Participants will receive standard nutrition education materials per institutional practice. No fasting regimen will be prescribed during immune checkpoint inhibitor (ICI) therapy.

Participants will follow a repeating cycle of approximately 12 hours of eating followed by 36 hours of fasting every other day during ICI therapy. During fasting periods, participants may consume plain coffee, sugar-free tea, sugar-free herbal tea, sugar-free chewing gum, and 1-2 cups per day of clear vegetable or meat broth (up to 500 kcal/day). The fasting intervention will begin within 1 week of ICI initiation and continue for 8 cycles of therapy (approximately 20-24 weeks).

Participants will consume all daily calories within an 8-hour eating window each day during ICI therapy, typically between 10:00 AM and 6:00 PM, with flexibility to shift the window by 1 hour earlier or later. Outside the eating window, participants may consume plain coffee, tea, herbal tea, sugar-free chewing gum, and 1-2 cups per day of clear broth. The fasting intervention will begin within 1 week of ICI initiation and continue for 8 cycles of therapy (approximately 20-24 weeks).

Participants will follow an alternate-day fasting regimen during ICI therapy consisting of approximately 12 hours of eating followed by 36 hours of fasting every other day.

Adherence will be assessed using participant-completed fasting diaries. For the time-restricted eating (TRE) arm, adherence is defined as meeting the assigned fasting window on ≥5 days per week.

For the alternate-day fasting (ADF) arm, adherence is defined as meeting fasting-day criteria on ≥5 days within each 14-day period.

Adherence will be summarized as the proportion of participants who meet the assigned regimen-specific adherence criteria during the study period.

Adverse events (AEs) and immune-related AEs (irAE) will be summarized and compared descriptively between study arms. Events will be graded according to CTCAE. The proportion of participants experiencing irAEs, including grade ≥3 irAEs, will be summarized by treatment group.