The World Health Organization reports that more than 3.7 billion people are malnourished (WHO 2004) – the largest number and proportion ever reported.Failing to find any mention of that figure in the WHO report I entered "3.7 billion" malnourished in Google. Of the first 20 results, ten cited David Pimentel as the source of the figure and a further one, written by a colleague of Pimentel at Cornell, cited no source. A couple of web pages mentioned that 3.7 billion people suffer from iron-deficiency anaemia, which is "the most common and widespread nutritional disorder in the world," according to the WHO (which instead mentions 2 billion people affected). Nowhere could I find that this is "the largest number and proportion ever reported" (see for example this WHO report, which also cites the 2 billion estimate for 1990-1995).
Pimentel also says:
The United Nations Food and Agriculture Organization indicates that per capita availability of cereal grains, the mainstay of human diets, has been decreasing for the past 20 years (UNFAO 2002; FAOSTAT agricultural data). Despite advances in biotechnology and agricultural technologies, per capita grain production also continues to decline.The truth is that the per capita availability of cereals has remained stable and the per capita availability of all foods has been increasing.