For the study, 510 overweight or obese adults from Murcia, south east Spain, who had enrolled in weight-loss clinics, were recruited, but as people on a special diet, under treatment with weight-loss medication, or who had a diagnosis of diabetes, chronic kidney failure, liver diseases, or cancer were excluded from the study, only 420 took part in a 20-week weight loss programme. Before starting the programme, which was based on following a Mediterranean diet, the group was subjected to a range of tests and questionnaires that gathered key information on body fat, blood tests relating to obesity, blood pressure, energy intake before and during treatment, energy expenditure, sleep duration and appetite hormone levels.
The results were that the participants who ate lunch before 3pm lost an average of 2.2kg more weight than those eating lunch after 3pm. Lunch is often eaten in the mid to late afternoon in Spain, and it is the main meal of the day. However, though we say breakfast is the most important meal of the day, the team of researchers found no link between the timing of breakfast or dinner and weight loss or better wellness. The amount of energy that was consumed and expended by the participants was similar, regardless of when they ate, so you could not explain the weight loss differences this way. The same can be said of sleep duration and appetite hormones, as these levels were also similar in both groups.
However, as both groups were on a weight-loss programme, it does not simply boil down to eating whatever you like before 3pm. The study also did not prove that eating lunch earlier makes you slimmer, or that you’ll put on weight if you take a late lunch. All it showed was that there was some sort of an association between the timing of lunch and weight loss. As to the reason why, there was none given and therefore the subject is in need of further research.