15. Change in postprandial glucagon-like peptide-1

    Time frame: 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

  16. Change in postprandial peptide yy

    Time frame: 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

Other outcomes

  1. Blood work: beta hydroxybutyrate

    Time frame: Week 1, week 2, week 3, week 4, week 5, week 6, week 7, week 8, week 9, week 10

    Adherence to the dietary interventions will be assessed using objective biochemical analysis through the measurement of beta hydroxybutyrate in blood using a ketone meter.

  2. Urine sample: acetoacetate

    Time frame: Week 1, week 2, week 3, week 4, week 5, week 6, week 7, week 8, week 9, week 10

    Adherence to the dietary interventions will be assessed using objective biochemical analysis through the measurement of acetoacetate in urine using Ketostix reagent strips.

  3. Change in glucose

    Time frame: Baseline, week 6, week 10

    The fasting blood sample collected before the participants enter the chamber will be analyzed for circulating glucose using the SIRRUS analyzer.

  4. Change in total cholesterol

    Time frame: Baseline, week 6, week 10

    The fasting blood sample collected before the participants enter the chamber will be analyzed for circulating total cholesterol concentrations using the SIRRUS analyzer.

  5. Change in high-density lipoprotein cholesterol

    Time frame: Baseline, week 6, week 10

    The fasting blood sample collected before the participants enter the chamber will be analyzed for circulating HDL-C using the SIRRUS analyzer.

  6. Change in triglycerides

    Time frame: Baseline, week 6, week 10

    The fasting blood sample collected before the participants enter the chamber will be analyzed for circulating triglyceride concentrations using the SIRRUS analyzer.

  7. Change in free fatty acids

    Time frame: Baseline, week 6, week 10

    The fasting blood sample collected before the participants enter the chamber will be analyzed for circulating free fatty acid concentrations using the SIRRUS analyzer.

  8. Change in average appetite

    Time frame: Baseline, week 1, week 2, week 3, week 4, week 5, week 6, week 7, week 8, week 9, week 10

    Participants will be asked to report their average hunger, fullness, desire to eat and prospective food consumption (e.g. how hungry did you feel this week? how much did you think about food this week?) over the previous week using a 10-cm visual analogue scale ranging from "not at all" to "extremely".

Study contacts

Contact information is provided by the study sponsor or research team.

Catia Martins, PhD

CONTACT

[email protected]

205-934-7922

Sponsors and collaborators

Lead sponsor

University of Alabama at Birmingham

Other

Collaborators

  • National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Registry information

Acronym: KETOWEI

Important dates

Study start
2025
Primary completion
2026
Study completion
2027
First posted
Dec 16, 2024
Registry last updated
Apr 7, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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