There is an old adage: “eat like a king for breakfast, a prince for lunch, and a pauper for dinner.” With the rise of the intermittent fasting culture and time-restricted eating windows, the way we eat is also being shaped by the time we eat. A study published on July 24 confirmed what we’ve intuitively known about mealtimes and amounts: eat most of your calories earlier in the day to maximize health.
Earlier in the day, some of the body’s metabolic functions (such as insulin sensitivity and peak thermic effects of food) are working with natural circadian rhythms. These rhythms peak between the morning and noon. By restricting eating to within an 8-11-hour window, researchers have found that even though it won’t give you more energy, it will increase fat burning and also reduce appetite.
Eating late at night—when you are out of sync with your body’s natural circadian rhythms—has been proven to increase weight gain and promote metabolic dysfunction in both humans and rodents. This study focused on two groups that were given the same number of calories but distributed differently throughout the course of the day. One group ate on a 12-hour eating period between 8:00 AM and 8:00 PM, while the other ate between 8:00 AM and 2:00 PM.
The group with the 12-hour eating window was served meals at 8:00 AM, 2:00 PM, and 8:00 PM. The more restricted group ate meals at 8:00 AM, 11:00 AM, and 2:00 PM. The researchers determined that the group with the restricted 6-hour window (from 8:00 AM to 2:00 PM) worked for weight loss, but in a surprising way; it reduced appetite more than anything else.
Ghrelin, the hormone responsible for feelings of hunger, was decreased, and participants felt an increase in fullness. Eating like the adage says and having larger breakfasts reduced the ghrelin throughout the day. The study did note that the restricted 6-hour group also had an increase in fat burning, but they believe the biggest mechanism behind the results was the effect on appetite. The researchers pointed out a paradox about restricting eating to a daytime-period only: it actually reduced hunger fluctuations and kept hunger levels more stable during the day, even well into the evening when food intake was restricted.
- Ravussin, Eric, et al. “Early Time‐Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans.” Obesity, 24 July 2019, doi:https://doi.org/10.1002/oby.22518.