A Randomised, Controlled Trial of a Low-energy Diet for Improving Functional Status in Heart Failure With PRESERVED Ejection Fraction Preserved Ejection Fraction

Meal replacement diet containing \~850 kcal/day (40% protein, 50% carbohydrate, 10% fat) supplied by Counterweight® (www.counterweight.org).The meal replacement plan will comprise of 3-4 meal packs/day (to equate to 850 kcal) with sweet and savoury options, and an allowance of 100ml semi-skimmed milk or a non-dairy alternative.

CMR scanning performed on a 3T MRI scanner. Standardised protocol incorporating cine functional assessment to determine LV mass, systolic function and left atrial volumes; global systolic strain and diastolic strain rates will be assessed by tagging and with tissue tracking analysis from cine images, adenosine rest and stress myocardial perfusion to assess reserve index and qualitative perfusion defects as previously described, aortic distensibility and pulse wave velocity to measure aortic stiffness, delayed contrast enhancement for assessment of LV fibrosis and evidence of previous myocardial infarction. Myocardial and liver triglyceride content will be assessed using the modified Hepafat® sequence or 1H MR spectroscopy at the inter ventricular septum. DIXON technique for the quantification of visceral adiposity and subcutaneous adipose tissue. Cardiac 31P magnetic resonance spectroscopy imaging to assess cardiac muscle energetics according to a standardised operating procedure

Comprehensive transthoracic echocardiography, including: tissue Doppler indices of diastolic filling and speckle tracking for systolic and diastolic strain/strain rate, exclusion of valvular abnormalities, assessment of LV size and function

Collection of blood samples from each participant to characterise the participant's health status and fibroinflammatory markers.

An ECG will be obtained to assess for baseline rhythm.

Accelerometer (GeneActiv) measured daily activity levels continuously for 7 consecutive days.

Supervised 6MWT will be performed with symptom assessment using dyspnoea scale (Borg's).

Skeletal muscle strength will be measured using a cybex dynamometer.

Quality of life and HF symptoms will be assessed using the Minnesota Living with Heart Failure (MLWHF) questionnaire, which is used as a standardised measure of self-reported health status, and HF symptoms and is considered to have a good discriminatory power and validity

Participants will be assessed for presence of sarcopenia using the Strength, Assistance with walking, Rise from a chair, Climb stairs and Falls (SARC-F) questionnaire. It is a robust tool for diagnosis of sarcopenia and prediction poor physical function, with excellent specificity in multimorbid individuals.

Frailty will be assessed using the Edmonton Frail Scale (EFS). The EFS is a multidimensional frailty assessment which assesses multiple domains of frailty including functional independence, social support, cognition, medication use, and mood.

Participants in the MRP and control groups will be invited to attend a focused semi-structured, 1-2-1 interview aimed to elicit barriers and enablers to the MRP and describe their perspective on the relationship between healthy eating and health interview during the 12-week visit. Participants who complete or drop out will be eligible. Inclusion of participants in the control arm will allow us to compare the experiences of MRP versus health coaching and detect any specific issues people face when trying to introduce lifestyle changes themselves.