| I don't think you should try to explain the elevated posst-lunch numbers, based on a single incident. Repeat the experiment first and see if it happens again. The reason for the higher numbers is probably completely unrelated to the low-carb breakfast.
Your thinking on a weaker phase one insulin response at lunch time being caused by a low carb breakfast doesn't make sense to me. The phase one response is essentially the mobilisation of stored insulin, which was produced since the previous meal. Eating a low-carb breakfast means that less insulin is required to keep blood glucose normal, so more of it is available for being stored. And the extra stored insulin makes dealing with the next meal easier. A low-carb meal improves the first phase insulin response for the next meal.
Dietary fat is said to slow down the metabolism of carbohydrate, causing blood glucose to rise later on. This could be an issue with you, but you need to test systematically to see if the effect is replicated.
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In my humble opinion  
Type1 since 1977
MDI using Lantus, Novorapid and Actrapid
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