High-Intensity Interval Training in Low Versus Normal Oxygen: Effects on Body Fat and Gut Health in Adults Aged 50-75 With Overweight or Obesity (HYPOXFAT)

NCT07796971 | Recruiting DMC

• 1 other identifier: ID-RCB : 2025-A01744-45
• Study Type: interventional
• Target: 32
• Locations: 1 country
• Sites: 1

Brief Summary

Overweight and obesity are major public health challenges worldwide, and their prevalence increases with age, partly because of age-related metabolic and hormonal changes. Beyond total fat mass, abdominal and particularly visceral fat accumulation is strongly associated with chronic low-grade inflammation, insulin resistance, hypertension and cardiovascular disease. Men are more likely to display an android fat distribution, while premenopausal women generally show a more protective gynoid distribution. However, declining sex hormone concentrations after menopause promote abdominal and visceral fat accumulation, increasing cardiometabolic risk. Physical activity is a cornerstone of overweight and obesity management. High-intensity interval training (HIIT) is an effective strategy for reducing total, abdominal and visceral fat and may produce greater benefits than moderate-intensity continuous training. Since 2016, our team has conducted several studies and reviews showing that HIIT performed on a cycle ergometer or treadmill, alone or combined with resistance training, reduces total and abdominal fat mass in people with overweight or obesity, regardless of age, sex or hormonal status. HIIT can also be performed under real or simulated hypoxic conditions to enhance cardiovascular, respiratory, circulatory, haematological and skeletal muscle adaptations. The Live Low-Train High model allows participants to live under normoxic conditions while being exposed to hypoxia only during exercise. Hypoxic HIIT has proved feasible and safe in people with metabolic disorders or physical deconditioning, including at simulated altitudes of 4,000-5,000 m. However, only two studies have suggested that hypoxic HIIT may enhance fat mass loss in people with overweight or obesity. Neither specifically assessed abdominal or visceral fat, and neither focused on postmenopausal women. Several mechanisms may contribute to HIIT-induced fat loss, including increased catecholaminergic stimulation and lipid oxidation during recovery, excess post-exercise oxygen consumption and changes in appetite regulation. The gut microbiota may also contribute to the regulation of adipose tissue and cardiometabolic health. Physical activity can increase bacterial diversity and promote beneficial taxa, particularly short-chain fatty acid-producing bacteria. Our previous HIIT studies identified associations between changes in selected bacteria and reductions in total or abdominal fat mass. Hypoxic exposure may also alter gut microbiota composition and abundance, with effects depending on the severity and type of hypoxia. This study will assess the effects of a 3-month cycle-ergometer HIIT programme, performed three times per week under hypoxic versus normoxic conditions, in adults aged 50-75 years with overweight or obesity. The primary objective is to determine whether hypoxic HIIT produces a greater reduction in abdominal and visceral fat mass than the same training performed in normoxia. Secondary outcomes will include total and regional fat and lean mass; fasting glucose, insulin, HbA1c and HOMA-IR; total cholesterol, triglycerides, HDL-C, LDL-C, ApoB, ApoA1 and the ApoB/ApoA1 ratio; high-sensitivity C-reactive protein and fibrinogen; systolic and diastolic blood pressure; blood biophysical properties; and faecal microbiota richness, diversity and taxonomic composition. Lipid oxidation during prolonged moderate-intensity exercise, maximal oxygen uptake and maximal aerobic power will also be assessed before and after the intervention. We hypothesise that hypoxic training will enhance improvements in body composition, metabolic and cardiovascular risk factors, aerobic fitness and lipid oxidation compared with normoxic training. We further hypothesise that hypoxia will modify faecal microbiota composition and that changes in selected bacterial taxa will be associated with changes in body composition and cardiovascular risk markers. The ultimate aim is to improve the management of adults aged 50-75 years with overweight or obesity by developing an effective 3-month HIIT programme performed under controlled hypoxic conditions.

Conditions

Obesity & Overweight; Fat Mass

Keywords

HIIT; normobaric hypoxia; fat mass; health; overweight; obesity; exercise prescription

Outcome Measures

Primary Outcomes (1)

• Relative Change in Total Abdominal Fat Mass

  Total abdominal fat mass will be measured by dual-energy X-ray absorptiometry (DXA) at baseline and after the 12-week intervention. The relative change will be calculated as: (abdominal fat mass at 12 weeks - abdominal fat mass at baseline) / abdominal fat mass at baseline. More negative values indicate a greater reduction in abdominal fat mass. The change will be compared between the hypoxic and normoxic HIIT groups.

