Protein Intake Is Associated with Adiposity and Quality of Life in Adults with Becker Muscular Dystrophy.

BACKGROUND & AIMS: Becker Muscular Dystrophy (BMD) is a rare X-linked genetic condition characterised by reduced dystrophin expression, causing progressive skeletal muscle and functional decline, and ultimately poor quality of life (QoL). With no current pharmacological cure, practical easy-to-implement strategies are needed to improve QoL in BMD. Increasing dietary protein intake is beneficial in other clinical populations, exhibiting positive impacts on lean body mass and self-reported pain. While progressive muscle deterioration is a hallmark of BMD, less is known about the interaction between nutritional status, body composition, physical function and QoL in BMD. Therefore, this study aimed to characterise dietary intake and explore relationships between dietary factors and readouts of body composition, muscle size/strength and QoL. METHODS: Adult males with BMD (n = 20) and age-matched controls (n = 12), completed 2 food diaries ∼6 weeks apart with instructions to state exact quantities, brand names and cooking methods, a battery of physical tests assessing body composition, muscle size, strength, and function, as well as validated questionnaires on perceived physical function, pain/fatigue, QoL, and nutritional knowledge. RESULTS: Adults with BMD reported 29% lower daily energy intake, 25-30% lower carbohydrate and fat intakes, and 21% lower relative protein intake (0.86 vs. 1.08g/kg/day) than controls (all p < 0.05). Only 10% of the BMD group met the minimum end of The European Society for Clinical Nutrition (ESPEN) recommended protein intake range for disease-related muscle loss (1.2-1.7g/kg/day). The BMD group exhibited greater fat mass index (FMI) (9.31kg/m2 vs. 6.30kg/m2) and 95% of BMD were classified obese or overweight, however no differences in lean mass were observed. Individuals with BMD also exhibited lower tibialis anterior muscle thickness, strength, and physical function, and reported reduced QoL, lower limb function and activities of daily living, along with higher pain and fatigue (67-77%, all p < 0.05). When controlling for age, total energy intake and self-reported physical activity, protein intake (g/kg/day) was negatively associated with fat mass index (r = -0.698, p = 0.017) and positively associated with SF36v2 quality of life (r = 0.503, p = 0.040), whilst BMI was positively associated with pain (r = 0.684, p = 0.002). CONCLUSION: Our results show adults with BMD report lower overall caloric and relative protein intake than non-dystrophic individuals, with protein intake substantially lower than guidance for other muscle-wasting conditions. Adults with BMD also displayed higher levels of adiposity, reported higher fatigue and pain as well as lower quality of life. The observed positive associations between relative protein intake and QoL, together with the negative associations between relative protein intake and adiposity, support further investigation into the role of protein intake in adults with BMD. Prospective and intervention studies are needed to establish the true nature of these relationships to inform nutritional recommendations for the BMD population.