Glucose spikes
(10-12 minute read)
Blood glucose spikes: one of the more talked-about areas of wellness, that some claim to tackle most of our health concerns. Based off the premise that blood glucose spikes are inherently bad, controlling these spikes have been presented as a solution to weight gain, aging and hormone imbalances.
Clinically, blood glucose spikes were once a concern confined to people only living with diabetes, whose bodies cannot regulate blood sugar effectively on their own. Now, this physiological response is something positioned for even those with normal blood glucose regulation to monitor.
What are blood glucose spikes?
When we eat, the body breaks down food into glucose which enters the bloodstream. Blood glucose levels rise, and the pancreas releases a hormone called insulin. Insulin allows glucose to enter the cells of the body to be converted into energy or stored as glycogen for later use. Glucose is the body's preferred energy source, and when dietary intake is insufficient, the body will convert protein into glucose. This occurs during fasting, prolonged exercise, or during significant calorie restriction. A rise in blood glucose after eating is a normal physiological response.¹
Different foods cause different sized rises in blood glucose levels. As carbohydrates are fundamentally composed of sugar molecules, they produce larger rises compared to protein or fat. The type of carbohydrate also matters; simple carbohydrates are rapidly broken down into glucose and produce sharper rises, while complex carbohydrates take longer to digest and produce a more blunted response.²
The size of a glucose spike produced by the same food also varies considerably from person to person. Two people can eat the same foods and produce very different responses, determined largely by their gut microbiome composition, insulin sensitivity, and broader lifestyle factors such as sleep and stress.³
Are large blood glucose spikes bad for us?
In people living with diabetes or impaired glucose tolerance, the answer is well established. These populations of people cannot produce sufficient insulin, or cannot respond to it effectively, to bring glucose spikes back to normal levels. Over time, this repeated glucose elevation causes serious harm to the cardiovascular system and organs.⁴ In healthy individuals, however, the picture is considerably less clear. Research more consistently links harm not to how high glucose levels rise after a meal, but to how long they stay elevated. Prolonged elevation is far more characteristic of insulin resistance and type 2 diabetes than of healthy metabolic function. A healthy body is built to handle post-meal rises; glucose levels rise, then return to baseline.⁵ In metabolically healthy people, the evidence that reducing these peaks translates to any meaningful health benefit remains limited.⁶
Why are we suddenly paying attention to them?
Continuous glucose monitors (CGMs), small sensors that sit on the back of the arm and track blood glucose levels in real time, were originally developed for people living with diabetes.⁷ In recent years, they have become available to the wider population and targeted to healthy people to optimise their overall health.⁸ This has given people visibility into a normal physiological process that they previously did not have. Watching glucose levels rise and fall in response to different foods, and linking those changes to health outcomes is compelling. Consequently, a growing perception has emerged that monitoring and minimising glucose spikes can optimise health, accompanied by a plethora of advice on how to actively reduce these peaks.⁹
Is there research to support the use of CGMs in healthy people?
There is optimism surrounding the future use of CGMs in healthy populations, but the current evidence for meaningful health benefits remains limited and largely unproven outside diabetes care. Systematic reviews provide a high-quality summary of the available research on a specific question. In this area, they generally conclude that there is currently insufficient high-quality evidence to support that monitoring blood glucose levels improves health outcomes in healthy individuals without diabetes.¹⁰
One review of 25 studies found that people using CGMs spent around 7% more time within their recommended blood glucose range. However, results varied considerably between studies, and there was no clear evidence that these changes translated into meaningful health benefits. Participants using CGMs lost an average of 0.7 kg, but this was not statistically significant. Some evidence suggested that CGMs influenced food choices, although there is currently no convincing evidence that they improve overall diet quality. Notably, much of the available research included people with type 2 diabetes, reflecting the current literature.¹¹
In another systematic review, fluctuations in blood glucose levels throughout the day were examined in people without diabetes. These fluctuations are referred to as glycaemic variability (GV), which describes the degree of variation in blood glucose levels over time. GV was higher in people with impaired glucose regulation and was associated with reduced insulin secretion. However, there was no consistent relationship between GV and other markers of cardiometabolic health, including body fat, blood pressure, blood lipid levels, or markers of cellular stress. Some evidence linked higher GV with more severe coronary artery disease and increased cardiovascular risk, although this was limited to people who already had established coronary artery disease.¹²
A further systematic review explored whether CGMs could help prevent cardiovascular disease among people without diabetes. Some studies reported short-term improvements in glucose patterns following dietary or physical activity interventions. However, the evidence was highly variable, with many studies limited by small sample sizes and short follow-up periods. While CGMs may help people understand how lifestyle factors influence glucose levels, there is currently insufficient evidence that they improve long-term cardiovascular or metabolic health.¹³
Overall, current evidence does not support the routine use of CGMs to improve health in metabolically healthy people. Although these devices provide valuable insight into individual glucose responses, research has yet to demonstrate that reducing normal post-meal glucose spikes results in meaningful long-term health benefits. Larger, long-term studies are needed before such claims can be made.
