Muscular dystrophy (MD) encompasses inherited myopathies characterised by progressive skeletal and cardiac muscle degeneration, chronic inflammation, and metabolic dysfunction. While emerging therapies show pre-clinical promise, few reach clinical translation, highlighting the need for supportive interventions to improve function and quality of life (QoL). Nutritional strategies may offer such benefits; however, limited data exist characterising diet in MD or associations with functional outcomes. This study assessed diet, nutritional status, and associations with muscle strength, function, and QoL in MD adults. Adults with MD (n = 39; FSHD = 8, LGMD = 9, Other = 22) and matched controls (n = 15) completed two 3-day food records, strength/function assessments, and QoL questionnaires. Between-group differences were analysed using t-tests or Mann-Whitney U, and associations using Pearson’s r or Spearman’s Rho (p < 0.05). Compared to controls, individuals with MD consumed more energy (89% vs. 35% exceeded RDI, p = 0.023), but less carbohydrate (-21%, p = 0.013), sugar (-31%, p = 0.004), protein (-15%), BCAAs (-31%, p = 0.049), and vitamin C (-43%, p = 0.009). MD participants demonstrated reduced muscle thickness, strength, function, and reported lower QoL and physical capacity (all p < 0.05). Protein intake positively correlated with strength and function (p < 0.05); BCAA intake was associated with lean mass (r = 0.442, p = 0.02) and strength (r = 0.372, p = 0.036). Findings indicate adults with MD consume excess energy but insufficient protein and micronutrients, supporting the need for MD-specific dietary guidance to optimise musculoskeletal health and QoL.