Many employers—including the military—are experiencing systemic workforce capacity and capability challenges. This coincides with a time of declining workforce health, especially among military service entrants, where many performance-limiting health conditions are preventable if healthier behaviours are practised. Effectively tackling complex, interconnected health problems demands a multilevel, multicomponent Whole System Approach (WSA). However, despite recognition of the issues impacting international militaries, current policies and practices supporting healthy, performing workforces have failed. To arrest ill-health trends in personnel, military employers must develop transformational ways to support good health. This paper presents a military workplace WSA model, operationalised through COM-B to specifically target diet behaviour, supporting individual good health, promoting human performance and realising organisational benefits. The challenges of a military occupational setting to individual nutrition practices across the career are discussed. Finally, Impact Value Chain analysis is proposed to monitor system delivery and measure the effectiveness of an integrated, organisation-wide WSA.