Fats and Proteins – To bolus or not to bolus? That is the question.

There is a lot of information and uncertainty in the world of Type 1 Diabetes and whether to bolus for protein and fats or not. I, for one, am often unsure how to take these into account when my 14 year old daughter needs to bolus for a meal.

Recently, I became aware of current research that is being undertaken by Dr Kirstie Bell and other highly esteemed medical professionals at the Charles Perkins Centre, University of Sydney.  The resumes of those leading the charge in relation to researching the effects of Fats and Protein are long and cover all facets of Type 1 Diabetes specialisation.

As a parent to a child with T1D, what I can say for certain is that different foods affect my daughter in different ways. I am yet, however, to determine in my own mind, how do I account for fats and protein? So, I thought I would go direct to the source of this research and contact Dr Bell. She was very kind with her time and provided the following findings from the research to date.

What effect does fat and protein have on blood glucose levels?

Carbohydrates have the biggest effect on blood glucose levels but our research, and others, is showing fat and protein can also have a substantial impact.  This has really been highlighted by the Type 1 Diabetes community, who for years have been seeing this on their glucose monitors and, more recently, on their continuous glucose monitoring traces.

The blood glucose response to fat and protein looks different to the response to carbohydrates.  While carbs tend to start raising glucose levels fairly quickly after a meal, the response to fat and protein is much more delayed. In the first 2-3 hours after a meal, fat and protein can slow down the digestion and release of carbs into the bloodstream and lead to a lower early glucose response.

After about 2-3 hours though, fat and protein start exerting their own effect, leading to high blood glucose levels that can stick around for 6 hours or more.  The effect of fat is only obvious when eaten with carbs but protein can have an effect whether it’s eaten with carbs (e.g. spaghetti bolognese) or without (for example, steak & salad).  However, you need more protein in a meal to see an effect if there are no carbs.  What’s more, fat and protein have an additive effect, meaning that their effects on blood glucose levels are added when eaten together, causing an even bigger response overall.

It’s important to remember that just as everyone has differences in sensitivity to carbohydrate (i.e. you need a personalised insulin: carbohydrate ratio), sensitivity to fat and protein will also be individual.  Some people will really notice a difference after these meals while others won’t.  It also depends on what you usually eat – if you normally eat a consistent amount of fat and protein throughout the week, then even if your ‘usual’ is high, chances are that your long-acting or basal insulin has been tailored to account for some of the effects of fat and protein already.  However, for those out-of-the-ordinary meals e.g. fish & chips on the beach, pizza night or a breakfast cook-up, you might need a different insulin dosing approach to keep blood glucose levels in check.

How to dose insulin for fat and protein?

Just as your response to fat and protein is going to be individualised – so is the insulin dosing solution.  No one size will fit everyone perfectly and it might take some experimentation to find what works for you.  We do know some general ‘rules’ though:

  • Insulin can’t all be dosed upfront – as fat and protein have a delayed effect and can reduce glucose levels in the first 2-3 hours, simply dosing extra insulin at the time of the meal can contribute to a higher risk of hypoglycemia in this time. It also means there will be less insulin working when fat and protein start raising blood glucose levels 2-3 hours later.
  • If you use an insulin pump – try using a dual-wave (also called a combination wave), so some of the insulin is dosed upfront as usual and the remainder is dosed over about 2 hours.
  • If you use insulin injections, you may need some extra insulin 1-2 hours after the meal.


iBolus Graph


We hope this clarifies things for you but please remember that individual circumstances vary greatly in relation to Type 1 Diabetes and it is important to work with your Clinical team to get the most effective outcome for your needs.

We will be staying in contact with Dr Bell and can’t wait to see more of the research findings. Further information can be found at http://www.ibolus4t1d.com.

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