Here you can download a resent food industry (IGD) report on portion size.
The report can be of use to those working in nutrition, product design, CSR, or regulatory positions involved in determining portion sizes for foods within the grocery and food service sectors.
Portion size is important for food labelling purposes and from the perspective of nutrient and energy intake. The increasing prevalence of obesity has focused attention on intake in relation to portion size and raised the question of whether guidance is needed on setting portion sizes for particular foods.