There are two ways to approach this question.
First, we can ask why it was generally possible for less developed countries (LDCs) to increase their food consumption while developed countries (DCs) could not. To answer this, think about the starting points for food consumption in these different types of countries. A DC is, by definition, rich. Its people will already be eating, for the most part, all the food they need and want. There is not much that can be done to increase their consumption because it is already near to maximum. By contrast, LDCs start from near to the bottom. Many of their people have very little food. This means that there is much more room for an LDC to increase its consumption compared to a DC.
Second, we can ask what specific causes made more food available to people in LDCs. Here, there are two main factors. First, there is the “green revolution” of the 1960s and 1970s. During this time, staple crops eaten by people in LDCs were greatly improved through scientific means. This made it much easier for large quantities of food to be produced. Second, there is globalization. Globalization of the economy has, in general, started to help LDCs become prosperous and more able to afford food. As countries like China have improved their economic status, their people have come to be able to have more food.
For these reasons, LDCs have increased their consumption much more than DCs have.