NCT07429058

Metabolic Flexibility and Ketone Production During Energy Deficit

Indices of Metabolic Flexibility and Ketone Production During Short-Term Energy Deficit With and Without Dietary Carbohydrate Restriction

• Status: Completed
• Phase: N/A
• Study type: Interventional
• Enrollment: 30 (actual)
• Sponsor: Technical University of Munich · Academic / Other
• Sex: All
• Age: 18 Years – 40 Years
• Healthy volunteers: Accepted

Summary

This randomized, interventional study examines the effects of short-term carbohydrate restriction, with and without caloric restriction, on indices of metabolic flexibility in healthy adults. Participants are randomly assigned to either a low-carbohydrate diet or a standard diet under energy balance, followed by the same diet under controlled caloric restriction. Primary outcomes include measures of carbon dioxide production, breath ketones and interstitial glucose. Secondary outcomes include blood and urinary ketones, body weight, body composition, and selected metabolic biomarkers.

Detailed description

This is a monocentric, randomized, open-label nutrition intervention conducted in healthy adults aged 18 to 40 years. The study investigates the effects of short-term carbohydrate and caloric restriction on indices of metabolic flexibility. After screening and baseline assessments, participants undergo an initial period of energy balance with a standardized diet, followed by a 2-week intervention phase. Participants are randomly assigned in a 1:1 ratio to either a low-carbohydrate diet or a standard mixed diet. Participants are instructed to maintain their habitual physical activity throughout the study. During the first week of the intervention period, energy intake is equivalent to estimated energy requirements. During the second week, energy intake is reduced by \~500 kcal/d. Metabolic outcomes are assessed using repeated laboratory and remote measurements. Primary outcomes include breath-based measures of carbon dioxide and acetone production, as well as continuous glucose monitoring. Secondary outcomes include urinary and capillary blood ketones, body weight, body composition, resting metabolic rate, plasma glucose and selected biomarkers (leptin, insulin, triiodothyronine, GLP-1, HbA1c). Data are collected at baseline, during the intervention, and post-intervention. The total participation time per participant is approximately three weeks. The study aims to characterize short-term metabolic responses to dietary carbohydrate manipulation and energy deficit under controlled conditions.

Conditions

• Dietary Carbohydrate Restriction, Energy Deficit

Interventions

Type	Name	Description
OTHER	Low-Carbohydrate Diet	Participants receive a low-carbohydrate diet. All meals are provided and individually tailored based on estimated energy requirements. Carbohydrate intake is restricted to 75-125 g per day, with the remaining energy intake derived from fat and protein. The intervention is administered for 14 days.
OTHER	Standard Diet With Caloric Restriction	Participants receive a standard mixed diet. All meals are provided and individually tailored based on estimated energy requirements. The macronutrient distribution consists of approximately 50-55% carbohydrates, 25-35% fat, and 15% protein. The intervention is administered for 14 days.

Timeline

• Start date: 2023-11-24
• Primary completion: 2024-03-11
• Completion: 2024-04-26
• First posted: 2026-02-24
• Last updated: 2026-02-24

Locations

1 site across 1 country: Germany