Morning ghrelin concentrations are not affected by short-term overfeeding and do not predict ad libitum food intake in humans.

BACKGROUND: Ghrelin has a short-term orexigenic effect but may also be a marker of food intake over time. We previously found an inverse association between ghrelin concentrations and food intake.
OBJECTIVES: The objectives were to determine whether the fasting plasma ghrelin concentration is related to food intake and whether the previous day's intake predicts the suppression of ghrelin.
DESIGN: Sixty-nine nondiabetic adults (40 men) aged 33 +/- 9 y were studied as inpatients at a Clinical Research Center. After 6 d of consuming a maintenance diet, the subjects self-selected their food from our vending machine system for 3 d. Total plasma ghrelin concentrations were measured every morning during the vending machine period.
RESULTS: The fasting ghrelin concentration was negatively correlated with body mass index (r = -0.31, P = 0.016) and weight (r = -0.26, P = 0.044). Mean morning ghrelin concentrations remained constant (149 +/- 59, 152 +/- 60, 148 +/- 61, and 145 +/- 59 pg/mL on days 1, 2, 3, and 4, respectively) even though the subjects overate while using the vending machines (160 +/- 42% of weight-maintenance needs). No associations were found between daily ghrelin concentrations and subsequent food intake on any day (day 1: r = -0.04, P = 0.76; day 2: r = -0.01, P = 0.95; day 3: r = -0.11, P = 0.38). Suppression of total ghrelin concentrations was not associated with the previous day's intake or with subsequent food intake.
CONCLUSION: Morning plasma ghrelin concentrations do not affect acute increases in food intake. This trial was registered at clinicaltrials.gov as NCT00342732.