[Elizellen]

I entered that recipe as a custom food in my fitday and it works out as having **3 net carbs per muffin. but the cream cheese I buy has only 1.6 carbs per 100 grams/3.5 ounces.

Piladelphia brand has more carbs in it - check your packet but the UK philadelphia has 3.2 net grams per 100 grams, so a muffin made from it would have more net carbs!!

Each muffin has about half of your daily allowance of cheese and *2 servings of splenda, so they would need to be 'rationed' so as not to exceed your cheese and sweetener amounts per day.
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** Edited to confirm that my carb count above is wrong and each muffin would have 1.7 net carbs, not 3 as I wrote initially

* also each muffin would have one serving of splenda, not 2 as I wrote above