Effect of varying carbohydrate and fat intake on endurance athlete performance and health

Effect of a 12 week low carbohydrate, high fat, high carbohydrate or low carbohydrate diet supplemented with polyunsaturated fats on endurance athletes performance and health markers

Status

Active, not recruiting

Phases

Unknown

Study type

Interventional

Source

ISRCTN

Registry ID

ISRCTN70987680

Enrollment

Registered

2016-08-10

Start date

2015-03-01

Completion date

Unknown

Last updated

2023-09-26

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Sports performance, fuel utilization and health (haematological, cardiovascular, inflammation and bone health) Nutritional, Metabolic, Endocrine

Interventions

Participants are allocated into one of three study arms, depending on which group they would be able to adhere to. Group 1: Participants follow a low carbohydrate diet, which involves

Eligibility

Sex/Gender

Male

Inclusion criteria

Inclusion criteria: 1. Male 2. Age 18-40 years 3. Endurance athlete for past 12 months completing minimum 7hrs/week training

Exclusion criteria

Exclusion criteria: 1. Not an endurance athlete 2. Already consuming a low carbohydrate high fat diet 3. Unable to complete a 100km time trial 4. Any health conditions such as heart problems, blood pressure 5. Disorders related to enzyme production

Design outcomes

Primary

Measure	Time frame
1. Nutritional intake (dietary fat, carbohydrate and protein) is measured using the nutritics dietary analysis programme at baseline and 12 weeks 2. Fuel utilization measured through respiratory exchange ratio (RER) using the moxus, was recorded at baseline and 12 weeks 3. Critical power is measured through a 100km time trial on a cycle ergometer at baseline and 12 weeks 4. Blood lactate is measured using lactatepro and was taken at the start of the time trial and every 20km during the time trials undertaken, at baseline and 12 weeks	—

Measure

Time frame

1. Nutritional intake (dietary fat, carbohydrate and protein) is measured using the nutritics dietary analysis programme at baseline and 12 weeks 2. Fuel utilization measured through respiratory exchange ratio (RER) using the moxus, was recorded at baseline and 12 weeks 3. Critical power is measured through a 100km time trial on a cycle ergometer at baseline and 12 weeks 4. Blood lactate is measured using lactatepro and was taken at the start of the time trial and every 20km during the time trials undertaken, at baseline and 12 weeks

—

Secondary

Measure	Time frame
1. Body composition (fat and muscle mass) is measured using a DXA scanner at baseline and 12 weeks 2. Bone density and mass is measured using a DXA scanner at baseline and 12 weeks 3. Blood cholesterol is measured using the randox method at baseline and 12 weeks 4. Serum C reactive protein is measured through ELISA at baseline and 12 weeks 5. Hematology of blood is measured using a hematology analyser at baseline and 12 weeks	—

Measure

Time frame

1. Body composition (fat and muscle mass) is measured using a DXA scanner at baseline and 12 weeks 2. Bone density and mass is measured using a DXA scanner at baseline and 12 weeks 3. Blood cholesterol is measured using the randox method at baseline and 12 weeks 4. Serum C reactive protein is measured through ELISA at baseline and 12 weeks 5. Hematology of blood is measured using a hematology analyser at baseline and 12 weeks

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Countries

Ireland

Outcome results

None listed

Source: ISRCTN (via WHO ICTRP) · Data processed: Feb 4, 2026