Timing of food intake predicts weight loss effectiveness.
Level 3 - non-randomized controlled study
Prospective observational cohort of participants undergoing a dietary intervention, grouped by self-selected meal timing
PubMed 23357955 · doi:10.1038/ijo.2012.229
What was done
A 20-week prospective study evaluated 420 adults (49.5% female; mean age 42 ± 11 years; mean BMI 31.4 ± 5.4 kg/m²) undergoing a weight-loss treatment in a Mediterranean population. Participants were divided into early eaters (51%) and late eaters (49%) based on whether they consumed their main daily meal (lunch) before or after 15:00 hours. Researchers assessed weight loss progression, dietary intake and composition, estimated energy expenditure, appetite hormones, sleep duration, chronotype, and CLOCK genetic variants.
What was found
Late eaters lost significantly less weight and had a slower weight-loss rate over the 20-week period than early eaters (P = 0.002). Total energy intake, dietary macronutrient composition, estimated energy expenditure, appetite hormones, and sleep duration did not differ significantly between groups. Late eaters were more frequently evening chronotypes, consumed smaller breakfasts, and skipped breakfast more often (P < 0.05). The minor C allele of CLOCK rs4580704 was more prevalent in late eaters (P = 0.041), but chronotype, sleep duration, and CLOCK genotypes were not independently associated with weight loss (all P > 0.05). Absolute kilograms of weight lost were not reported in the abstract.
Why it matters
This study provides human evidence that the timing of food intake may influence weight-loss success independently of total caloric intake and macronutrient distribution.
Limits
Meal timing was self-selected rather than randomized, leaving room for confounding lifestyle factors. Findings reflect a Mediterranean population where lunch is typically the largest meal, which may not generalize to cultures with different eating patterns. Absolute weight loss numbers and confidence intervals were omitted from the abstract.