A High-PRotein Mediterranean Diet and Resistance Exercise for Cardiac Rehabilitation: a Pilot Feasibility Study

BACKGROUND Cardiovascular disease (CVD) in the UK is behind 1 in 4 deaths/year (>150,000 people), with coronary heart disease (CHD) being the most common type [1]. In addition to the loss of life, the economic cost of CVD is considerable; in 2015 healthcare for CVD alone in the UK amounted to £10.9 billion with a further £7.7 billion lost from the economy due to productivity loses [2].

Mortality figures due to CHD have been reduced recently, in part due to increased provision of cardiac rehabilitation (CR), a therapeutic approach based on exercise training to improve cardiac function, plus advice regarding smoking cessation, dietary changes and weight loss [3].

RATIONALE Most of the evidence on the benefit of CR examines the links between exercise and CV morbidity and mortality [4]; however, there is considerable evidence showing improvements in markers of cardiovascular risk through different dietary strategies [5]. Of particular relevance, results from studies on both the primary and secondary prevention of CVD suggest Mediterranean diet-based approaches are the most adequate to treat these patients [6-13].

Obesity, and in particular, visceral adiposity, is associated with cardiometabolic (CM) risk markers (e.g., high cholesterol and triglycerides levels, HbA1c, etc.) [14-16], however, an "obesity paradox" appears to exist in the cardiac population, where increased mortality has been linked to low body mass index (BMI) [17, 18]. However, low lean body mass (LBM) is the likely driver of this phenomenon due to sarcopenia, a progressive loss of LBM associated with aging [19]. Patients with a combination of low LBM and abdominal distribution of body fat, known as sarcopenic obesity (SO), are at greater risk of CVD, exacerbated in CR [20-23]. Thus, increasing relative LBM content, rather than simply promoting weight loss, may be an appropriate target in CR patients.

One particular barrier to maintaining or accruing LBM is the presence of anabolic resistance in older adults, which can result in a reduced muscle protein synthetic (MPS) response to both exercise and the ingestion of currently recommended intakes of protein [24]. Protein intakes above currently recommended levels (1.0-1.5 g/kg/BW) [25] combined with sufficiently intense resistance training [26] can overcome this anabolic resistance and positively influence muscle mass, ultimately leading to greater improvement in body composition, when accompanied by a reduction in total body fat mass [27].