The Pizza Effect: A guide to how food types influence blood sugar levels

What is the Pizza Effect?

The "Pizza Effect," a term coined by our type one diabetes community, is something we will all experience.

The Pizza Effect is the surprise second spike in blood glucose levels after a meal. Usually, when we only expected one spike from that meal. You'll see this on your Dexcom or Freestyle Libre around one to two hours after your meal.

Generally, we bolus for carbs, eat a delicious pizza and then discover our blood glucose levels have spiked on our CGM an hour or two later. Frustratingly, this is usually the start of the "corrective rollercoaster" where we can't reign in our blood glucose levels.

How does the Pizza Effect impact our mental wellbeing?

Chiefly, the Pizza Effect can cause a rollercoaster of high and low blood glucose levels after a meal, fueling anxiety and predisposing us to a negative relationship with those foods.

This negative relationship with food adds to the emotional burden of type one diabetes and contributes to daily stress.

Often, that surprise high glucose alarm from our Dexcom or insulin pump will antagonize us where we weren't expecting that frustrating second spike.

We may even refuse to go out for meals with friends because we are afraid of surprise glucose spikes after meals. This self-isolation affects our social life and compounds with many factors that affect our overall mental wellbeing and diabetes burnout.

How does the Pizza Effect impact our blood glucose levels?

Simply put, the delay in fat metabolism causes this increase in blood glucose. "Simple carbs," like in the bread and sauce, are quickly converted to glucose and sent into our bloodstream.

Of course, this means our Dexcom picks the readings up very quickly. But cheese, toppings, and other fats take much longer to convert to glucose, and these high-fat ingredients hit us later on.

It's the same with other foods, like chocolate, with high fat and carb components.

Alas, it is much more complex than this.

Slow-release carbs like Oats can take a bit longer to affect your blood glucose levels, and several factors affect the rate of fat metabolism into glucose.

Hang on: what is metabolism?

Briefly, metabolism is transforming the energy in food from one form to another. For example, thousands of microscopic enzymes, most of which come from your pancreas, will disassemble a potato you've eaten into its chemical components.

These chemical components retain energy (calories) in their molecular bonds, the "glue" that keeps particles together. The components are then re-assembled into Glucose molecules through a process known as the Krebs Cycle.

You can imagine a Glucose molecule as a storage box filled with molecular bonds and jam-packed with energy.

Fat metabolism processes are slower & more complex than Carbohydrate metabolism processes. There is no significant benefit to exploring the nuances of fat vs. carb metabolic processes, so we'll skip that for now.

Once generated, these glucose molecules will enter your bloodstream. You'll know this when they start appearing on your LibreLink or Dexcom apps.

So, what factors affect the conversion of fat to glucose?

1. Temperature; cold food is more resistant to enzymatic breakdown than hot food, so it can take longer to metabolize.
2. Type of food and portion sizes: Enzymes can only metabolize what they can reach. If the fat you've eaten is mixed in with lots of carbs, pastry, etc., it will be partially obscured from contact with digestive enzymes for a while. It can only be metabolized once these digestive enzymes break through that food to reach the inner fat.
3. You: Different people have different metabolic rates, different heart rates, blood pressures, and lots more. No one metabolizes a pizza the same as another person, so the timings are always unique to you. But, they should be broadly similar to others.
4. Your medical history: Some of us take medications, like powerful painkillers, that drastically affect our gut. Some of us have had our gall bladder removed, and these can all affect gut activity and fat metabolism rates.

How do carbohydrates affect our blood glucose levels?

This is a massive topic, but vital to understanding the Pizza Effect. Simply, this is where we start to regret ordering a "deep pan" pizza. All that extra bread gets transformed into a lot of glucose. Carb molecules are much smaller than fat molecules and are converted to glucose much more quickly.

That's why you've never seen a hypoglycaemia treatment with fat in it - it just wouldn't work.

Like our Treat That Hypo range of sweets, you want rapidly-absorbed, pure sugar, because time is critical. We keep a 2kg bag of Fizzy Super Mix at home, so we've got enough hypo treatments for the whole year (we never remember to keep enough juice in the house).

How do I evaluate a meal to beat the Pizza Effect?

Let's break down a Meat Feast pizza together. We'll add Jalapenos to it because we live on the wild side, and a bucket of spinach to illustrate a point again.

1. Bread - Carbs, fast glucose absorption, although not as fast as the sauce.
2. Cheese - Some carbs for early absorption but lots of fat for the second wave of glucose absorption
3. Pepperoni - No carbs, but a decent amount of fat
4. Sausage - More carbs than you would've thought! But mostly fat.
5. Jalapenos - Barely any carbs, no fat, pure fire.
6. Onion - Maybe one carb?
7. Bucket of spinach - our digestive enzymes have a lot of work to munch through this, so there will be a delay in the metabolism of any shielded fats.
8. Chicken - No fat, no carbs.
9. Chilli Oil - Basically pure fat; cooking oils are a secret saboteur. They taste incredible, but you should always be on the lookout for excess oils. Beware restaurants that use copious amounts.
10. The tomato sauce - there's a lot of it, and it's just sugar.

Can people with type one diabetes eat cake?

Absolutely! We're people before patients, and we love cake. We made a post on this. Cake is a textbook example because it's entirely made of dense fats and simple sugars.

Can people with type one diabetes eat chocolate?

Yes, we can eat anything. Once we know about the Pizza Effect, these foods become much less scary. You could call it the Chocolate Effect, the Cake Effect, or the "Impact of Macro-Nutrient Metabolism on Blood Glucose Levels."

Can people with type one diabetes eat Avocado?

Most definitely. Avocado is full of "good fats." It's usually eaten with bread or other simple carbs, so it should cause an initial blood glucose spike and a second one later.

Can people with type one diabetes eat pizza?

You already know the answer to that. However, you don't have to wade into a huge deep-pan combo pizza. Why not make a pizza on a tortilla wrap, or try a cauliflower pizza?

Type One Diabetes & the Pizza Effect won't hold you back

Ultimately, we can eat whatever we like as long as we plan for the meal and our individual diabetes needs into account. We can ask the waiter, check the labels, and give ourselves an idea of when the second wave of fat-derived glucose will hit our bloodstream.

If this article helped you, please share it with your friends or post it on Instagram (you can follow us here). Together, we can prevent the stress and frustration that so many of us go through daily.

You can support us by checking out our new Chocolate Cake Patch, Pizza Patch, and Pizza Stickers to protect and decorate your Dexcom G6, Dexcom G7, Freestyle Libre, Omnipod, and many other devices. You can browse our other 270+ patch designs here and see the devices we support here.