1Work out the total 'A' points that can be awarded for each nutrient.

Points are scored on the amount of energy, fat, sugar and sodium that a 100g serving of food contains. The greater the nutrient content the more points are awarded (up to 10 points for each nutrient).

2Work out the total 'C' points for a 100g portion of a food or drink based on its percentage content of fruit, vegetables and nuts and the amount of non-starch polysaccharides (NSP) fibre and protein it contains.

Because there is inconsistency among EU member states and the US in their definitions of fibre, 'C' points also take into account the American Association of Analytical Chemists (AOAC) method of calculating fibre, which includes lignin and resistant starch, which are not classified as NSP. A maximum of five points can be awarded for each C nutrient.

If a food or drink scores 11 or more 'A' points it cannot score points for protein unless it also scores five points for fruit, veg and nuts.

(Still with us?)

3Once the A points and C points have been calculated, one of three equations is used to work out the nutrient profile of a food or drink:

If it scores fewer than 11 A points then its overall score is calculated by subtracting the total number of C points from the total number of A points.

If it scores 11 or more A points, but scores five points for fruit, vegetables and nuts, the score is again calculated by subtracting the total number of C points from the total number of A points.

If, however, a food or drink scores more than 11 A points but also scores fewer than five points for fruit, veg and nuts, the score is calculated by subtracting only the points for fibre and fruit, veg and nuts (not protein) from the total number of A points.

Foods that score four points or more and drinks that score one point or more are considered "less healthy" under NPM and therefore cannot be advertised to children. Foods that score fewer than four and drinks that score fewer than one, including minus scores, can be advertised to children.

(And you thought traffic lights were complicated)