Could changing when you eat help manage type 1 diabetes?
A small new study suggests it might. Adults with type 1 diabetes who limited eating to an eight-hour window each day improved a measure of long-term blood sugar control compared with those who followed a traditional calorie-restricted diet.
But the findings are early. Only 32 people participated, and the eating schedule did not lead to significantly greater weight loss, which was actually the main outcome researchers set out to study.
For six months, participants with type 1 diabetes and overweight or obesity were randomly assigned to one of three groups. One group ate only between noon and 8 p.m. without counting calories. Another tried to cut daily calories by 25%. A third continued eating as usual.
At the end of the study, which was published in Diabetes Care, people following the eight-hour eating window had lowered their HbA1c, a blood test that reflects average blood sugar over the previous two to three months, by about half a percentage point more than the calorie-restriction group.
Researchers did not find meaningful differences between the groups in average glucose levels or the total amount of insulin participants used.
The study also produced a less exciting result on weight.
Participants following the eight-hour schedule lost about 2.2% of their body weight over six months. But that was not significantly different from the weight change seen in either the calorie-restriction or usual-diet groups.
That matters because researchers originally designed the study primarily to see whether time-restricted eating could help people with type 1 diabetes and excess weight lose more weight than standard calorie restriction.
Instead, the more interesting signal emerged in blood sugar control.
“This is the first step to showing time-restricted eating could be a safe, potentially effective method for people with Type 1 diabetes to manage their blood sugar levels,” said senior author Krista Varady, a professor of kinesiology and nutrition at the University of Illinois Chicago.
Safety is especially important in type 1 diabetes.
People with the condition make little or no insulin and depend on insulin therapy to keep blood sugar within a safe range. Going long periods without food can complicate that balance and potentially raise the risk of blood sugar dropping too low, rising too high or, in severe cases, diabetic ketoacidosis.
In this study, the eight-hour eating window did not increase cases of severe low blood sugar, severe high blood sugar or diabetic ketoacidosis.
Still, 32 participants are far too few to establish that this approach is safe for everyone with type 1 diabetes.
The trial also enrolled a carefully selected group. Participants had type 1 diabetes along with overweight or obesity, and people with a recent history of severe hypoglycemia or certain serious medical conditions were excluded. Participants also used continuous glucose monitors during the study.
That means the results should not be taken as evidence that anyone with type 1 diabetes can safely start intermittent fasting on their own.
The study also raises a broader question about why meal timing might matter.
The eight-hour eating window did not produce significantly more weight loss and did not reduce insulin use compared with the other groups. Yet HbA1c improved compared with calorie restriction. That suggests timing itself could influence some aspects of blood sugar management, although a study this small cannot tell researchers exactly why.
Larger trials will be needed to see whether that HbA1c improvement holds up in more people, whether it lasts over time and whether it leads to meaningful health benefits.
For now, the findings offer an intriguing first look at time-restricted eating in a group that has largely been left out of intermittent-fasting research.
“Of course, this is just the first step,” Varady said. “Anyone making changes to their eating habits, especially those with diabetes, must work closely with their endocrinologist or healthcare provider to find a solution that works for them.”
The clinical trial was sponsored by the University of Illinois Chicago.