Navigating the post-meal rollercoaster

Dr Paula Diab shares valuable tips for keeping blood glucose spikes in-check to avoid the post-meal rollercoaster.

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Over nearly 20 years of assisting people managing their diabetes, I’m always humbled by how much there is to know about the disease. Not too long ago, I thought that if you could master the art of counting carbohydrates, then dosing insulin would be simple. 1 unit of insulin for every 15g of carbohydrates. 1 slice of toast = 15g of carbohydrates. What could be easier?

But if practicing medicine has taught me nothing else, it is that medicine is an art as much as it is a science. Seemingly simple maths does not always add up.

In listening to patients, I began to realise that they too were finding that this simple maths didn’t always work and that eating a burger with a side salad as a starter would sometimes work out better than eating just the burger alone. And then I had the opportunity to attend an international conference where I attended a lecture on macro-sequencing and the puzzle pieces slowly started to fit together.

One of the latest buzzwords or phrases in diabetes management is Time in Range (TIR). This refers to the overall time during the day that you spend within a particular target range. This range can depend upon your circumstances but is generally between 3.9 – 10.0mmol/L (70-180mg/dL).

If you are able to spend 70% or more of your time within this range, your risk of complications and overall prognosis in diabetes will be greatly improved. Studies have shown that kidney and eye disease are accelerated with greater post-meal peaks as well as these rises being an independent risk factor for developing cardiovascular disease.

Matching the action of insulin

Short-term glucose control is also negatively affected by these post-meal peaks which manifests in a decrease of energy, cognition (thinking) difficulties, mood swings and other physical and emotional abilities are affected.

As we then struggle to get the readings back into range, a common problem is that of overcompensating and causing what clinicians refer to as a rebound-low. A key component of remaining in range is therefore being able to manage your glucose levels after meal times and not just monitoring your fasting glucose levels early in the morning.

Keeping your glucose levels to remain in the target range with as little fluctuation as possible. In fact, if you are trying to get your glucose levels closer to that magic number of an HbA1c of 7%, managing your after-meal peaks is going to be all the more important.

It is normal to have fluctuations in glucose levels throughout the day even for people who don’t have diabetes. However, if the peak of the rise is too high or lasts too long, this may have adverse effects on your health. The idea in diabetes is to match the action of insulin with the consumption and digestion of carbohydrates.

Measuring and targets

Medicine is an art as well as a science. So, whilst most people will experience a peak about 60 – 90 minutes after starting their meal, this may vary from person to person and depending upon the meal eaten.

The next conundrum occurs when looking at what your targets should be. General guidelines suggest a post-meal peak of <10mmol/L (180mg/dL); however, this may also vary. Elderly patients or those with multiple co-morbidities may be encouraged to set their targets slightly higher to avoid the disastrous consequences of hypoglycaemia whilst pregnant women will be encouraged to have a much tighter range and not allow their post-meal peak to rise above 7.8mmol/L (140mg/dL) in order to prevent unnecessary damage to the foetus.

Peak management

  1. Selecting the correct insulin

Very often people think that all rapid-acting insulins are the same. The reality is that whilst most people (particularly with Type 2 diabetes) don’t notice a significant difference between insulin aspart or glulisine, for example, other people do react very differently.

There are also newer ultra-rapid insulins that will act even quicker as well as different formulations of insulin (inhaled insulin, not yet available in South Africa) that also work much quicker.

  1. Injection technique

The manner in which you inject insulin can also affect the way it’s absorbed and how quickly and efficiently it acts. Injected insulin works much faster when the injection site is warmed. This can be done by rubbing the site before injecting, exercising the muscle near the site or immersing the site in warm water.

In practical terms, your insulin may be absorbed quicker after a warm bath, after a run or on a warm summer’s day. Injecting directly into the muscle (anterior thigh or arm) is not usually indicated but if you are wanting insulin to work very quickly in the case of diabetic ketoacidosis (DKA) or treating a very high glucose level, this will certainly make a difference.

Remember that working quicker or faster doesn’t mean working for a longer time which will be discussed later.

  1. Pre-bolusing

Some people may have heard about the concept of pre-bolusing or injecting insulin prior to a meal. This can have a significant impact on squashing the peak that occurs after a meal, but you do need to be careful.

The aim is to get the insulin into your body and working at its maximum at the same time as your meal peaks. The exact timing of this will depend on multiple factors as medicine is an art, as well as a science.

High glycaemic index (GI) foods will peak quicker and therefore may require a bolus 15 – 30 minutes before the meal whilst lower GI foods may digest better when the insulin is given at the start of the meal. Higher pre-meal glucose values may respond better when mealtime boluses are more pronounced whereas lower glucose levels may benefit from insulin taken during or even after the meal.

