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Beyond Diet: What Causes Blood Sugar Spikes?

Unpacking the relationship between food, stress, sleep, and exercise when it comes to regulating blood sugar.

Key Takeaways:
  • Eating sugary, processed foods, especially on an empty stomach, will cause blood sugar spikes.
  • Stress and lack of sleep can lead to higher blood sugar.
  • Physical activity can temporarily raise blood sugar but is overall a net positive.
  • The paleo diet is one of the most beneficial ways of eating for long-term blood sugar maintenance.
  • Studies support a “carbs-last” approach as a strategy to help regulate blood sugar in non-diabetics—eat good quality protein, fat, and veggies first to mitigate the blood sugar spike
  • New research supports a connection between high blood sugar and dementia.


As we gain more and more knowledge about the role and impact of blood sugar levels on health and wellness, we learn that physical health conditions are only the beginning. We’ve been taught that high blood sugar (hyperglycemia) can lead to type 2 diabetes and the host of health problems that come with it (blurred vision, blood vessel and nerve damage, kidney disease, heart disease, etc). 

But we now know that prolonged high blood sugar can affect brain health and cognition as well. In fact, research now shows that prolonged high blood sugar can also lead to cognitive issues, including Alzheimer’s and dementia. Alzheimer’s disease is now considered “type 3 diabetes” [1]

A diet high in processed foods and simple sugars will cause blood sugar spikes and stress your pancreas, liver, and kidneys, in addition to increasing insulin resistance, which can lead to type 2 diabetes. But diet alone isn’t the only lifestyle factor responsible for helping you maintain healthy blood sugar levels.

Understanding your day-to-day activities, dietary habits, stressors, gut health, and sleep quality can help you determine what leads to the biggest blood sugar spikes for you. While every individual is different (some are more affected than others by one or some lifestyle factors), it’s important to have a clear picture of your own health status in order to make good decisions.

Let’s go over the nuts and bolts of maintaining healthy blood glucose levels and also take a look at the latest research on the relationship between blood sugar and brain health.

What Causes Blood Sugar Spikes?

Diet isn’t the only factor that can affect blood sugar. And even the question of diet is more complex than simply what you put in your mouth. Like much of what we look at when it comes to health and wellbeing, the devil is in the details—the what, the when, the how much, and the context. Some of the factors that impact blood sugar levels include:

  • Diet: when, what, and how much you eat [2]
  • Physical activity: type, duration, intensity, and timing [2, 3]
  • Stress levels: intensity and duration [2, 3]
  • Illness: both acute and chronic [3]
  • Menstruation: hormonal fluctuations at various times in the month [3]
  • Metabolic conditions, like the insulin sensitivity of your muscles [2]
  • Sleep: quality and quantity [4]
  • Medications that may affect your metabolism, gut microbial composition, or other bodily functions that impact organ health [3]
  • Alcohol consumption: timing, quantity, and in the presence or absence of food [3]

Each of these factors can have a greater or lesser impact on blood sugar levels, depending on the choices you make. Let’s start with diet.

Which Foods Spike Your Blood Sugar (and Some Simple Hacks)

We know that highly processed, sugary foods (those high in simple carbohydrates and high on the glycemic index) can cause a rapid spike in blood sugar. This means candy, cake, ice cream, pastries, cookies, white bread, white rice, pasta, etc. We also know that the timing of those foods—both the time of day you eat them and whether or not you’re eating them on an empty stomach—will further influence the spike [2].

While nutrient-poor, highly processed, sugary foods are best avoided altogether, in the real world, we have birthday parties, holidays, and other celebrations where it’s fair to want a piece of cake or a scoop of ice cream every once in a while. If you know you’ll be doing that, put your meal-planning hat on and think ahead.

You’ll want to eat some good quality protein, fat, and veggies first to mitigate the blood sugar spike. Studies support a “carbs-last” approach as a strategy to help regulate blood sugar in non-diabetics [5].

The veggies contain fiber, which will slow down the absorption of sugar into your bloodstream, and protein and fat before or at the start of a meal will reduce the speed of food leaving the stomach, priming insulin to be released once glucose hits the system [6].

If you’re in the habit of starting your day with a bowl of cereal, a slice of toast, or a pastry, it’s time to switch that up for a more protein-rich breakfast. This will help keep your blood sugar stable throughout the day, as well as keep you full for longer. Taking a daily probiotic may also help [7].

The Paleo Diet

The Paleo Diet—a generally higher-protein diet that focuses on whole, unprocessed foods and eliminates nearly all grains and legumes—has been studied for its effects on both diabetes management and also reducing blood sugar spikes in healthy people. When compared to other healthy diets like the Mediterranean diet and the American Diabetes Association diet, the long-term effects (2 years or more) of the Paleo diet seem to be more beneficial to blood sugar regulation [8].

