Adherence

Obese individuals significantly underestimate their caloric intake and overestimate their physical activity levels when self-reporting, leading to a discrepancy between reported and actual energy expenditure and intake.

If you are obese, your memory of what you ate and how much you exercised is likely inaccurate. You probably eat more and move less than you think. Relying on self-reported logs for weight loss will likely fail because the baseline data is wrong. Use objective tracking methods (like doubly labeled water for research or calibrated devices for clinical use) if precise energy balance is required.