Eat More Calories in the Morning to Lose Weight

“Eat More Calories in the
Morning to Lose Weight” Mice are nocturnal creatures. They eat during the night
and sleep during the day. If, however, you just feed mice
during the day, they gain more weight than if you feed them a similar
amount of calories at night. Same food, about the same amount of
food, but different weight outcomes, suggesting that eating at
the “wrong” time may lead to disproportionate weight gain. In humans, that would
presumably mean eating at night. Weight management recommendations
often include advice to limit nighttime food consumption,
but this was largely anecdotal until it was first studied
experimentally in 2013. Researchers instructed a group of young
men to not eat after 7 p.m. for two weeks. Compared to a control period where
they continued their regular habits, after the night-eating restriction
they ended up about two pounds lighter.

This is not surprising, given
that dietary records show they inadvertently ate fewer
calories during that time. To see if the timing has metabolic effects beyond just foreclosing
eating opportunities, you’d have to force people to eat
the same amount of the same food, just at different times of the day. The U.S. Army stepped forward to
carry out just such an investigation. In the first set of experiments,
army researchers had people eat a single meal a day either
as breakfast or as dinner. The results clearly showed that the
breakfast group lost more weight. Check it out: Have people eat
only once a day at dinner, and their weight doesn’t change much. Have them eat once a day at breakfast,
and they lose about two pounds a week.

Like in the night-eating restriction
study, this is to be expected, given that people tend to
be hungrier in the evening. Think about it. If you went nine hours
without eating during the day you’d be famished, but people
go nine hours overnight all the time and don’t wake up ravenous. There is a natural circadian
rhythm to hunger that peaks at about 8 p.m. and drops down to
its lowest level at about 8 a.m. That may be why breakfast typically
is the smallest meal of the day. The circadian rhythm of our appetite
isn’t just behavioral, it’s biological. It’s not just that we’re
hungrier in the evening because we’ve been
running around all day. If you stayed up all night
and slept throughout the day, you’d still be hungriest
when you woke up that evening. To untangle the factors,
scientists use what’s called “forced desynchrony” protocol where
they lock people up in a room without windows in
constant unchanging dim light and make people sleep in staggered 20-hour cycles to
scramble them up.

That goes on for over a week,
so the study subjects end up eating and sleeping at different times
throughout all phases of the day. Then you can see if cyclical phenomena
are truly based on internal clocks or just a consequence of what you
happen to be doing at the time. For instance, there’s a daily
swing in our core temperature (blood pressure, hormone
production, digestion, immune activity, and
almost everything else, but let’s use temperature as an example). Your body temperature bottoms
out usually around 4 am, dropping from 98.6 °F
down to more like 97.6 °F. Now, is this just because your body
cools down as you’re sleeping? No, you can show experimentally
by keeping people awake and busy for 24 hours straight that it happens
at about the same time no matter what; it’s part of our circadian
rhythm, just like our appetite. It makes sense, then, if you’re
only eating one meal per day and you want to lose weight
you’d want to eat in the morning when your hunger hormones
are at their lowest level. OK, but then things start to get weird. The army scientists
repeated the experiment, but this time they had the
participants eat exactly 2000 calories, either as breakfast or as dinner.

That takes appetite out of the picture. They were also not allowed to exercise. Same number of calories, so
the same change in weight, right? No, the breakfast-only group still
lost about two pounds a week compared to the dinner-only group. Two pounds of weight loss eating
the same number of calories. That’s why this concept of chronobiology, meal timing—when to eat—
is so important…