In trying to gain or maintain a healthy weight, how much you eat may actually matter less than the timing of your meals, according to a surprising study conducted by researchers from Brigham Women's Hospital, Tufts University, the University of Murcia, and published in the International Journal of Obesity.
"This is the first large-scale prospective study to demonstrate that the timing of meals predicts weight-loss effectiveness," senior author Frank Scheer said. "Our results [suggest] that the timing of large meals could be an important factor in a weight loss program."
The study was conducted on 420 overweight people who were categorized as either early eaters or late eaters, depending upon the time of day at which they preferred to eat their large meal (because the study was conducted in Spain, the largest meal of the day was lunch). Anyone who ate lunch before 3 p.m. was classified as an early eaters, while anyone who ate lunch after 3 p.m. was classified as a late eater. The average participant consumed 40 percent of their daily calories at the large meal.
All participants were enrolled in a 20-week weight-loss treatment program. At the end of the program, the early eaters had lost significantly more weight than the late eaters, and had lost weight more quickly. Late eaters also demonstrated a lower insulin sensitivity, indicating that they were at higher risk for diabetes than the early eaters.
The researchers found no difference between calorie intake, energy expenditure, sleep duration, or levels of the appetite-related hormones leptin and ghrelin between the early and the late eaters. This suggested that the timing of the meal was, in and of itself, a significant factor influencing weight loss.