Circadian rhythms and gastrointestinal hormone-related appetite regulation.

Purpose of review: Circadian biology influences the gastrointestinal system as exemplified by hormonal patterns that modulate appetite. Indeed, people tend to get hungrier towards the later parts of the day. How misalignment of our circadian biology with behavioral factors (i.e. diet, exercise, sleep, etc.) influences obesity related disease has been an area of intense recent investigation.

Recent findings: The gastrointestinal hormones (e.g. ghrelin, glucagon-like polypeptide-1, glucose dependent insulinotrophic peptide, peptide tyrosine-tyrosine, and insulin) play unique roles across the 24-h cycle in fostering anticipatory responses that promote desires to eat while concurrently responding to environmental stimuli. A persons chronotype has emerged as a target area since it provides a metric of circadian biology interacting with environmental factors and affects all people. In fact, later chronotypes tend to be at higher risk for obesity, due to in part, alterations in gastrointestinal hormones (e.g. GIP, insulin) that align with behavioral observations of greater food intake and desires to eat fatty/sweet foods later in the day.

Summary: Changes in gastrointestinal hormones across the 24-h cycle impact obesity risk when misalignment of our circadian biology occurs with behavioral cycles. Better understanding how chronotype modulates appetite may enable personalized prescription of exercise, diet and/or medication to foster reduced chronic disease risk.