When asked about sustainable human development , which is usually 6 marks or so , I think you need to address sustainability , human development and health + global health!
This is how I would do this type of question !
How food security amongst children could impact on a country's ability to achieve sustainable human development.( 6 marks)
With promoting food security , children are less likely to be suffering from malnutrition(physical health) , because of the availability of nutritious food and thus increasing morbidity(global health) due to lack of food security(. This means children are more likely to go to school and enhance capabilities and expand choices ( human development) , rather than being bed-ridden due to malnourishment . This means that they are more likely to pass their knowledge to the current generation , without compromising the needs of the future generations , enabling social sustainability. Furthermore, when food security is promoted, children don't have to travel long distances to find food , but rather go to school and interact with other children ( social health) , and thus be in the life of the community (human development) . Therefore , they will be able to share their ideas and feelings and thus enable social sustainability , for the current generation ,without compromising the needs of the future generation*
But I think the general trend has been that VCAA will separately ask a question on elements of sustainability.
Hope this helps!
*this is not the best answer