Meal timing helps suppress appetite
Restricting the timing of food intake facilitates weight loss not by altering energy expenditure but by regulating appetite, according to a recent study.
“Aligning food intake with circadian rhythms may therefore be a powerful strategy for reducing appetite and losing weight,” said researchers. “The subset of meal-timing interventions that involve intermittent fasting, such as time-restricted feeding, may confer additional metabolic advantages by improving metabolic flexibility and increasing 24-hour fat oxidation.”
Eleven overweight adults (mean age, 32±7 years; seven males) were included in the randomized, crossover, isocaloric, controlled feeding trial. After the early time-restricted feeding (eTRF) condition, appetite between 11:00 AM and 5:00 PM was significantly suppressed (p≤0.05), while all five indicators were increased at bedtime (10:30 PM; p≤0.007). [Obesity 2019;doi:10.1002/oby.22518]
The five appetite indicators used were hunger, desire to eat, capacity to eat, fullness and stomach fullness. None were significantly altered by eTRF at breakfast (8:00 AM; p=0.09 for capacity to eat, p≥0.39 for the other) or in the middle of the evening (8:00 PM; p≥0.27).
Overall, the eTRF regimen suppressed the daily amplitudes in hunger (change, –10±3 mm; p=0.006) and desire to eat (change, –9±5; p=0.09), while also reducing the mean desire to eat (change, 5±2 mm; p=0.08) and increasing mean stomach fullness (change, 3±2 mm; p=0.06) and fullness (change, 3±2 mm; p=0.10).
At the same time, eTRF elicited a significant dip in morning concentrations of active ghrelin (change, –43±15 pg/mL; p=0.009), leptin (change, –4±1 ng/mL; p=0.01) and glucagon-like peptide 1 (change, –0.8±0.3 pmol/mL; p=0.008). Ghrelin was likewise reduced during evenings (change, –22±12 pg/mL; p=0.09) while peptide YY3-36 levels were increased (PYY; change, 17±6 pg/mL; p=0.02).
“We found that eTRF lowered mean values of the hunger hormone ghrelin (mostly in the morning) as well as increased levels of the satiety hormone PYY in the middle of the evening,” corroborating the patterns obtained when using appetite indicators, said researchers.
“Surprisingly and paradoxically, eTRF reduced swings in hunger (i.e., reduced the diurnal amplitude of hunger), making hunger levels more even-keeled throughout the day, which may reduce overeating or binge eating,” they noted.
Despite such changes in appetite and satiety markers, researchers observed no significant effect of eTRF on energy expenditure. While there was a daytime excess in energy expenditure after food restriction (change, 56±15 kcal per 12 hours; p=0.003), this was offset by a drop in expenditure during nighttime (change, –46±6 kcal per 12 hours; p<0.0001).
Overall, the net effect of eTRF on energy expenditure failed to reach statistical significance (p=0.55).
“[O]ur data suggest that meal-timing interventions facilitate weight loss primarily by suppressing appetite,” said researchers. “Although we were not powered to detect differences in 24-hour energy expenditure as small as approximately 20 to 40 kcal/d, such small differences are considered clinically insignificant.”
“Further research is needed to determine the effects of meal timing on energy and fat metabolism,” they added.