Professor Lang is a member of the UK government's newly formed Food Council.
"Essentially, what we are dealing with at the moment is a food system that was laid down in the 1940s," he told BBC News.
"It followed on from the dust bowl in the US, the collapse of food production in Europe and starvation in Asia.
"At the time, there was clear evidence showing that there was a mismatch between producers and the need of consumers."
Professor Lang, from City University, London, added that during the post-war period, food scientists and policymakers also thought increasing production would reduce the cost of food, while improving people's diets and public health.
I think there is a need to spend more time on saving food, and not wasting it in the future. We should be more diligent about what we have in our refrigerators and learn to appreciate and understand just how easy it can be to make the most of any kitchen pantries.
- Oil and energy: "We have an entirely oil-based food economy, and yet oil is running out. The impact of that on agriculture is one of the drivers of the volatility in the world food commodity markets."
- Water scarcity: "One of the key things that I have been pushing is to get the UK government to start auditing food by water," Professor Lang said, adding that 50% of the UK's vegetables are imported, many from water-stressed nations.
- Biodiversity: "Biodiversity must not just be protected, it must be replaced and enhanced; but that is going to require a very different way growing food and using the land."
- Urbanisation: "Probably the most important thing within the social sphere. More people now live in towns than in the countryside. In which case, where do they get their food?"