I’m not sure how far I can trust “Food manufacturers, supermarkets and health experts” [http://www.bbc.co.uk/news/health-18034074] to come up with something better than we have now.
They don’t have a great track record.
The system where each food’s nutritional content is listed as a proportion of 100g is fine – it works for me, leave it alone!
European regulations insist on such a system ‘or’ one that provides details per portion. Proportions of 100g tell me the percentage (%) of each nutrient contained and that’s enough for me. 12g of fat per 100g is 12% fat content and I know whether to avoid that product or not. However, 12g of fat per portion tells me nothing!
Portion size is subjective and as far as manufacturers are concerned totally arbitrary. Please do not settle on portion size, pack size, proportion of contents or food shape because they simply do not work.
Let us please have more clarity, don’t allow manufacturers and supermarkets to cloud the issue.