Controlling our blood glucose is difficult at the best of times. But sometimes, no matter what we do, it seems like some food is just out to get us. 

Many of us have experienced this with pizza and chocolate, and you bolus for it, you eat it, and all is great. 

Then 45 minutes later, your Dexcom G6 shows your sugars as a picture of a hyperglycemic mountain range instead of that flat line you expected to see.

Well, as with everything that happens to our blood sugars, there's some science for that.

Pizza and how the different levels of fats proteins and sugars can impact your blood glucose control and CGM readings


You need to consider how fats & protein impact your blood sugars.

But fats aren't glucose? How does something that isn't even glucose make my blood glucose go up?

Well, dear friend, this is where our digestive system comes in. 

Proteins and fats can slow down the rate at which your stomach empties into your small intestine, which means it's going to take longer for the nutrients to be absorbed. Also, when you have a very fatty meal, there are just too many molecules there for the small intestine's surface area to handle, which means they have to take turns being absorbed. 

The molecules are queuing up to board the rollercoaster of your blood sugar because they can't all go through at the same time!

A queue, fat molecules and glucose molecules both want to go through the same absorption cells, but have to wait until there is room.

Crucially, this means that all of the carbs you just ate can't be absorbed straight away and will be entering your system later.

In terms of fats, our digestive system processes them and starts to increase the level of triglycerides in our blood steadily. When the liver detects this, it initiates a degree of insulin resistance and secretes glucose - as explained here.

This means that when you eat foods like Pizza and Chocolate with equal or significant carb and fat levels, you need to prepare for two spikes on your Freestyle Libre or CGM.

You'll have an initial spike from fast-digesting simple carbohydrates, like bread, and then you're going to get a second spike. The second spike comes from the glucose generated due to the fats in the cheese and toppings. 

 molecular image of glucose and fats showing the differences and how complex fats are


But it's not just applicable to pizza.

This second spike threat applies to all foods with a fat content, like chocolate. For example, if you've got a dish that's 70% carbs and 30% fat, then you've got a second spike coming from the part of the meal that was 30% fat. If you're eating something that's almost pure fat, like an incredible dessert, you probably won't have much of a first spike.

But you're going to have a super stubborn second spike, fuelled by the long and slow release of the glucose derived from the fats.


What can we do?

Ultimately, everybody digests at different speeds and reacts to things differently. Some of us get a second spike after 30 minutes, and for others, it can take up to 2 hours - but the average is about an hour.

You need to discuss with your nurse or doctor before you make any decisions, as there are an incredible amount of variables that can affect the success of anything you do. 

A study by Penn State backs up the idea of split-bolusing - which is now quite common.

If you decided you needed, say, five units for a pizza, you'd take three just before and then two an hour later or when you expected spike two to come around. Split-bolusing is effectively micro-managing. But again, this might not be appropriate for you, and you need to check with your healthcare professional before you try this. 

Of course, if you're using an Omnipod, a Touchcare Nano, or other pumps, this is much more complicated, and you'll definitely need to raise it with your healthcare professional. For individuals on these, you need to involve your basal insulin and different delivery profiles, so you must calculate this with your doctor. 


Should I avoid these foods?

Absolutely not! Fats are essential for many critical body functions, such as protecting your vital organs, and you need to be eating them.

It's not a case of avoiding food. It's a case of better understanding the impact a meal might have on your blood glucose control. As you progress on your T1D journey and understand your diabetes better, you'll be more able to accurately estimate the impact foods with different carb & fat levels have on you.

Remember, many technologies can help you with this; your Freestyle Libre, Dexcom G6, or Eversense CGM, and even carb-counting apps like MyFitnesspal

This way, you can eat the foods you love and look after your diabetes in the most effective way. This is better for our mental health. Ultimately, we come first, and our diabetes comes second - but we treat our diabetes respectfully.

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