This study develops a system dynamics based simulation model to understand dynamics of food security of Pakistan assuming exogenous GDP. The management of sustainable food security in Pakistan is based on the available agricultural land, size of its population and productivity of the factors of production. The natural endowment of agricultural land in use will decrease over time limiting food supply in Pakistan. Increased productivity of land and labor through education and technology may help improve situation. On the other hand, the sheer size of the population will worsen the food security situation. The simulation results suggest that economic growth rate of 4.75% or more coupled with high public spending on human development, higher than current levels of 2% on education and 1% on health, is a must for sustainable food security in Pakistan. Such an economic growth rate and commitment to human development will not only improve human development indicators but will also ensure sustainable food security. However, one critical finding is that Pakistan may not be able to provide the threshold calories to its population required for a healthy living. This clearly suggests persistent prevalence of malnutrition even though it may reduce over time.