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Protein, Fat and BGs

STUDENT CONTRIBUTOR: Michael Sheng | Nutrition & Food, Ryerson University

March 30, 2021

While most people living with diabetes pay special attention to the amount of insulin they take based on the amount of carbohydrates on their plate, recent research has shown that fat and protein intake can also have an impact on blood sugar levels.

How do fat and protein impact blood sugar?

When it comes to protein’s impact on blood sugar... it’s complicated. There are conflicting studies providing varied results, depending on whether protein is eaten with carbohydrates or on its own. For example, 30 grams of protein eaten with CHO can affect blood glucose, but more than 75 grams of protein eaten on its own may be required to have any affect on blood glucose if eaten alone. However, scientific evidence supports a 30% increase in insulin results in significantly lower blood sugar levels after a high-protein meal (50g protein, 30g carbohydrate, low-fat breakfast drink).

For people with diabetes, when protein is digested it forms glucose. That glucose is then stored as glycogen in the liver, making it difficult to estimate how much actually enters the bloodstream and impacts blood sugar levels. However, there is evidence that larger amounts of protein at one meal results in an increase in production of the glucagon hormone, translating to a slow rise in blood sugar that can occur 3-5 hours after eating. Because protein has the ability to act as a ‘buffer’ - meaning it keeps your digestive system busy digesting protein - it leads to overall slower carbohydrate digestion and a slower, delayed increase in blood sugar.

Unlike protein, scientists have - for the most part - figured out how fat effects blood sugar. Evidence shows that fat slows stomach emptying and increases insulin resistance, leading to a delayed increase in blood sugar. However - unlike protein - fat is not converted to glucose, so the impact of fat on blood sugar relates back to increased insulin resistance as opposed to an increase of glucose in the bloodstream. The magnitude of fat's effect on insulin resistance is individualized, with some people having a strong rise in insulin resistance after consuming fat, while others have a less of a response. You can test it our for yourself by consuming small amounts of fat and measuring blood sugar levels 2 hours after eating to see how your body responds to fat. This method of testing allows people managing diabetes with insulin to adjust meal time doses accordingly.

How do I manage my blood sugar with fat and protein?

There are many ways to calculate an extended bolus. The Warsaw School Program Method - outlined below - takes into account the effects of fats and protein on blood sugar. As an example, we’ll look at one serving of Planters Nuts and Chocolate Trail Mix.

1, Calculate calories from fat and protein

  • Protein has 4 calories/gram, while fat has 9 calories/gram. Calories from fat and protein can be calculated with the equation, (Grams of protein)x4 + (Grams of fat)x9. In the example of Planters Trail Mix, Calories from fat and protein = (5g of protein)x4 + (11g of fat)x9 = 119 calories from fat and protein.

2, Calculate fat-protein units (FPUs)

To calculate a fat+protein:carbohydrate equivalent, we need to calculate fat-protein units (FPUs), which are equal to calories from fat and protein100kcal/FPU. In our example, that would be 119 calories from fat and protein100kcal/FPU = 1.19 FPU.

3. Calculate extended bolus time frame. This can be calculated with the following guidelines.

  • for 1 FPU, program the extended bolus over 3 hours

  • for 2 FPUs, program the extended bolus over 4 hours

  • for 3 FPUs, program the extended bolus over 5 hours

  • for 4 FPUs, program the extended bolus over 8 hours

For this step, round your FPU value to the nearest whole number. In this case, we round 1.19 FPU = 1 FPU, or 3 hours extended bolus.

4.Calculate carb:insulin equivalent

  • 1 FPU is equivalent to 10g carbohydrates worth of insulin requirement. Each person has their own carbohydrate:insulin ratio. This is known through trial and error, or through your health care professional. Once you have your ratio, convert FPU to grams of carbohydrate equivalents and calculate insulin levels. Be sure to use your FPU value from step 2, not the rounded value from step 3. In our example, this would be 1.19FPUx10=11.9g carbohydrates, assuming a 1:15 ratio, 11.9g carbohydrates15 = 0.79U of insulin delivered over 3 hours.

Another method factors in the percent increase using a dual bolus. When a person with diabetes is having a meal that includes more than 40 grams of fat and more than 25 grams of protein with a carbohydrate choice, the insulin dose required - calculated using an insulin to carb ratio (I:CR) - would be increased by 30-35%.

  • using an insulin pump: deliver 50% of this new dose (usual dose + increase) as a normal pre-meal bolus and 50% as square or extended wave over 2-2.5 hours

  • giving multiple daily injections (MDI): give 50% of this new dose (usual dose + increase) as pre-meal bolus, then a 50% post-meal bolus 1-1.5 hours after the meal.

Assess the affect on blood sugars and adjust the dose split as required:

  • the pre-meal bolus vs post-meal BG ratio (60:40, 50:50, 40:60, 30:70 ...)


  • the duration of post-meal insulin delivery (3, 4, or 6 hours, etc.)

For people with diabetes following a diet of less than 100 grams of carbohydrate per day, the New Zealand Method for Low Carbohydrate eating patterns method can be applied.

  • Calculate bolus for carbohydrates by using the usual I:CR (e.g., 1 unit for 10g CHO)

  • For protein dosing, multiply I:CRx2 (e.g., 1 unit: for 20g PRO)

So, if Mary was eating a meal with 15g of carbohydrate and 60g of protein using a carb ratio of 1:10, she would calculate her dose this way:

  • carbohydrate = 15g/10 (I:CR) = 1.5 units

  • plus protein = 60g/20 (ICR x 2) = 3 units

  • for a total dose of 4.5 units

*No insulin is given for fat in this method

**This method is only appropriate for low carbohydrate diets.

As with any dietary plan, the method outlined above is not a ‘one size fits all’ fix for protein and fats with diabetes. Everyone’s diabetes impacts them differently, and you should speak with a physician or registered dietitian to make sure this is right for you. It should also be noted that this method is not considered best practice by Clinical Practice Guidelines set by the Canadian Diabetes Association, so according to Canadian health professionals, this method may be risky.

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