None of the three healthy diets studied seemed to have much, if any, impact on blood sugar levels in the short term, but they all similarly improved weight, body mass index (BMI), and waist size, especially in the short term. All three diets improved total and LDL cholesterol and triglycerides in the short term, but the Paleo diet performed best. It was also better than the other two healthy diets at reducing fasting blood sugar, fasting insulin, insulin resistance, and HbA1c (an inflammatory marker) in the short term [8].

In another study comparing the Paleo diet with the Mediterranean diet, diabetes diet, American Diabetes Association diet, Dutch Health Council Diet, Nordic diet, and standard heart-healthy diet, the Paleo diet was better in the long term (two years or more) than the others at reducing:

  • Insulin resistance
  • Fasting insulin
  • Total cholesterol
  • Triglycerides
  • LDL cholesterol
  • Blood pressure
  • C-reactive protein

However, the Paleo diet was about the same as most of the other diets in its effects on fasting blood sugar, HbA1c, and HDL cholesterol [9].

High-Protein Diets

While the Paleo diet can be high-protein, it doesn’t necessarily have to be. Studies comparing high-protein diets (not specifically paleo) to high-carb diets showed that high-protein diets actually stimulate the production of glucose-lowering hormones. 

In a small randomized controlled trial, obese men and women with prediabetes were given either a high-protein or high-carb diet to follow for 6 months. 100% of those on the high-protein diet had remission of prediabetes, compared to 33% of those on the high-carb diet. Those on the high-protein diet had better levels of glucose-lowering hormones than those on the high-carb diet [10].

Based on these findings in the shorter term and the long-term benefits of the Paleo diet, it stands to reason that a high-protein Paleo diet would be the right approach for the best and most effective way to keep high blood sugar levels and other important biomarkers under control.

Physical Activity

The American Diabetes Association recommends moderate daily exercise to bring blood sugar levels down while exercising [11]. However, intense aerobic exercise and weight lifting can cause blood sugar to rise slightly until your muscles are exhausted [11, 12]. While this spike shouldn’t be a cause for concern, one way to mitigate this spike is by ensuring that you’re properly hydrated before and during strenuous activity. I interviewed Kara Collier on the topic of glucose spikes during a hard workout in a fruitful discussion about continuous glucose monitoring. She helped to reassure that the overall effect of exercise is a net positive on blood sugar regulation, even if it temporarily rises during the activity itself. 

She explained that steady-state exercise AND intense exercise can improve both your glucose sensitivity and your overall health and well-being. Strength training, specifically, is beneficial because the more lean muscle mass you have, the more sensitive your cells will be to insulin (which is a critical part of blood sugar regulation) [12].

It’s not a bad idea to consider purchasing a continuous glucose monitor if you’re concerned about your blood sugar. It can get expensive if your health insurance doesn’t cover the purchase, but keeping a food journal and examining the data that one of these little machines can provide, even if only for a few months, could help you identify the foods, activities, and stressors that cause blood sugar spikes for you.

Stress, Illness, Sleep, and Gut Health

These factors are grouped together because they are unquestionably interrelated. It’s difficult to talk about the impact of poor sleep without discussing how poor sleep impacts your gut microbiota. Stress and gut health are also linked, as well as stress and poor sleep quality. We also know that a massive part of your immune system resides in your gut microbiome, so the topic of illness and immunity is gut-related as well.


In response to a stressor, your body releases the stress hormone cortisol to prepare your body for fight or flight. Over time, the chronic release of cortisol can lead to insulin resistance, which is a precursor to diabetes [13].

How we handle stress (resilience), develop restorative habits, and reduce anxiety will impact our metabolic functions and ability to properly regulate blood sugar. Meditation, reducing anxiety, and reducing inflammatory inputs can be part of a positive feedback loop in the mind-body connection.


Poor sleep quality and quantity (but especially quantity) appears to raise blood sugar levels, according to research. In a study seeking to understand the relationship between various stages of sleep and insulin response/blood sugar levels, researchers found slow-wave sleep (deep sleep) was associated with better metabolic and psychological function [14]. 

Another study found that short sleep (inadequate quantity) was associated with a greater risk of metabolic syndrome, obesity, high blood pressure, and high blood sugar. Interestingly, long sleep (getting too much sleep) also posed a risk in all the above areas except high blood sugar [15].

This area of research is still in its early stages, and the potentially confounding factors associated with long sleep (such as depression) weren’t mentioned. More work needs to be done to better understand both the role of each stage of sleep as well as how each stage affects various biomarkers.

