"I only eat one meal a day. How can I possibly be gaining weight?"
While it seems like eating only one meal a day would result in negative calorie balance (expending more calories than consuming) and weight loss, recent research shows the opposite.1 Leading weight loss researchers analyzed data on eating frequency (self-reported meals and snacks consumed per day) and physical activity in weight loss maintainers who had reduced from overweight/obese to normal weight, normal weight individuals, and overweight individuals. Results showed:
The results of this study are consistent with another published report of eating frequency in successful weight loss maintainers in which participants in the National Weight Control Registry reported consuming approximately 5 eating occasions per day. Likewise, the American Dietetic Association's Evidence Analysis Library gives the following a "Fair" recommendation for adult weight management (meaning practitioners should generally follow it but remain alert to new information and be sensitive to patient preferences):
Total caloric intake should be distributed throughout the day, with the consumption of 4 to 5 meals/snacks per day including breakfast. Consumption of greater energy intake during the day may be preferable to evening consumption.
The science behind eating 4 to 5 meals/snacks per day for weight management is not clear. For some people it may help prevent extreme hunger and overeating at mealtimes. In the study described above authors posed a possible relationship between eating frequency and physical activity. More meals more physical activity?
As with many dietary recommendations, however, it is important to consider the individual. People who have difficulties selecting healthy snacks or to stop thinking about and/or eating foods might do better on three structured meals a day. Thus, when recommending 3 meals and 2 snacks per day, be clear that snacks should be planned (i.e., type of food and time to be eaten) and healthy (e.g., fruits, vegetables, small handful of nuts).
1Bachman, J. L., Phelan, S., Wing, R., & Raynor, H. A. (2011). Eating frequency is higher in weight loss maintainers and normal-weight individuals than in overweight individuals. J Am Diet Assoc., 111(11), 1730-1734. doi: 10.1016/j.jada.2011.08.006