Participants followed a four-week regimen of ad libitum food intake from 08:00 to 18:00, followed by a 14-hour fasting period until 08:00 the next day, while maintaining habitual physical activity and sleep patterns.

Ad libitum food intake from 08:00 to 18:00, followed by fasting from 18:00 to 08:00 for four weeks. Outside the eating window, water and limited amounts (1-2 servings) of very low-calorie items (e.g., tea, diet soft drinks, coffee, chewing gum <4 kcal/serving) were permitted. The intervention focused exclusively on the timing of food intake and did not impose restrictions on the quantity or type of foods consumed.

Participants arrived at the laboratory between 08:30 and 09:00. An antecubital catheter was placed, and five blood samples were collected at fasting (0 min) and at 30, 60, 90, and 120 minutes after consuming the test meal. The test meal consisted of 100 g of S-Core FLEX Compact Protein powder (40 g carbohydrate, 29 g protein, 19 g fat) dissolved in 250 mL of water, providing 475 kcal.

Participants wore a wireless skin temperature sensor (Thermochron iButton® DS1921-F5) on the palmar surface of the wrist of the non-dominant hand for 2 consecutive days. Circadian rhythmicity was analyzed using Cosinor analysis, which applies the least-squares method to fit the chronobiological data to cosine functions with predetermined periods of 12 and 24 hours.