What the glucose spike warriors aren’t telling you

What is a Glucose Spike?

When we eat, our body breaks down food into glucose, a form of energy that enters our bloodstream. In response, the hormone insulin is released to help move glucose from the blood into our cells, where it’s used for energy.

A blood sugar spike occurs when this glucose enters the bloodstream quickly or in large amounts (like after a meal or snack), causing a temporary rise in blood sugar levels. The extent of a spike depends on how fast glucose is absorbed, how much enters the blood, and how long it stays elevated.

What Causes a Blood Sugar Spike?

While many people believe only carbohydrates impact blood sugar, glucose spikes can be influenced by:

Since blood sugar responses can vary hourly due to these factors, tracking glucose spikes from specific foods isn’t always useful—unless advised by a doctor or if you have diabetes. Your blood sugar response to a banana today may be completely different from how your body reacts to the same banana next week or even later that same day!

Do High Glucose Spikes Mean Poor Health?

A higher blood sugar spike does not mean a food is unhealthy.

Some nutrient-dense, whole foods (like certain fruits and vegetables) may cause a larger glucose spike because their natural sugars are easily digestible. However, this does not make them “bad.” In fact, research shows that fruit intake can actually improve fasting blood glucose levels in those with insulin resistance (3). 

On the other hand, some processed or less nutritious foods may cause a lower glucose spike simply because they contain more fat, which slows digestion. For example, a chocolate bar might lead to a smaller blood sugar spike than a piece of fruit but that obviously doesn’t mean the chocolate is the healthier choice.

The missing puzzle piece 

Many of the glucose spike “experts” online leave out a key part of the puzzle: the cause of insulin resistance.

Insulin resistance is when your body stops reacting in an appropriate way to these blood sugar spikes meaning that blood sugar can stay high for too long. This is what happens in type 2 diabetes. 

How to improve blood sugar control? 

Maybe you’ve been told by a GP that your HbA1c levels are too high or that you are pre-diabetic and so you want to improve your blood sugar control, or you want to become more insulin sensitive.

Rather than focusing only on these individual glucose spikes, it’s important to address what’s actually causing the insulin resistance. One key factor in developing insulin resistance is an over consumption of saturated fat (4).

This is why the advice to swap foods that may cause a quicker blood sugar spike (like oat milk) for high-fat alternatives that spike less but are higher in saturated fat (like full-fat milk) isn’t the best approach. While a food may have a lower immediate impact on blood sugar, its long-term effect on insulin resistance matters more.

Another common swap recommended by “glucose hackers” online is replacing a sweet pastry, like a pain au chocolat, with a savory ham croissant. In reality, both are high in saturated fat and aren’t great for blood sugar control. If anything, the ham croissant may be worse; processed meats are not only classified as Group 1 carcinogens, but they have also been linked to an increased risk of diabetes (5). So if you’re going to have a pastry, just have the one that you want, knowing that it’s a treat to be enjoyed and not something you’re eating for your health.