New research in mice suggests that meal order matters for blood sugar. Researchers at Kyoto University and collaborators gave fasting mice olive oil either before or after glucose, and found that fat first blunted the usual spike in blood glucose. Fat-before-glucose also slowed gastric emptying and raised early levels of the hormones GIP, GLP-1, and even glucagon—a hormone usually associated with raising blood sugar. The benefit held in mice with type 2 diabetes and severe insulin deficiency.
Exactly how the effect worked was not obvious. Blocking GLP-1 or glucagon signaling alone did not remove the benefit; blocking both weakened it, suggesting the two hormones cooperate. Surgical interruption of the vagus nerves below the diaphragm also altered the response, indicating that the nervous system is part of the mechanism. Together, these findings point to a coordinated interaction among digestive hormones, pancreatic signals, and neural communication.
The study was done in mice, so it does not prove the same response occurs in people. However, previous clinical studies in humans have already shown that eating vegetables, protein, or fat before carbohydrates can limit post-meal blood sugar increases. As the researchers note, meal sequencing is appealing because it changes how a meal is eaten rather than requiring people to avoid entire food groups.