Intermittent Carbohydrate Restriction in Cardiometabolic Health
ConditionObesity and Overweight
Trial statusRecruiting
Trial phaseNot applicable
Trial typeInterventional
Biological sexAll
Age18-65
SponsorUniversity of Bath
About this trial
Metabolic conditions, such as heart disease, type 2 diabetes, and metabolic syndrome, are among the leading causes of disability and mortality worldwide. Identifying innovative lifestyle strategies to reduce metabolic risk remains a public health priority. Further research is essential to understand how low carbohydrate intake influences human metabolism and how intermittent carbohydrate restriction impacts weight loss and metabolic health markers.
This study will investigate two interventions that restrict dietary carbohydrate intake on different schedules, examining their effects on metabolic health and energy balance in adults with abdominal overweight or obesity. The physiological mechanisms potentially underlying these effects will be explored by measuring a range of lifestyle and metabolic health parameters in both free-living and laboratory settings. A digital behaviour-change intervention will be incorporated after the dietary intervention to assess whether any metabolic effects can be sustained over time.
The study employs a three-arm parallel-group design consisting of a two-week lifestyle monitoring phase, a four-week dietary intervention, and a four-week digital intervention, with four laboratory visits throughout each phase. During the dietary intervention, participants will be allocated to one of three groups: (i) carbohydrate restriction (\<8% of energy intake) on two consecutive days per week, (ii) carbohydrate restriction after 4 pm each day, or (iii) no dietary changes.
Dietary intake, physical activity, and glucose levels will be monitored through wearable devices in free-living conditions. The digital intervention will use a mobile health application that provides individualised lifestyle recommendations and education based on data collected in free-living conditions. Laboratory-based measures will include anthropometry, body composition scans, indirect calorimetry, blood pressure monitoring, fat biopsies, and postprandial sampling of blood and expired air.
Eligibility criteria
This trial accepts healthy volunteersQualifiers
Waist circumference of ≥94 cm (37 inches) if male and ≥80 cm (31.5 inches) if female, or BMI above 25 kg/m2
Fat mass index (FMI) of >6 kg/m2 for males, and >9 kg/m2 for females
Aged between 18-65 years
Has maintained a stable weight in the last three months (<3% change in body mass)
Disqualifiers
Has a body weight of ≥120kg
Plans to undertake other lifestyle modifications during the study to manage weight (e.g. changes in dietary intake or activity levels)
Current or previous eating disorder
Diagnosed with major chronic conditions (e.g. type 2 diabetes, coronary heart disease, cancer, chronic kidney disease, etc.)
Trial design
Design model
Parallel
Treatments tested in this trial
5:2 carbohydrate restriction
Other interventionCarbohydrate ingestion restricted to \<8% of energy intake on 2 self-selected consecutive days each week over 28-30 days. Ad libitum dietary amount, type and pattern followed on the remaining 5 days each week.
Early time-restricted carbohydrate intake
Other interventionCarbohydrate intake restricted to \<8% of energy intake after 4pm each day for 28 days. Ad libitum dietary amount, type and pattern followed before 4pm.
Treatment groups
36 Participants
are divided into 3 treatment groupsGroup A: 5:2 carbohydrate restriction (5:2CR)Experimental treatment 1 intervention
Group B: Early time-restricted carbohydrate intake (eTRC)Experimental treatment 1 intervention
Group C: Lifestyle maintenance (control)No intervention 0 interventions
Trial outcomes
Primary outcomes
1
Post Prandial Triglyceride Area Under the Curve (AUC)
Plasma triglyceride concentrations assessed postprandially for 5 hours after a mixed meal test
Time frame
Pre and post intervention (4 weeks)Secondary outcomes
1
Fat Mass
Measured in kilogrammes using Dual Energy X-ray Absorptiometry
Time frame
Pre and post intervention (4 weeks)2
Lean Body Mass
Measured in kilogrammes using Dual Energy X-ray Absorptiometry
Time frame
Pre and post intervention (4 weeks)3
Fasting and Post Prandial Glucose Concentration
Plasma glucose concentrations assessed after an overnight fast, postprandially for 5 hours after a mixed meal test
Time frame
Pre and post intervention (4 weeks)4
Fasting and Post Prandial Insulin Concentration
Plasma insulin concentrations assessed after an overnight fast, postprandially for 5 hours after a mixed meal test
Time frame
Pre and post intervention (4 weeks)Other outcomes
1
Physical Activity Energy Expenditure (kJ or kcal)
Assessed using combined heart rate and accelerometery wearable monitor (Actiheart™) in free-living conditions.
Time frame
1 week during baseline monitoring, and weeks 1 and 4 of the intervention2
Time Spent in Different Physical Activity Intensities (minutes)
Assessed using combined heart rate and accelerometery wearable monitor (Actiheart™) in free-living conditions
Time frame
1 week during baseline monitoring, and weeks 1 and 4 of the intervention3
Dietary Intake
Dietary records manually kept by study participants
Time frame
1 week during baseline monitoring, and weeks 1 and 4 of intervention4
Interstitial Glucose
Continuous glucose records will be used to capture interstitial glucose before and during the intervention
Time frame
2 weeks during baseline monitoring, 2 weeks during weeks 3-4 of interventionSponsors and contacts
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Source ClinicalTrials.gov