Insight into blood glucose spikes has prompted a myriad of advice which provides guidance on how to lower glucose spikes
Avoiding ‘naked carbs’
‘Naked carbs’ is a concept that describes eating carbohydrates on their own rather than as part of a mixed meal. A mixed meal contains carbohydrates alongside protein, fat, and fibre. Research consistently supports choosing mixed meals over carbohydrate-only meals, as they generally produce more moderate glucose responses and greater satiety.¹⁴
A review and analysis of 154 studies found that adding protein to a carbohydrate-containing meal consistently lowered post-meal blood sugar spikes in people without diabetes, with a clear dose-dependent effect: the more protein added, the greater the reduction. This was accompanied by a larger insulin response, suggesting the body handled the glucose more effectively with protein, than when carbohydrates were eaten alone.¹⁵
Similar effects are observed when fat is included in a meal. Dietary fat can slow the rate at which food leaves the stomach, leading to a more gradual rise in blood glucose after eating. This effect is thought to be partly related to slower gastric emptying and the action of incretin hormones such as GLP-1 and GIP.¹⁶
Gastric emptying: the process where food moves from the stomach into the small intestine for nutrient absorption into the bloodstream. When this process slows, food is released more gradually, resulting in a smaller rise in blood glucose.
Incretin hormones: such as GLP-1 and GIP, help regulate blood sugar levels by supporting insulin release in response to food intake. GLP-1 also slows gastric emptying. As a result, the body produces an enhanced insulin response to meals, helping improve blood sugar control after eating.
Whilst extensive research supports that mixed meals acutely reduce insulin spikes, it is not proven that reducing these spikes through avoiding ‘naked carbs’ translates to meaningful long-term health benefits in metabolically healthy individuals. The robust set of research which favours balanced meals containing fats, fibre, protein, and carbohydrates, is attributed to from other reasons outside of blood sugar regulation; most notably those governing satiety and appetite regulation.¹⁷
Strong evidence shows that meals combining carbohydrates, protein, fibre, and fat support satiety. Protein has the most pronounced effect, increasing fullness by raising the satiety hormones GLP-1, PYY, and CCK, while reducing the hunger hormone ghrelin.¹⁸ Fibre and fat affect appetite in different ways: fibre slows digestion and increases gastric expansion, while fat slows gastric emptying and stimulates satiety hormones, allowing energy to enter the bloodstream more gradually.¹⁹ This plays a key role in maintaining a healthy weight and is widely encouraged by Nutritionists and Dietitians.²⁰
Eat foods in the right order
Eating foods in a particular order has also attracted growing interest. Studies by Dr. Alpana Shukla’s research group based at Weill Cornell Medicine in New York suggest that eating vegetables or protein before carbohydrates lowers the rise in blood sugar, compared with eating carbohydrates first.²¹ As with mixed meals, this effect is thought to result from slower gastric emptying, increased release of incretin hormones, and more gradual glucose absorption into the bloodstream.¹⁴ This mechanism was also demonstrated in earlier work that found eating fat 30 minutes before a carbohydrate meal slowed gastric emptying, reduced the rise in blood sugar, and shifted incretin hormone levels (lowering GIP and raising GLP-1) in people with type 2 diabetes.²²
The magnitude of these effects results in only modest and short-term changes, and there is currently no evidence that they translate into meaningful long-term health benefits in healthy populations. Compared with mixed meals, food-ordering strategies have substantially less supporting evidence, as balanced meals offer broader benefits, particularly in terms of satiety.
