According to the new Global Hunger Index (GHI), 805 million people in the world suffer from chronic hunger. This number is a slightly lower estimate than in previous years, and shows that the world is on track to meet the Millennium Development Goal (MDG) of halving the proportion of hungry people by 2015 relative to 1990 levels. Still, these findings, along with the shocking number that more than 2 billion people are malnourished and suffer from lack of micronutrients, also demonstrate how important it is that the post-2015 development goals focus on better nutrition and eradication of hunger much further.

Of all the issues that call for our attention, nutrition is exactly the right issue to focus on. Not only is under-nutrition the largest single contributor to child mortality worldwide, it is also morally wrong that in a world with sufficient food, more than 800 million remain hungry. But the most important reason we ought to focus on nutrition is the one you haven't heard. It simply turns out that nutrition is the best way to spend a dollar to do good in the world.

We know this from the Copenhagen Consensus economics project. It asked more than sixty of the world's top economists and four Nobel Laureates to look at a large number of world challenges and find where we could do the most good. Of all the solutions, they found nutrition to be the very best.

Why? Because nutrition is not just about avoiding hunger and securing human decency. If you don't get enough food, you don't develop - we see this in kids being stunted, that is growing less than they should. Lack of food and micronutrients also affects their muscle and brain growth; it damages spatial navigation and memory formation, leading to loss of cognitive abilities. This prevents the affected from reaching their full potential as grown-ups, resulting in the loss of billions of dollars in productivity in the developing world.

As it turns out, tackling nutrition is the most cost-effective solution around, because it has massive benefits for a tiny price tag.

There are nearly 180 million preschool-age children who do not get vital nutrients. But there are ways to help this next generation of kids. John Hoddinott of the International Food Policy Research Institute and Peter Orazem of Iowa State University show how an investment of $3 billion annually could purchase a bundle of nutrition interventions, including micronutrient provision, complementary foods, treatment for worms and diarrheal diseases, and behavior-change programs, all of which could reduce chronic under-nutrition by 36% in developing countries.

Achieving this means ensuring more than 100 million children could start their lives without stunted growth. And the benefits would stay with them for life.

We can see this perhaps most clearly in the recent follow-up of an experiment in Guatemala. Beginning in 1969, preschool children in four villages got good nutrition whereas similar children in villages nearby did not. When researchers followed up 35 years later - when the children had reached their 30s and 40s - they observed dramatic differences in the individuals who were better-nourished as children.

The well-nourished children stayed in school longer and scored higher on tests of cognitive skill in adulthood. They had better outcomes in the marriage market, higher wages, and were more likely to be employed in higher-paying skilled labor and white-collar jobs. If they were women, they had fewer pregnancies and smaller risk of miscarriages and stillbirths. Fundamentally, they had dramatically better lives.

This is all because of nutrition - that was the only difference. Their bodies and muscles grew faster, their cognitive abilities improved, they could pay more attention in school and hence stayed there longer. When compared to stunted kids, the well-nourished kids had three times the income as adults. They were more productive, had smaller families and began a virtuous circle of dramatic development.

Applying the Guatemala experiments and several others across the developing world, economists can estimate the benefits to a significant step-up of today's nutrition policies. Ultimately, when all benefits are translated into economic terms, every dollar spent on nutrient provision will likely do $59 worth of global good. So while this solution rarely receives much fanfare, a wide-scale effort could make a world of difference, enabling developing nations to prosper.

At a London summit called "Nutrition for Growth" held in June 2013, a coalition of NGOs, InterAction, pledged $750 million of private funds. They justified the focus on investments in nutrition partly on the findings from the Copenhagen Consensus. Now we need to convince UN leaders to keep the ball rolling for the next set of development goals. Nutrition might not be the 'sexiest' issue on the global agenda, but because it can do so much good, it should be our number one priority.