The order in which you eat different foods may have a surprising effect on blood sugar levels. Research in mice suggests that consuming fat before carbohydrates can reduce the sharp rise in blood sugar that typically follows a meal. The findings also reveal how hormones and nerve signals work together to influence this response.
Keeping blood sugar from rising too high after eating is an important part of diabetes management. Previous clinical studies have shown that eating vegetables, protein, or fat before carbohydrates can help limit these increases. This suggests that changing the sequence of foods during a meal could offer a practical, sustainable way to improve blood sugar control without eliminating entire food groups.
Scientists have generally explained this effect through two main mechanisms. The first is slower gastric emptying, which means food moves from the stomach into the small intestine more gradually. The second involves increased release of hormones called incretins, including GLP-1, which help the body regulate blood sugar.
However, researchers have not fully understood how hormones produced by the gut and pancreas interact with the nervous system to produce these effects. To investigate, an international research team examined how consuming fat before or after glucose influences blood sugar, hormone activity, and the speed at which the stomach empties.
“Our group has long been interested in practical dietary approaches that people can continue in everyday life,” says corresponding author Daisuke Yabe of Kyoto University. “Meal-sequencing is appealing because it merely changes how a meal is eaten rather than requiring people to avoid entire food groups.”
Testing How Olive Oil Changes Blood Sugar Levels
The researchers conducted a series of experiments in mice to determine whether the timing of fat consumption affected how the body processed glucose.
After an overnight fast, the mice were assigned to three groups. One group received water followed by glucose. A second group was given olive oil, followed 15 minutes later by glucose. The third group received glucose first, with olive oil administered 15 minutes afterward.
The scientists then measured blood glucose levels and several hormones involved in blood sugar regulation, including insulin, glucagon, GIP, and GLP-1. Glucagon is normally associated with increasing blood sugar, while GIP and GLP-1 help regulate glucose levels after eating.
To determine how quickly material was leaving the stomach, the researchers also administered acetaminophen, a common pain reliever. By measuring how much of the drug appeared in the bloodstream after oral administration, they could estimate the rate of gastric emptying.
The team extended the experiments to additional groups of mice, including animals with type 2 diabetes and others that lacked the receptor needed to respond to GLP-1.
They also performed experiments that blocked glucagon or GLP-1 signaling, surgically interrupted the vagus nerves below the diaphragm on both sides, and examined whether different dietary fats produced similar results. The vagus nerve is an important communication pathway between the brain and digestive system, helping coordinate functions such as digestion and hormone release.
Eating Fat First Slows Blood Sugar Spikes
The results showed a clear difference depending on when the mice received olive oil.
When olive oil was given before glucose, the initial rise in blood sugar was smaller than when the oil was administered afterward. The earlier fat intake also slowed gastric emptying, delaying the movement of glucose from the stomach into the intestine.
At the same time, consuming fat before glucose stimulated an early increase in several hormones, including glucagon, GIP, and GLP-1.
Importantly, these effects were also observed in mice with type 2 diabetes and severe insulin deficiency. This suggested that the response could still function even when normal insulin regulation was significantly impaired.
A Surprising Role for a Blood Sugar Hormone
One of the most unexpected findings involved glucagon, a hormone generally known for raising blood sugar by stimulating the liver to release stored glucose.
The researchers discovered that blocking glucagon signaling alone did not eliminate the blood sugar lowering effect of consuming olive oil before glucose. Blocking GLP-1 signaling by itself also failed to remove the benefit.
However, when both signaling pathways were blocked simultaneously, the beneficial effect was reduced.
This finding suggests that glucagon and GLP-1 work together as part of a more complex system that helps moderate blood sugar after fat is consumed before carbohydrates. It also reveals that glucagon, despite its familiar role in increasing blood sugar, can contribute to a response that ultimately limits the rise in glucose after eating.
The vagus nerve experiments provided another important clue. When the researchers interrupted these nerve pathways, the results suggested that communication through the vagus nerve also contributes to the body’s response to nutrient order.
Together, these findings point to a coordinated interaction between digestive hormones, pancreatic signals, and the nervous system.
Could Changing Meal Order Help Manage Diabetes?
The findings offer a clearer biological explanation for why eating fat before carbohydrates may help reduce blood sugar spikes. Rather than relying on a single hormone or digestive process, the effect appears to involve multiple systems working together to control how quickly glucose enters the intestine.
This could have practical implications for diabetes management. Adjusting the order in which foods are eaten is relatively simple and may be easier to maintain than diets that require avoiding particular food groups.
However, the experiments were conducted in mice, and the same effects have not yet been established in humans through this research. Additional clinical studies will be needed to determine whether the mechanisms identified in the experiments can be used to improve blood sugar regulation in people with or without diabetes.
“Our findings suggest that the order in which nutrients reach the gut can engage a coordinated hormone-nerve response that changes how quickly the stomach delivers glucose to the intestine,” says Yabe.
