Feasibility and Metabolic Effects of a 5:2 Fasting Intervention in Women With Breast Cancer During Radiotherapy

Study Overview
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Brief Summary
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The intervention consists of the adoption of a 5:2 intermittent fasting diet during radiotherapy of breast cancer patients. The aim of the study was to assess the feasibility of this intervention and its impact on body composition and selected metabolic blood parameters.

Detailed Description
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The 5:2 intermittent fasting (FAST) intervention consisted of two nonconsecutive days of fasting per week that could be chosen freely according to the patient's weekly schedule. The minimum amount of time to count as a fasting day was 24 hours, but patients were advised to aim for a complete fasting day including the nights before and after that day. On a fasting day, only water and unsweetened tea or coffee was allowed. However, given that fat is the macronutrient interfering the least with the metabolic adaptions to fasting, while carbohydrates disturb the most [26], patients were allowed to consume small amounts of bone broth/meat broth, coconut oil, butter/ghee or heavy cream as an emergency plan, i.e., in case that they felt they needed some energy-containing foods to complete an initiated fasting day. The primary study outcome was the feasibility of the FAST intervention and its effects on longitudinal body composition changes from baseline until the final week of radiotherapy (body mass, fat mass, fat-free mass, muscle mass, extracellular and total body water). Secondary endpoints were absolute changes in metabolic parameters, hormones, and overall quality of life scores in the FAST group. As a surrogate marker for insulin resistance, the triglyceride-glucose index (TyG) was calculated according to TyG=ln⁡(fasting triglycerides [mg/dl]×fasting glucose [mg/dl]/ 2).

Official Title
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Feasibility and Metabolic Effects of a 5:2 Fasting Intervention in Women With Breast Cancer During Radiotherapy

Conditions
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Breast Cancer

Intervention / Treatment
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* Radiation: Curative radiotherapy
* Behavioral: 5:2 intermittent fasting


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Non-metastasized breast cancer Indication for curative radiotherapy Exclusion Criteria: metallic body parts that would interfere with electric bioimpedance (BIA) measurements difficulties with understanding the aims of the study

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: FAST<br>5:2 intermittent fasting group | Radiation: Curative radiotherapy<br>* Curative radiotherapy as indicated by the patient's disease and prescribed by the treating radiation oncologist<br>Behavioral: 5:2 intermittent fasting<br>* Two nonconsecutive days of fasting per week that could be chosen freely according to the patient's weekly schedule.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Dropout rate in the FAST intervention group | Used to measure feasibility. The intervention is rated as feasible if dropout rate is <30% | Through study completion, an average of 5 weeks | 
| Longitudinal changes in body mass | Body mass (in kg) is measured by a bioimpedance device with an integrated scale (seca mBCA, seca Deutschland, Hamburg, Germany). | Through study completion, an average of 5 weeks | 
| Longitudinal changes in fat-free mass | Fat-free mass (in kg) is estimated by a bioimpedance device with an integrated scale (seca mBCA, seca Deutschland, Hamburg, Germany). | Through study completion, an average of 5 weeks | 
| Longitudinal changes in skeletal muscle mass | Skeletal muscle mass (in kg) is estimated by a bioimpedance device with an integrated scale (seca mBCA, seca Deutschland, Hamburg, Germany). | Through study completion, an average of 5 weeks | 
| Longitudinal changes in total body water | Total body water content (in L) is estimated by a bioimpedance device with an integrated scale (seca mBCA, seca Deutschland, Hamburg, Germany). | Through study completion, an average of 5 weeks | 
| Longitudinal changes in extracellular water | Extracellular water (in L) is estimated by a bioimpedance device with an integrated scale (seca mBCA, seca Deutschland, Hamburg, Germany). | Through study completion, an average of 5 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change between baseline and final (average 5 weeks) TyG index | As a surrogate marker for insulin resistance, the triglyceride-glucose index (TyG) is calculated according to TyG=ln⁡(fasting triglycerides [mg/dl]×fasting glucose [mg/dl]/ 2) | Through study completion, an average of 5 weeks |