Image copyright Getty Images Image caption The UN estimates that poor nutrition claims the lives of three million children aged under five each year

Most countries in the world are facing a serious public health problem as a result of malnutrition, a report warns.

The Global Nutrition Report said every nation except China had crossed a "malnutrition red line", suffering from too much or too little nutrition.

Globally, malnutrition led to "11% of GDP being squandered as a result of lives lost, less learning, less earning and days lost to illness," it added.

The findings follow on from last year's Nutrition from Growth summit in London.

At the 2013 gathering, 96 signatories made "significant and public commitments to nutrition-related actions" and this report was an assessment of the work that still needed to be done and the progress made.

Image copyright PA Image caption Excess nutrition, a form of malnutrition, is a serious public health issue in industrialised nations

"Malnutrition is an invisible thing, unless it is very extreme," explained Lawrence Haddad, co-chairman of the independent expert group that compiled the report.

"This invisibility stops action happening but it does not stop bad things happening to the children, " he told BBC News.

"It does not stop preventing the children's brains from developing; it does not stop their immune systems from not developing.

"It is a silent crisis and we are trying to raise the awareness of the extent of malnutrition and the damage it does."

The UN World Food Programme estimates that poor nutrition causes nearly half of deaths in children aged under five - 3.1 million children each year.

Dr Haddad, a senior research fellow for the International Food Policy Research Institute, highlighted three areas that the report focused on.

"The first thing we did was to say that we were not just going to focus on undernutrition, which is closely related to hunger, but also overnutrition and obesity," he explained. "Malnutrition just means bad nutrition."

The second thing we did was focus on not just the outcomes, we also focused on the drivers. We looked at underlying factors, such as sanitation, water quality, food security, spending on nutrition and women's status etc.

"The third thing we did was to look at a very specific set of commitments that were made in the 2013 summit that David Cameron hosted in London."

Global problem

The expert group's assessment on global nutrition drew a number of conclusions.

Nutrition disorders Nutrition disorders can be caused by an insufficient intake of food or of certain nutrients, by an inability of the body to absorb and use nutrients, or by overconsumption of certain foods. Examples include obesity caused by excess energy intake, anaemia caused by insufficient intake of iron, and impaired sight because of inadequate intake of vitamin A. Nutrition disorders can be particularly serious in children, since they interfere with growth and development. (Source: World Health Organization)

"First of all, it is really interesting when you put all the data together you find out that nearly every country in the world has crossed a red line on nutrition in terms of it being a serious public health issue," Dr Haddad observed.

"In fact, the only country that has not is China... [but] they are very close to crossing a red line and that data is four to five years old.

He added: "Often you read that it is just a problem that happens in Asia and Africa but, actually, every country in the world is grappling with malnutrition."

"The second big headline is almost half of the countries are grappling with more than one type of malnutrition. About half of the countries in the world are not just grappling with the undernutrition problem but also the overnutrition problem as well.

"Countries like the UK dealt with the undernutrition problem, then there was a bit of a respite but then had to start dealing with overnutrition.

"But about half of the countries in the world are dealing with both of these things at the same time, so that makes dealing with it rather overwhelming and complex."

But he added: "We say that you cannot ignore this anymore and you have got to start strategising around the double burden of over- and under-nutrition."

Last year's meeting in London, nations set a number of targets to be achieved by 2020, including:

ensuring that at least 500 million pregnant women, and children under two years of age, were reached with effective nutrition interventions,

preventing at least 20 million children under the age of five from being stunted

saving at least 1.7 million lives by reducing stunting, increasing breastfeeding, and treating severe acute malnutrition.

Data deficit

Despite the 2013 summit in London raising awareness of the issue of malnutrition, the report's authors found that while global targets were being missed, there was "a lot of very spectacular progress within countries".

Dr Haddad explained: "One of the big messages is that just because globally we are off-track, do not get discouraged because there is some very significant progress being made by very significant countries, such as Bangladesh, Ethiopia, India.

"This is fantastic and if those countries are joined by some other countries then we can easily be back on to achieving global targets."

However, he lamented the quality of the available data: "We say that the state of the data regarding nutrition is terrible.

"We could only find three countries where we could actually find data that properly showed how much was being spent on nutrition.

"Accountability in the nutrition sector is weak because the data is not very good. It is not about naming and shaming, it is about what needs to be done in order to improve accountability."