  1. Other medications

The effect of insulin may be enhanced by other hormones, such as GLP-1 receptor agonists. These delay gastric emptying and keep carbohydrates from raising the blood glucose levels too quickly after meals.

Another drug, pramlintide (not available in South Africa) also helps to reduce appetite and squash the post-meal secretion of anti-insulin hormones in the body. Both of these medications will result in much more stable glucose levels and smaller peaks.

These are the pharmaceutical ways in which you can squash that post-meal peak but there are also quite smart manoeuvres you can try with simple lifestyle adjustments that will also have a significant impact.

Lifestyle adjustments

  1. Glycaemic index

As mentioned previously, lower-GI foods (pasta, beans, legumes) will digest slower and therefore have a flatter peak if you measure the glucose response.

Higher-GI foods (bread, cereal, potatoes, rice) are converted into glucose more quickly and therefore will tend to give a higher and more pronounced peak.

In addition to balancing the timing of your insulin, try to balance your meals with a combination of carbohydrates so that you do not only get a quick peak and then feel hungry again soon afterwards.

  1. Acidity

The addition of acidity to food has also been shown to reduce the post-meal spike. In practical terms, this can be in the form of sourdough bread as opposed to regular flour bread; adding vinegar or even tomato sauce as a condiment.

  1. Food sequencing

The order in which you eat your food has also been shown to be important in maintaining stable glucose levels. Having a salad or vegetables prior to your main meal will allow time for your digestive enzymes to be secreted so that when you eat your carbohydrates, your body is optimally-primed to digest these foods.

Fats will slow down the absorption of carbohydrates in the body. The most typical example is that of a cheesy pizza – very often insulin is given in split doses in this case to match the peak of the carbohydrate as well as the delayed peak of the fat in the cheese.

Proteins will also slow down the absorption of food in the body and contribute to satiety (fullness) therefore reducing the overall glucose load.

As always, a healthy balanced meal is recommended so experiment with your favourite meals and see what the impact can be on your post-meal peaks.

  1. Splitting meals

Other suggestions are to split the meal and have a portion of the meal 30 – 60 minutes after the initial meal. This is particularly useful if you are to embark on a large gourmet feast. The longer you take to eat the food, the more time your body has to digest it.

Even smaller meals can be broken down in this way by having a cup of coffee prior to breakfast and then eating the bowl of cereal and milk a while later.

Those who like to have a mid-morning or mid-afternoon snack may consider removing a serving of fruit from breakfast or lunch and having it between meals. In this way, the body is presented with smaller loads of carbohydrates more consistently which will certainly assist in more regular blood glucose levels. Please speak to your clinician about how to dose insulin if you are going to split your meals in this way.

  1. Exercise

If ever there was a solution to almost all problems, it is that of physical activity. Being active after eating will reduce post-meal peaks by slowing down absorption of glucose into the bloodstream. The body also uses the glucose consumed and actually becomes more sensitive to insulin as well. Ten to twenty minutes of mild activity (walk, household chores, etc.) is usually adequate.  

  1. Prevent hypoglycaemia

We’ve spoken often about the dangers of hypoglycaemia but one of the most overlooked problems is the vicious cycle that it creates. The body responds to low glucose levels by doing everything it can to counteract this potentially lethal situation. It empties the stomach quicker, food is digested quicker and blood glucose levels rise more rapidly. In addition, counter-regulatory hormones are released that stimulate glucose production in the liver. The end result – blood glucose levels peak and it becomes difficult to lower them again.

Take-home lessons

Its highly possible that by now your blood glucose levels have dropped, due to all the mental agility, or sky-rocketed, due to the stress response elicited by the body by reading all this information. Perhaps, they’re perfectly stable with no change at all.

If you take away one thing, remember that medicine is an art as well as a science. Sometimes, what looks like simple maths is actually a complex interplay of numerous different factors with even more unexpected outcomes.

Another good point to remember is to be alert to new ideas and thinking and constantly try to improve your knowledge and understanding of diabetes. What worked for the last 20 years, may not be the most ideal way to manage your diabetes and sometimes change is necessary and even helpful.

Experiment with your medication and food and find out what works best for you. Read through this article slowly and carefully and try one strategy at a time and get a good idea of the impact it has on your diabetes.

Obviously, all these strategies are much easier when using a continuous glucose monitor but you can get a very good idea by testing before and two hours after each meal and then discussing your findings with your diabetes educator or diabetologist.

Treat it as an interesting puzzle and try to solve the conundrums. Even experienced clinicians are sometimes forced to go back to the drawing board and ask for assistance. Managing the post-meal rollercoaster very often requires time, lots of trials and testing and a great team-effort.

Dr Paula Diab


Dr Paula Diab is a diabetologist at Atrium Lifestyle Centre and is an extra-ordinary lecturer, Dept of Family Medicine, University of Pretoria.

Header image by FreePik


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