Movement after eating
It is very well established that walking after eating reduces blood sugar spikes. This is because contracting muscles increase glucose uptake and storage in muscle tissues. A classic physiological study of exercise metabolism demonstrated that when muscles are active, they take up significantly more glucose from the bloodstream and channel it into glycogen synthesis in skeletal muscle.²³ The glucose uptake into muscle tissue was shown to occur without a rise in insulin levels, because the process is driven by muscle contractions.²⁴
Modern research have confirmed this on real-world human studies, with one study showing that walking for 30 minutes after eating helped lower and improve blood sugar responses, regardless of the meal consumed, for example high-carb or mixed macronutrient. This finding was observed in young-healthy individuals.²⁵ Further research found that the closer exercise was performed to the meal, the greater the reduction in post-meal glucose responses.²⁶
While walking after meals is often discussed in the context of reducing post-meal glucose spikes, the underlying physiological benefits are far broader than a single measurement. Regular walking after meals helps the body to clear sugar from the bloodstream more effectively, reduces how much insulin is required to process a meal, and improves how efficiently muscles use energy. Post-meal walking is a useful everyday tool for managing blood sugar, as its effects can be replicated in real-life settings across different meals, not just observed in controlled laboratory conditions.²⁷ This repeated pattern over time may support improved insulin sensitivity and metabolic flexibility, meaning the body becomes more efficient at metabolising both carbohydrates and fats for fuel based on availability and demand.²⁸
Pre-meal vinegar
Apple cider vinegar (ACV) has a long-standing reputation within the health industry for supporting weight loss, reducing bloating, and more recently improving blood sugar control. ACV has been shown in multiple randomised controlled trials and meta-analyses to produce a statistically significant reduction in postprandial blood glucose and insulin responses. Systematic reviews of clinical trials report that vinegar taken before or with carbohydrate-containing meals can lower post-meal blood sugar spikes and insulin responses.²⁹ ³⁰ ³¹
While the studies referenced show a consistent effect of ACV on post-meal blood sugar control, these translate into relatively small to modest health benefits in real-life settings. A key limitation of the current literature is that many studies are short-term, use relatively small sample sizes, and focus on immediate responses to a meal, which limits how well the findings translate to long-term health outcomes in real-world settings. The benefits are also relatively small in practice compared with other lifestyle strategies, such as walking after meals. As a result, its clinical significance as a standalone strategy is limited, and claims around ACV are often stronger than what the current research evidence supports.³²
Aging by glycation
Blood glucose spikes have been acclaimed to accelerate internal and external signs of aging through a process called glycation. Glycation is a natural chemical process in which free sugars react with proteins, DNA, and fats without the involvement of enzymes, forming compounds known as Amadori products. These compounds then undergo a series of irreversible chemical changes, eventually leading to the formation of advanced glycation end products (AGEs). The glycation process leads to a loss of protein function and impaired elasticity of tissues such as blood vessels, skin, and tendons; hence why it has been connected to aging.³³
Glycation occurs at a faster rate when blood sugar levels remain consistently elevated over time. This is why the process has been associated with many of the long-term complications seen in diabetes, where accelerated metabolic aging is more commonly observed. This has been demonstrated in studies showing that long-term high blood sugar promotes the formation and accumulation of advanced glycation end products (AGEs).³⁴ ³⁵ AGEs are linked to damage in blood vessels and other tissues in people with diabetes and are thought to contribute to features of accelerated ageing over time.³⁶
Glycation occurs in all individuals, including those who are metabolically healthy, as it is a normal by-product of glucose metabolism. However, while chronic hyperglycaemia in diabetes clearly accelerates AGE formation and contributes to tissue damage, the extent to which normal post-meal glucose fluctuations in healthy individuals meaningfully drive accelerated aging is far less well established.³⁷
The evidence connecting postprandial glucose spikes to premature aging in metabolically healthy people is very limited and not directly established. In one instance, a study found a relationship between AGEs and insulin levels; however, this work does not demonstrate that AGEs cause changes to the normal aging process.³⁸ In another setting, a smaller study found that glucose variability in healthy individuals was not associated with increases in oxidative stress markers, which are often linked to biological aging processes.³⁹ Overall, given the limited evidence available, attributing glucose rises in metabolically healthy individuals to accelerated ageing appears to be overstated.
Summary
Blood glucose spikes are a normal physiological response to eating. Current research does not support that reducing the size of glucose spikes in metabolically healthy individuals results in meaningful health benefits. The most robust advice which are targeted to reduce the size of a glucose spike are less attributed to the peaks in isolation but those that have wider health benefits. Moving after eating and avoiding ‘naked carbs’, have the most well supported evidence to improve long-term overall health.
References:
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