Eating breakfast after 9 a.m. increases the risk of developing type 2 diabetes by 59% compared to people who eat breakfast before 8 a.m. This is the main conclusion of a study in which ISGlobal, an institution supported by “la Caixa” Foundation, took part and which followed more than 100,000 participants in a French cohort. The results show that we can reduce the risk of diabetes not only by changing what we eat, but also when we eat it.
Type 2 diabetes is associated with modifiable risk factors, such as an unhealthy diet, physical inactivity and smoking. But another factor may be important: the time at which we eat. “We know that meal timing plays a key role in regulating circadian rhythms and glucose and lipid control, but few studies have investigated the relationship between meal timing or fasting and type 2 diabetes,” says Anna Palomar-Cros, ISGlobal researcher and first author of the study.
In this study, a team from ISGlobal joined at team from INSERM in France to investigate the association between meal frequency and timing and the incidence of type 2 diabetes among 103,312 adults (79% women) from the French NutriNet-Santé cohort. Participants filled in online dietary records of what they ate and drank over a 24-hour period on 3 non-consecutive days, as well as the timing of their meals. The research team averaged the dietary records for the first two years of follow-up and assessed the participants’ health over the following years (an average of seven years).
Early breakfast, early dinner
There were 963 new cases of type 2 diabetes during the study. The risk of developing the disease was significantly higher in the group of people who regularly ate breakfast after 9 a.m., compared to those who ate breakfast before 8 am. “Biologically, this makes sense, as skipping breakfast is known to affect glucose and lipid control, as well as insulin levels,” explains Palomar-Cros. “This is consistent with two meta-analyses that conclude that skipping breakfast increases the risk of type 2 diabetes,” she adds.
The research team also found that a late dinner (after 10 pm) seemed to increase the risk, while eating more frequently (about five times a day) was associated with a lower disease incidence. In contrast, prolonged fasting is only beneficial if it is done by having an early breakfast (before 8am) and an early dinner.
“Our results suggest that a first meal before 8 am and a last meal before 7 pm may help reduce the incidence of type 2 diabetes,” concludes Manolis Kogevinas, ISGlobal researcher and co-author of the study. In fact, the same ISGlobal team had already provided evidence on the association between an early dinner and a lower risk of breast or prostate cancer.
Taken together, these results consolidate the use of chrononutrition (i.e. the association between diet, circadian rhythms and health) to prevent type 2 diabetes and other chronic diseases.