Focus on Fibre Study

Healthy Diets for a Healthy Weight: Exploring Physiological Mechanisms Related to Dietary Fibre

The investigators present a diet intervention study, to be conducted as a within-subject design, with all food and beverages provided, to allow ad libitum feeding to assess impact of diet change on appetite response. The diets will vary in fibre content and type. This study will allow assessment of the physiological impact of dietary fibre on markers of appetite control for body weight, measured from plasma gut hormones. The investigators propose to recruit participants with a poor diet quality (low habitual fibre intake) to additionally examine the time-course of adaptation of the gut microbiome (measured in faecal samples), whilst assessing the impact of added fibre on body weight and subjective appetite scores. This approach is to address the impact of dietary fibre in people living with obesity and food inequalities. The investigators will assess physiological bio-markers of appetite control and their contribution to the development of a gut ecosystem that promotes health. A subsequent period of return to a low fibre feeding will allow assessment of durability of response.

Study Overview

• Status: Recruiting
• Conditions: Appetitive Behavior
• Intervention / Treatment: Other: Phase 1 - Control; Other: Phase 2 - High Fibre; Other: Phase 3 - Low Fibre

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Alexandra Johnstone; Phone Number: 01224 438614; Email: alex.johnstone@abdn.ac.uk
• Study Contact Backup: Name: Claire Fyfe; Phone Number: 01224 438752; Email: c.fyfe@abdn.ac.uk

Study Locations

• United Kingdom
  • Aberdeen, United Kingdom, AB25 2ZD
    • Recruiting
    • Rowett Institute, University of Aberdeen
    • Contact: Alexandra Johnstone, Prof; Phone Number: 01224 438614; Email: alex.johnstone@abdn.ac.uk
    • Contact: Claire Fyfe, Ms; Phone Number: 01224 438752; Email: c.fyfe@abdn.ac.uk
    • Principal Investigator: Alexandra Johnstone, Prof
    • Sub-Investigator: Alexander Ross, Dr

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• healthy but overweight/obese (BMI 28-40kg/m2) males and females (post-menopausal, using the oral contraceptive pill or some form of hormonal contraceptive)
• low habitual fibre intake (<10g/day)

Exclusion Criteria:

Medication exclusion criteria:

• antibiotic use (within the past 3 months due to impact on gut microbiota)
• statins (current)
• aspirin or other NSAIDs or anti-coagulants (current)
• anti-depressants (current)
• smoking or vaping

Medical exclusion criteria:

• Females who are planning to be pregnant, are pregnant or are breastfeeding
• Anyone with food allergies, self-reported food sensitivity or intolerance
• Anyone with coeliac disease or gluten intolerance
• Anyone taking medication which may affect their appetite
• Anyone with an eating disorder
• Anyone with diabetes
• Anyone with a gastrointestinal disorder, kidney disease, liver disease or gout
• Anyone suffering from a psychiatric disorder or any type of substance abuse
• Anyone suffering from unregulated thyroid disease

Other exclusion criteria:

• Anyone following a vegetarian or vegan diet
• Anyone following a weight loss programme (that may be affecting lifestyle, physical activity & diet)
• Anyone with unsuitable veins for blood sampling
• Anyone who is unable to fluently speak, read and understand English
• Anyone who is unable to comply to an alcohol-free diet for 6 weeks

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Control - High Fibre - Low Fibre (CTRL - HF - LF); Phase 1 - CTRL: Control diet with moderate fibre consumption for 13days.; Phase 2 - HF: ad libitum consumption of HF meals for 13days.; Phase 3 - LF: ad libitum consumption of LF meals for 13days.

