The aim was to test the difference in glycemic variability after meal consumption during intermittent fasting and the usual diet.

Healthy participants were recruited for this crossover study aiming to determine the difference in glycemic variability after meal consumption while practicing intermittent fasting and the usual diet. Prior to the protocol assignment, participants were followed for 3 days - they were instructed to maintain their usual sleep pattern, level of physical activity and diet. Control of dietary pattern was conducted by using the 3-day food diary. Day zero was preparation day for the protocol (Intermittent fasting or Control diet) when all participants received individualized 3-day diet plan. Each protocol lasted 3 days with a 7-day washout period. Each protocol consisted of 3 meals per day, each providing a third of the total energy requirement. Control diet protocol was set at 12 hours eating/12 hours fasting, and Intermittent fasting protocol 6 hours eating/18 hours fasting. Blood glucose was measured at zero, 15, 30, 45 and 90 minutes after meal consumption. Before breakfast, blood glucose was measured also at minus 5 minutes prior meal consumption.

Inclusion Criteria:

• Body Mass Index in the range between 18.5 and 29.9 kg/m^2
• stable sleep pattern (going to bed between 21:30h and midnight)
• for women: regular menstrual cycle lasting between 21 and 35 days, with average bleeding time 2 to 6 days

Exclusion Criteria:

• Body Mass Index below 18.5 or above 29.9 kg/m^2
• irregular sleeping pattern
• work in nightshift
• high intensity workout routine
• irregular dietary patterns (e.g. skipping meals)
• regularly fasting for more than 15 hours per day
• diagnosis of diabetes (or other conditions related to glycemic disorders)
• hypertension or other cardiovascular disease
• neurologic conditions
• disease affecting metabolism (like liver, kidney, thyroid or lung)
• use of medications for glycemia, hypertension, steroids, adrenergic stimulators, laxatives or supplements affecting glycemia, circadian rhythm, sleep or metabolism in general

All the results will be published (as journal manuscript) and freely accessible to all interested parties. Also, interested parties can contact investigators for any details regarding the study and results (for example if individual data is required for a meta-analysis).