Sugary, protein-packed breakfast cereals could lose half their stars and plain yoghurts gain more under a proposed overhaul of the federal government's contentious Health Star Rating system that would see one in five products have their rating changed.

A government advisory committee has released a revamped Health Star Rating calculator that attempts to address various problems with the original, from the over-emphasis on protein to the lack of focus on sugar, as part of a five-year review.

Nutri-Grain could lose stars and yoghurts gain more under the proposed changes. Credit:Peter Braig

The upgraded calculator, if adopted, would slash Kellogg's Nutri-Grain's four-star rating to 2.5, Uncle Toby's Chewy Choc Chip Muesli Bar's four stars to 3.5, and Zooper Dooper Ice Blocks' three stars to the lowest possible score of 0.5.

Products that have been unfairly disadvantaged would get some reprieve, especially nutritious plain yoghurts, with Coles' Greek Style Natural Yoghurt's 1.5 star rating getting boosted to three.