Circadian rhythms, the body’s 24-hour cycles of biological, hormonal, and behavioral patterns, modulate a wide array of physiological processes, including the body’s production of hormones that regulate hunger, metabolism, sleep, and others. A new study suggests that circadian rhythms influence body weight by impairing lipid oxidation – the burning of fat.

The small study, which was conducted in two sessions, involved six healthy adults between the ages of 51 and 63 years old whose BMIs were between 22.2 and 33.4 (normal to obese). During the first session, the participants received three meals per day: breakfast (700 calories), lunch (600 calories), and dinner (1,000 calories). The second session differed in that instead of receiving breakfast, the participants received a late-night (10 PM) snack (700 calories). The overnight fast was approximately 14 hours, regardless of whether the participants ate breakfast or the late evening snack.

The authors of the study monitored the participants' metabolism in a whole-room respiratory chamber during the two sessions, which lasted 56 hours each. They found that eating a late-night snack rather than an isocaloric breakfast markedly altered the participants' capacity to burn fat, and this shift in metabolism was driven by circadian rhythm-regulated metabolic patterns. These findings suggest that late-night eating may drive body fat accumulation and subsequent increased risk for metabolic disorders such as type 2 diabetes.

• Link to full study.

• Learn more about the role of meal timing and cancer risk in this clip featuring Dr. Ruth Patterson.