  Baseline and immediately after the 12-week intervention

Secondary Outcomes (14)

• Relative Change in Body Mass

  Baseline and after 12 weeks of intervention

• Relative Change in Visceral Abdominal Fat Mass

  Baseline and after 12 weeks of intervention

• Relative Change in Total Lean Mass

  Baseline and after 12 weeks of intervention

• Relative Change in Waist-to-Hip Ratio

  Baseline and after 12 weeks of intervention

• Relative Change in metabolic Plasma parameters (TG, HBA1C, glucose, insulin, HDL, LDL)

  Baseline and after 12 weeks of intervention

Study Arms (2)

Hypoxic HIIT (HIIT-H)

EXPERIMENTAL

Participants will complete a 12-week cycle-ergometer HIIT programme, with three sessions per week, under normobaric hypoxia (FiO₂: 15%; simulated altitude: 3,000 m).

Behavioral: Hypoxic High-Intensity Interval Training

Normoxic HIIT (HIIT-N)

ACTIVE COMPARATOR

Participants will complete the same 12-week cycle-ergometer HIIT programme, with three sessions per week, under normoxic conditions (FiO₂: 21%).

Behavioral: Normoxic High-Intensity Interval Training

Interventions

Normoxic High-Intensity Interval Training BEHAVIORAL

Participants will complete 36 cycle-ergometer HIIT sessions over 12 weeks (three sessions per week) under normoxic conditions (FiO₂: 21%). Each session will include a 5-minute warm-up followed by 60 repetitions of 8 seconds of acceleration at approximately 80-85 rpm and 12 seconds of deceleration at approximately 60 rpm. The 8-second efforts will be performed at 75-80% of maximal aerobic power.

Also known as: Normoxic HIIT, HIIT-N

Normoxic HIIT (HIIT-N)

Hypoxic High-Intensity Interval Training BEHAVIORAL

Participants will complete 36 cycle-ergometer HIIT sessions over 12 weeks (three sessions per week) under normobaric hypoxia (FiO₂: 15%; simulated altitude: 3,000 m). Each session will include a 5-minute warm-up followed by 60 repetitions of 8 seconds of acceleration at approximately 80-85 rpm and 12 seconds of deceleration at approximately 60 rpm. The 8-second efforts will be performed at 75-80% of maximal aerobic power.

Also known as: Hypoxic HIIT, HIIT-H

Hypoxic HIIT (HIIT-H)

Eligibility Criteria

• Age: 50 Years - 75 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Aged 50-75 years, inclusive Male or postmenopausal female, defined as no menstruation during the previous 12 months Body mass index between 25 and 35 kg/m², inclusive Non-smoker or smoking no more than two cigarettes per day Stable body weight for at least three months before study initiation, defined as a change of less than 4 kg Stable dietary habits and physical activity level for at least three months before study initiation Willing to maintain usual dietary habits and physical activity level throughout the study Able and willing to comply with the study protocol Able and willing to provide written informed consent Affiliated with a social security scheme Willing to be registered in the French National Register of Volunteers Participating in Biomedical Research

Sponsors & Collaborators

• CREPS Auvergne Rhône-Alpes (AURA): collaborator
• Laboratoire des Adaptations Métaboliques à l'Exercice en conditions Physiologiques et Pathologiques: lead

Study Sites (1)

CREPS Auvergne Rhône-Alpes / Vichy

Bellerive-sur-Allier, 03321, France

RECRUITING

MeSH Terms

Conditions

Obesity; Overweight

Condition Hierarchy (Ancestors)

Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms

Central Study Contacts

Nathalie BOISSEAU, Professor

CONTACT

+33684331693; nathalie.boisseau@uca.fr

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Model Details: A randomised, controlled, single-centre, parallel-group study comparing 12 weeks of cycle-ergometer HIIT performed under normobaric hypoxia (FiO₂: 15%; simulated altitude: 3,000 m) with the same training programme performed under normoxia (FiO₂: 21%). Participants are allocated to one of two groups, stratified by sex, and remain in the assigned group throughout the intervention.

Study Record Dates

• First Submitted: August 27, 2026
• First Posted: September 1, 2026
• Study Start: August 26, 2026
• Primary Completion (Estimated): July 5, 2028
• Study Completion (Estimated): July 5, 2028
• Last Updated: September 1, 2026

Record last verified: 2026-08

Data Sharing

• IPD Sharing: Will not share

Locations

FR (1)