Good Stress

All this being said, there’s such a thing as “good stress.” Good stress is also known as eustress or hormetic stress. This type of stress represents a positive challenge—the “sweet spot” for stress on your body and mind. While physical hormetic stress has been shown to temporarily raise blood sugar levels, high-intensity exercise can improve blood sugar control after a meal and over time (2, 12, 16, 17, 18).

Alcohol Consumption

Alcohol consumption is the perfect segue into the intersection of blood sugar and brain health. That’s because overconsumption of alcohol has been implicated in the onset of Alzheimer’s disease [19]. First, let’s talk about alcohol’s impact on blood sugar.

While the inclusion of alcohol with a healthy meal doesn’t seem to have much, if any, effect on blood sugar for non-diabetics, chronic alcohol consumption, overconsumption, consumption on an empty stomach, and consumption while dehydrated can actually lead to low blood sugar (hypoglycemia)  [20, 21, 22].

Dangerous hypoglycemia can also result from a diabetic (both type 1 diabetes and type 2) consuming alcohol either on an empty stomach or in conjunction with their diabetes meds [23].

It might be tempting to conclude that alcohol’s ability to lower blood sugar would mean that if a person with diabetes sprung for a sugary cocktail, the two inputs would balance out to a stable blood sugar level. But unfortunately, that’s not the case. The body absorbs liquid sugars too quickly to prevent the drop in blood sugar that might result from the alcohol hours after the drink was consumed [23]. 

The best way to consume alcohol is to keep the amount truly moderate (one 12-oz beer, 5 oz glass of wine, or 1.5 oz shot of hard liquor), skip the sugary additives, and eat a balanced meal with your beverage [23].

Brain Health and Blood Sugar

Metabolic syndrome is a collection of symptoms that has been shown to lead to cardiovascular disease, insulin resistance, and type 2 diabetes. These serious chronic illnesses can result in many downstream complications, including loss of blood flow to the brain. The symptoms include [24]:

  • Large waistline: A waist that’s 40 inches or larger in men and 35 inches or larger in women
  • High triglycerides: Triglyceride levels of at least 150 mg/deciliter of blood
  • Low HDL (“good”) cholesterol: HDL cholesterol of 40 mg/dL or less in men and 50 mg/dL or less in women
  • High blood glucose: Fasting blood glucose levels of 100 mg/dL or greater
  • High blood pressure: Systolic blood pressure of 130 mmHg or higher and/or diastolic blood pressure of 85 mmHg or higher

In order to be diagnosed with metabolic syndrome you need to have at least three of the symptoms above, but simply having high blood glucose can contribute to a higher risk of developing dementia and worsening dementia-related symptoms [25, 26].

Just like cardiovascular disease, certain types of cancer, and a host of other chronic illnesses and conditions, there exists a genetic tendency toward high blood sugar. If you have a family history of high blood sugar or diabetes, it’s especially important that you work with a healthcare provider to keep your blood sugar levels under control.

A 2020 study looking at genetic data for associations between blood glucose levels and the risk of dementia, Alzheimer’s disease, and vascular dementia found that lifelong high blood glucose was causally related to a 140% greater risk of developing dementia, but not Alzheimer’s or vascular dementia [25].

A systematic review of 46 observational studies found that high blood glucose may worsen disease outcomes related to dementia, but wasn’t able to make a solid determination on whether high blood sugar increases the risk of impaired cognitive function or developing dementia [26].

While this area of study is in its early stages, what we do know is that the brain runs on glucose. There is a rapid growth in scientific research pointing toward insulin deficiency (not enough insulin) and insulin resistance (too much insulin floating around and not being used to neutralize blood glucose properly) as mediators of neurodegeneration related to Alzheimer’s. But the research is inconclusive when scientists attempt to find a link between Alzheimer’s and type 2 diabetes, metabolic syndrome, and obesity.

That being said, experimental brain diabetes has been successfully treated with insulin sensitizer agents (diabetes medications) in the lab, so this area of research is really promising [1].

Keeping Blood Sugar Spikes at Bay

The lay of the land when it comes to what causes blood sugar spikes and how to keep them at bay is all about diet, lifestyle, and awareness. The amount of sugar you eat is an obvious factor, but when you eat it might not have been before reading this article. Eat carbohydrates and sugars at the end of your meals, stick to whole foods when you can, and consider trying the paleo diet.

Exercise regularly, and stay hydrated when you do it. Building lean muscle mass is a net positive for blood sugar regulation, even if you spike your blood sugar during exercise. Getting enough sleep, mitigating the stress in your life, and taking a probiotic will all lend a hand in keeping your blood sugar stable.

If you’re concerned about your blood sugar and would like some guidance on how to make effective changes, we’d love to help you. Reach out to our clinic to become a patient.

The Ruscio Institute has developed a range of high-quality formulations to help our patients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you.

➕ References

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