The cognitive processes responsible for effortful behavioural regulation are known as the executive functions, and are implicated in several factors associated with behaviour control, including focussing on tasks, resisting temptations, planning future actions, and inhibiting prepotent responses. Similar to muscles, the executive functions become fatigued following intensive use (e.g. stressful situations, when tired or busy, and when regulating behaviour such as quitting smoking). Therefore, an individual may be more susceptible to engaging in unhealthy behaviours when their executive functions are depleted. In the present study we investigate associations between the executive functions, snack food consumption, and sedentary behaviour in real time. We hypothesise that individuals may be more susceptible to unhealthy snacking and sedentary behaviours during periods when their executive functions are depleted. We test this hypothesis using real-time objective within-person measurements.