A 45-year-old man with no significant past medical history presents to his GP with a 3-month history of exertional dyspnoea and orthopnoea. Examination shows raised JVP, bilateral basal crackles and pitting ankle oedema. Echocardiogram reveals LVEF 25% with global hypokinesis. Coronary angiography shows no obstructive disease. Which of the following lifestyle measures is most appropriate as part of his management?