We have known for more than half a century that our glucose tolerance decreases with the passing of the day; That is, the body’s ability to maintain blood sugar levels at a normal level decreases.

If you use an intravenous (IV) solution to drip glucose into your vein at a regular rate throughout the day, you’ll find that by 8 p.m. your blood sugar begins to rise, even though you haven’t eaten and the rate at which glucose pumps into your blood hasn’t changed.

It’s the same amount of sugar being pumped into your body every minute, but its ability to handle it deteriorates in the evening and returns to normal again in the morning.

Eating a meal at eight in the evening may double the blood sugar level, unlike eating the same meal at eight in the morning. That is, you ate twice the amount of food. Your body does not expect you to eat after nightfall. The human race only discovered how to use fire about a quarter of a million years ago , so our bodies are not used to always having restaurants open and eating all the time.

One test for diabetes, called a glucose tolerance test , tests how quickly the body gets rid of excess sugar in the blood. You take a glass of water dissolved in about four and a half tablespoons of regular corn syrup, and then your blood sugar is measured after two hours. At that point, your blood sugar should be less than 140 milligrams per deciliter.

If it is between 140 and 199, it is considered prediabetes, and if it is 200 or more, it is a sign of diabetes.

The circadian rhythm of changes in glucose tolerance is so powerful that a person’s test result may be normal in the morning and change to indicate prediabetes in the evening. And people with prediabetes with an average blood sugar of 163 at 7 a.m., end up testing out as a full-blown diabetic by 7 p.m., with a blood sugar level of over 200.

Choosing low-sugar foods may help you lose weight, but the timing of eating them is important.

Because the circadian pattern of glucose tolerance is affected by the timing of eating, eating a low-sugar food at night can lead to a greater rise in blood sugar than eating a high-glycemic food in the morning.

This happens because our metabolism slows down during the night, and researchers have found that eating a bowl of whole grains at 8 p.m. leads to a blood sugar spike that’s just as dramatic as eating a sweetened breakfast cereal at 8 a.m. Eating high-sugar foods in the evening is the worst thing to do.

So, if you plan on eating processed cereals that are full of sugar, they may be less harmful if you eat them in the morning. Thus, it is possible that decreased glucose tolerance throughout the day can help us understand and explain the positive results in terms of weight loss due to consuming the most calories at the beginning of the day.

The difference is also evident even in the comparison between eating lunch early and eating it late. Some people were randomly assigned to eat a large lunch at 4:30, and the result was a 46% increase in their blood sugar, compared to eating the same meal several hours earlier at 1 p.m.

Eating the same food at 7 a.m. can lower blood sugar by 37% than eating the same food at 1 p.m.

There doesn’t seem to be any difference between eating a meal at 8 pm and eating the same meal at midnight, both times being too late.

But eating that late, whether it’s 12 a.m. or even 11 p.m., can seriously disrupt your body’s circadian rhythm, and can disrupt your metabolism the next morning, leading to a spike in blood sugar after breakfast, compared to eating the same dinner at 6 pm the previous day.

Therefore, these discoveries in chronobiology bring the debate over the importance of breakfast back to its starting point.

Skipping breakfast not only impedes weight loss in general, but also impairs the body’s ability to control daily blood sugar in diabetics and non-diabetics.

See how people who skip breakfast have high blood sugar even in their sleep and 20 hours later?

This may help explain why people who skip breakfast are more likely to develop type 2 diabetes in the first place. They also have increased rates of heart disease and atherosclerosis in general.

Is this just because skipping breakfast often combines with other unhealthy choices like smoking and poor eating habits in general?

The association between skipping breakfast , heart disease, and early death in general appears unrelated, based on attempts to monitor for these confounding factors.

But we couldn’t verify that until after it was put to the test. Does skipping breakfast lead to high cholesterol, for example?

Yes, the result was a significant increase in LDL (bad cholesterol) in those randomized to a trial of skipping breakfast by 10 points in just two weeks.

An Israeli study found that the percentage of triglycerides in the group breakfast of kings, lunch of princes and dinner of the poor improved significantly and decreased by 60 points, while its percentage worsened in the group that ate meals in the reverse order, and increased by 26 points.

Thus, eating more calories in the morning than in the evening may have a triple benefit: greater weight loss, better blood sugar control, and a lower risk of heart disease.

So if you’re going to miss a meal, whether due to intermittent fasting or restricting eating times by keeping all of your meals in a fixed amount of time each day, it may be safer and more effective to skip dinner than to skip breakfast.