You’ve long heard that eating your biggest meal in the morning and your smallest meal at night is the best way to stay slim and trim. But what’s the truth? What does science say about optimal eating times for keeping the weight off and staving off cardiovascular disease, diabetes and a host of other chronic illnesses?
Experts contend that while the quality of the food you eat is most important, the timing is a close second. Research shows that when people ate the same amount of calories each day but ate most of them in the morning and at lunch, they lost more weight than people who ate most of their calories in the evening, says Courtney Peterson, an associate professor of nutrition at the University of Alabama at Birmingham.
She says that they were also less hungry throughout the day. “It’s a one-two punch because those who ate the most calories at night lost less weight but were also more hungry,” says Peterson.
What’s Happening in the Body?
According to experts, it’s all about how your body reacts to hunger. “Subjective hunger,” or how hungry you claim to be, is higher later in the day as are levels of the hunger hormone ghrelin, says Peterson. This is the hormone that signals to your brain that you’re hungry and it’s time to eat.
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You also burn fewer calories when you eat later in the day because of what’s called the “thermic effect.” This is the number of calories required for your body to digest, absorb and metabolize food. “Genes that are involved in burning and storing fat seem to perform worse later in the day and tend to activate pathways in the brain that store fat more easily,” says Peterson.
But it’s not just that weight loss is dependent on the time of day that you eat. Eating earlier in the day may also be beneficial for overall health, for example, keeping blood sugar in check as well as lowering blood pressure and improving thyroid health. A July 2021 study published in the journal Nutrients found that eating an earlier dinner improved blood glucose levels. Additionally, a November 2021 study published in the journal Epidemiology and Health found that eating later in the day increased cardiovascular risk factors like blood triglyceride concentration.
All of these mechanisms depend on the time of day because of the body’s circadian system or internal biological clock. The circadian system is also the reason why your best sports performance is in the afternoon, and you’re better at falling asleep at night.
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"Your body is optimized to perform certain tasks at certain times of the day, which makes sense from an evolutionary perspective,” says Peterson. Millions of years ago, the sun produced most of the light which early humans depended on to live, and therefore, we were much less active at night.
When Should You Be Eating?
Dietitian and author Carolyn Williams says that it’s also important to note that our body needs to have set times when we eat and when we don’t eat. The body is set up hormonally and metabolically to require at least a 12-hour window when we aren’t taking in food, says Williams.
That’s how we lived up until the 1970s when snack foods and the 24-hour availability of food became a mainstay. The body is better able to shed pounds when there’s at least a 12-16 hour window when we’re not eating. “Prior to a half-century ago, most foods were eaten at home, there wasn’t nearly as much snacking and the kitchen was closed for the night after dinner time,” says Williams.
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If you tend to eat dinner later at night, it’s still important to fast for 12-16 hours. That means if you eat your dinner at 9 p.m., then you shouldn’t eat again until between 9 a.m. and 1 p.m. the next day.
Just because you eat dinner late at night, it doesn’t mean you’re doomed. But, it is worth making your last meal of the day the smallest of the three. And most importantly, after dinner each evening, the kitchen should be closed for business until it’s time for breakfast the next morning.