Other: Phase 1 - Control; Control diet (30% Fat, 15% Protein, 55% Carbohydrate, Fibre rising from 10 to 16g/d). Fed to energy balance (1.5 x Resting Metabolic Rate, RMR).; Other Names: Phase 1 - CTRL; Other: Phase 2 - High Fibre; High Fibre diet (30% Fat, 15% Protein, 55% Carbohydrate, 30g/day Fibre). Fed ad libitum, contains 20g/day pectin (split over breakfast, lunch and dinner) in drinks/yoghurts which will be compulsory to consume and 10g/day fibre coming from the diet provided.; Other Names: HF; Other: Phase 3 - Low Fibre; Low Fibre diet (30% Fat, 15% Protein, 55% Carbohydrate, 10g/day Fibre). Fed ad libitum.; Other Names: LF

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in gut hormones to assess appetite response to dietary fibre	measured by acute and chronic changes in plasma ghrelin and peptide YY (PYY)	At baseline and end of each arm (study days 0, 14, 28 and 42)
Change in subjective hunger to assess appetite response to dietary fibre	measured by acute and chronic changes in appetite using visual analogue scale questionnaires	At baseline and end of each arm (study days 0, 14, 28 and 42)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in gut metabolites (from faecal samples) in response to dietary fibre	measured by changes in faecal short chain fatty acids concentrations	At baseline and end of each arm (study days 0, 14, 28 and 42)
Change in gut microbiome composition (from faecal samples) in response to dietary fibre	measured by changes in bacterial 16S ribosomal ribonucleic acid gene sequencing; 16S rRNA	At baseline and end of each arm (study days 0, 14, 28 and 42)
Change in glycaemic control in response to dietary fibre	measured by acute and chronic changes in plasma glucose and insulin	At baseline and end of each arm (study days 0, 14, 28 and 42)

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in blood metabolites in response to dietary fibre	measured by acute and chronic changes in plasma short chain fatty acids (SCFA)	At baseline and end of each arm (study days 0, 14, 28 and 42)
Change in lipid profile in response to dietary fibre	measured by change in fasting plasma lipid profile (cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides and non-esterified fatty acids (NEFA)	At baseline and end of each arm (study days 0, 14, 28 and 42)
Change in diet markers in response to dietary fibre	measured by change in urinary metabolites	At baseline and end of each arm (study days 0, 14, 28 and 42)
Height	measured in metres	At screening visit only
Change in body weight in response to dietary fibre	measured as weight in kilograms	At baseline and end of each arm (study days 0, 14, 28 and 42)
Change in blood pressure in response to dietary fibre	measured as mmHg on each test day	At baseline and end of each arm (study days 0, 14, 28 and 42)
Change in waist and hip circumferences in response to dietary fibre	measured as in cm with a tape measure on each test day	At baseline and end of each arm (study days 0, 14, 28 and 42)
Change in waist to hip ratio in response to dietary fibre	waist and hip measures will be combined to report waist to hip ratio	At baseline and end of each arm (study days 0, 14, 28 and 42)
Change in Body Mass Index (BMI) in response to dietary fibre	weight and height measures will be combined to report BMI in kg/m^2	At baseline and end of each arm (study days 0, 14, 28 and 42)
Change in gastrointestinal symptoms in response to dietary fibre	measured daily, at end of day, using questionnaires	every day of study (42days)
Change in appetite in response to dietary fibre	measured daily, at end of day, using visual analogue scale questionnaires	every day of study (42days)
Change in free-living glycaemic control in response to dietary fibre	measured using continuous glucose monitoring (CGM)	every day of study (42days)
Change in food intake	measured using weighed intake records	at screening (7days) and every day of study (42days)

Collaborators and Investigators

• Sponsor: University of Aberdeen
• Investigators: Principal Investigator: Alexandra Johnstone, Prof, Rowett Institute, University of Aberdeen; Principal Investigator: Alexander Ross, Dr, Rowett Institute, University of Aberdeen

Study record dates

Study Major Dates

• Study Start (Actual): June 14, 2022
• Primary Completion (Estimated): December 31, 2023
• Study Completion (Estimated): December 31, 2023

Study Registration Dates

• First Submitted: June 17, 2022
• First Submitted That Met QC Criteria: July 4, 2022
• First Posted (Actual): July 8, 2022

Study Record Updates

• Last Update Posted (Actual): November 1, 2023
• Last Update Submitted That Met QC Criteria: October 31, 2023
• Last Verified: October 1, 2023

More Information

Terms related to this study

• Keywords: gut microbiome; appetite control; fibre; glycaemic control
• Other Study ID Numbers: 813

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No