For People with Type 1 Diabetes

Why does Fat and Protein affect BGL's?

Fat and protein have a relatively small affect on glucose levels in people who don't have diabetes.  However, both fat and protein have been shown to have a big impact on blood glucose levels in people with type 1 diabetes. But why?


The reason is due to the lack of enough insulin.  Insulin is best known for its role in moving glucose (from carbohydrate) from the bloodstream and into the cells. But did you know that insulin is also needed to transport fatty acids (from fat) and amino acids (from protein) into the cells too?  Carbohydrate, fat and protein all tell the body to secrete insulin when you eat them.  People without diabetes are able to make this extra insulin and so don't see much affect on their blood glucose levels.  But people with type 1 diabetes can't  produce insulin - so they can see the rise in their blood glucose levels.

Did you know Fat and Protein  in Foods can also affect your Blood Glucose Levels?

Adding Fat & Protein Increases BGL

What Can I do?

Managing type 1 diabetes is a tough gig and we don't yet know exactly how insulin needs to be adjusted for different meals.  So, rather than 'counting' every gram of fat and protein (as with carbohydrate counting), we have gotten together with the other key researchers in this field to come up with these top tips to identify your problem-meals and how to tackle them.

1. Healthy Eating is still Important

As much as many of us would love to tuck into our favourite junk foods as often as we liked, with no health consequences, healthy eating will always be a foundation of good health - diabetes or not. Healthy eating and regular meals and snacks (opposed to grazing) also help improve consistency in BGL patterns - which in turn makes it easier to dose insulin.

2. Brush up on Carb Counting

While it might seem irrelevant to fat and protein dosing - brushing up on your carb counting skills is another really important step.  Carbs are the number one nutrient affecting BGL and it's easy for portion size estimates and carb contents to get fuzzy with time. This is also a good time to identify any challenges you're having (such as forgetting mealtime doses) and working out strategies to overcome these.  Missed doses will have a much bigger impact on your BGLs and HbA1c than fat or protein can.

3. Identify problematic meals
Once your healthy eating plan and insulin therapy has been optimised, it should be much clearer to see how high protein or fat meals affect your BGL.

Rather than introducing insulin adjustments for every meal containing protein or fat, it may be easier to start out identifying problematic meals, i.e. those high fat or protein meals that are the most difficult to dose for.  This might be family pizza night, fish & chips on the beach, a pub meal with the boys or a cafe big breakfast.  

4. Consider alternative meals or adjust insulin dose

One option is to choose an alternative, healthier option - this might mean swapping your fried fish for grilled so it fits better with your overall health goals.  However, healthy eating doesn't mean never having those 'treat' foods.  So, the second option is to adjust the insulin dose to better match what your body needs for that meal.  

The evidence suggests that insulin doses may need to be substantially increased but given everyone is so different, we suggest working closely with your team and starting with small adjustments. 
Insulin needs to be delivered either using a dual wave with an insulin pump or as a second injection ~1hr after starting the meal.  This will help reduce the risk of hypo early on and ensure the insulin is available later when the body needs it most. 

What Affect Does Fat & Protein have on BGL?

What Affect Does Fat & Protein have on BGL's?

Fat and protein don't affect blood glucose levels the same way that carbohydrates do.

Carbohydrates are digested into glucose and generally cause blood glucose levels to start rising soon after the meal, peaking after 1-1.5 hours.  International guidelines recommend that the blood glucose level returns to target within 2-3 hours.

Fat and protein affect BGL differently to carbohydrate. Both fat and protein have a delayed impact and their affects aren't seen until 1.5 to 2 hours after the start of the meal.  This delay might be due to the nutrients, particularly dietary fat, slowing down the movement of food through the stomach.  As a result, the carbohydrate, fat and protein take longer to be digested and absorbed.  The result is a lower blood glucose response in the first 2-3 hours after the meal, the BGL  peaking later and an increased risk of having a hypo.

However, things tend to get more interesting from about 3 hours after the meal onwards.  Meals high in fat and/or protein can lead to high blood glucose levels in this time, lasting at least 5-6 hours and probably longer!  The graph below shows the average BGL for 10 adults with type 1 diabetes when they had a meal high in both fat and protein (cheese pizza) compared to a meal that was low in both fat and protein (same pizza base but with no cheese).  After 6 hours, the BGL was 5.5 mmol/L higher with the fat & protein meal!

It's important to remember everyone is different though, and your body might not respond the same way to fat or protein as someone else with type 1 diabetes.  Just like everyone needs a different amount of insulin for carbohydrate (known as your insulin: carbohydrate ratio if you flexible insulin therapy), everyone likely needs a different amount of insulin for fat and protein.  

When making any adjustments, it is important to get to know your body,    work closely with your diabetes team    and monitor your BGL to see if that adjustment worked for you!​