Background: The main regulators of body weight are food intake and energy expenditure. Hunger and satiation are important factors of food intake regulation, whereas resting metabolic rate (RMR) is the main determinant of energy expenditure. The pathophysiology of obesity is associated with changes in food intake and energy expenditure; however, their evolution throughout the lifespan of adult with obesity has not been studied simultaneously. Methods: This is a cross-sectional study of patients with obesity aged 19 to 70 years grouped by decades. We assessed hunger using 100-mm visual analog scales (VAS) 4 hours after a 320kcal breakfast, satiation using calories to fullness (CTF) in an ad libitum meal, and RMR by indirect calorimetry. We studied the effect age on these three parameters using an ANCOVA model that included age category by decades, sex, and body mass index (BMI) as covariates corrected by Dunnett's Test. We chose patients aged 19 to 29 years as control group. Results: We included 470 patients (mean SD age 42.111 years, 78% females, BMI 39.17.2). Patients were distributed in the following age groups: 19-29 years (n=70; BMI 37.6 6.4); 30-39 years (n=140; BMI 39.57.4); 40-49 years (n=132; BMI 39.78.0); 50-59 years (n=94; BMI 38.76.3); 60-69 years (n=34; BMI 37.8 6.6). Hunger was significantly different among groups (p=0.003) with a decrease on hunger levels of 13.6 mm (SE 5.3; p=0.03) in older patients (60 to 69 years) vs. controls. CTF differed significantly across groups (p<0.001) with older patients eating 163.7 kcal less (standard error SE 60.2; p=0.02) vs. controls. RMR was significantly different among groups (p<0.001) with 241.9 kcal per day (SE 55.7; p<.001) less in older patients vs. controls. Conclusion: We noticed a downward trend in food intake and energy expenditure, especially among older adults. These shifts offer information on human obesity and aging and should be considered when developing treatments for people of all ages.