An insulin spike is the very reason many people choose high GI carbs (like Waxy Maize) post workout...taking advantage of the post workout window where your muscles are primed to take on nutrients. However, milk is NOT a high GI beverage although I know many people cling to it as their post workout drink of choice. It stays in the stomach a long time and absorbs relatively slowly....will blood gucose levels rise? Probably. Will they rise fast enough and high enough to induce an insulin spike? Probably not.
Besides the gycemic index of milk being low, if you consider the
gycemic load which is much more indicative of how fast a
given portion will raise blood sugar levels you'll see what I mean.
My calculatins could be off but I'm getting a test portion of somewhere around 35 ounces or around 4 cups of
skimmed milk in order to arrive at the GI below.
Food: Milk (whole/full-fat)
Food Serving Size: 8 fl oz (250ml)
Glycemic Load per Food Serving: 3
Food: Milk (whole/full-fat)
Glycemic Index: 27
Glycemic Index Rating: Low
Food: Milk (skimmed)
Food Serving Size: 8 fl oz (250ml)
Glycemic Load per Food Serving: 4
Food: Milk (skimmed)
Glycemic Index: 32
Glycemic Index Rating: Low
Source
What is Glycemic Load?