Eating rather than skipping breakfast results in lower blood sugars the whole day

Posted on by Jesse Santiano, M.D.

This article presents four studies conducted among healthy people, those with metabolic syndrome and those with type 2 diabetes showing that eating breakfast results in better blood sugar levels for the whole day.

Background

Before dawn, the body prepares for morning activities by secreting counter-regulatory hormones, including growth hormone, glucagon, cortisol, and adrenaline.

They are called counter-regulatory because they counter the effects of insulin. They work to increase blood sugar and blood pressure.

Blood sugar fuels the skeletal muscles. And the rise in blood pressure ensures adequate blood goes to the brain upon standing. During the night, the kidneys continue to make urine from the blood, and blood volume decreases a bit in the process.

If the blood pressure does not go up in the morning, lightheadedness or dizziness can occur, and at worse, a person may pass out as we get out of bed.

The human body’s circadian rhythm dictates this rise in counter-regulatory hormones. It is another reason we do not die from hypoglycemia or low blood sugar at night when we sleep and do not eat. (The situation is different if someone is taking diabetes medications.)

Once breakfast is eaten, which typically contains carbohydrates, proteins, and fats, insulin rises to store the ingested glucose, amino, and fatty acids.

The counter-regulatory hormones decrease after a meal, and that’s because their blood sugar-raising function is not needed anymore.

So what happens to the adrenaline and cortisol levels if people don’t eat breakfast?

Answer: the effects of adrenaline and cortisol persist, resulting in higher blood sugar all day. That conclusion is based on three studies presented.

Healthy men who skipped breakfast have higher blood sugars

Ogata et al. studied ten young, healthy men aged 22-29 who participated in two trials, with and without breakfast.[1]

They found that their after-meal or post-prandial blood sugar was higher when they skipped breakfast. High after-meal blood sugar levels (>140mg/dl or 7.8mmol/L) can lead to atherosclerosis formation.

As most know, atherosclerosis can eventually lead to a heart attack or stroke. The two leading causes of death. You can read the study about it at — After-meal high blood sugar predicts Atherosclerosis better than Fasting blood sugar and HbA1c

Additionally, Ogata et al. found that the blood sugar of those who skipped breakfast was higher at 11:00 pm. Not only that but on the sixth day, their level of physical activity also decreased, and their average blood sugar was higher than those who ate three meals a day. [1]

They found that when the subjects missed their breakfast, they tended to eat more during lunch and dinner to compensate for the lost calories.

Higher blood sugar in those with Metabolic Syndrome who skipped breakfast

Anyone who has three of the following has metabolic syndrome. [2]

  1. A waist circumference of more than 40 inches in men and 35 inches in women
  2. Elevated triglycerides 150 milligrams per deciliter of blood (mg/dL) or greater
  3. Reduced high-density lipoprotein cholesterol (HDL) less than 40 mg/dL in men or less than 50 mg/dL in women
  4. Elevated fasting glucose of l00 mg/dL or greater
  5. Blood pressure values of systolic 130 mmHg or higher and/or diastolic 85 mmHg or higher

40% of people aged 40-59 and almost 50% of both sexes aged  ≥ 60 in the US had metabolic syndrome in 2016. Those percentages are probably much higher now after the COVID lockdowns.

Source: Trends in the Prevalence of Metabolic Syndrome in the United States, 2011-2016. JAMA. 2020;323(24):2526–2528

In metabolic syndrome, high blood sugar, inflammatory cytokines from obesity, hypertension, high triglycerides, and low HDL work together to form several common disease conditions. You can read about them in Diseases Associated with Metabolic Syndrome.

Nas et al. conducted an interesting study on 17 participants with metabolic syndrome.[4]

Using a randomized controlled cross-over trial, all 17 subjects did all the tests and control diets on different days. All diets have the same number of calories in 24 hours. (55% carbohydrate, 30% fat, and 15% protein)

The test diets are three breakfast-skipping days (BSD) and three dinner-skipping days (DSD) separated by a conventional 3-meal day (control)

The results are a mixture of good and bad. On breakfast-skipping and dinner-skipping days, the 24-h energy expenditure was higher. (BSD: +41 kcal/day; DSD: +91 kcal/d; both P < 0.01). That means more weight loss.[4]

Additionally, when they skipped breakfast, they lost more fat. (+16 grams/day; P < 0.001)

Here is the not-so-good part. Insulin resistance and blood sugar were higher when they did not eat breakfast.

The postprandial homeostasis model assessment index (+54%) and glucose concentrations after lunch (+46%) were, however, higher on the BSD than on the DSD (both P < 0.05).

The Homeostatic Model Assessment Index is a measure of insulin resistance.

Insulin resistance means the skeletal muscles and the liver cells do not accept blood glucose with the typical insulin levels. This is what happens in those with prediabetes and type two diabetes.

Insulin resistance is expected in teens but is terrible after that age. As a result of the body not responding to normal insulin levels, the pancreas has to produce more insulin to lower the blood sugar, creating hyperinsulinemia or high insulin levels in the blood.

Hyperinsulinemia can affect the skin and internal organs and produce other disease processes. I presented them in my article, Hyperinsulinemia. 

You are not wrong if you are starting to understand that many other disease conditions follow a persistently high blood sugar.

More pro-inflammatory white blood cells

Another finding of Nas et al. is that the white blood cells (WBCs) tend to be more pro-inflammatory when the participants skip breakfast.[4]

We need WBCs to protect against infections when they use their pro-inflammatory cytokines. However, without infection, the cytokines will act on the human body’s cells.

Previous studies have shown that high blood sugar enters the white blood cells, giving them more fuel to make pro-inflammatory cytokines. Examples are interleukin-6 and tumor necrosis factor-alpha.

These cytokines affect the blood vessels and other organs like the heart, brain, and kidney to cause inflammation and cause conditions like atherosclerosis, hypertension, and diabetes.

Related: Inflammation: Dolor, Tumor, Rubor, and Calor

To summarize to findings of Nas et al., those who skipped breakfast tended to have higher post-prandial blood sugars, low-grade inflammation, and higher blood sugar all day in healthy male subjects.[4]

Skipped Breakfast and metabolic syndrome development

A larger study used data from the 2016-2020 Korea National Health and Nutrition Examination Survey and included 22,699 individuals.[5]

The survey showed that women who ate two meals per day and skipped breakfast had increased odds of elevated fasting blood glucose levels and triglycerides.[5]

In contrast, women who skipped dinner had reduced odds of having elevated fasting blood glucose levels. [5]

Among Korean men, those who skipped breakfast had increased odds of developing metabolic syndrome, abdominal obesity, and higher triglycerides than those who consumed three meals daily.[5]

Interestingly, if men skipped lunch but ate breakfast and dinner, they had higher odds of elevated fasting blood glucose levels than those who consumed three meals daily.[5]

In summary, the extensive Korean survey showed that men and women who don’t eat breakfast but eat lunch and dinner tend to have a greater tendency to develop metabolic syndrome.

People with Type 2 diabetes who skipped breakfast tend to have higher after-meal blood sugar.

A study from Israel was conducted on 22 patients with diabetes. Ages were 56.9 ± 1.0 years, BMI 28.2 ± 0.6 kg/m2 (overweight), and HbA1c of 7.7 ± 0.1% (61 ± 0.8 mmol/mol). [6]

The study is a cross-over design. All participants went through two test days: one with breakfast, lunch, and dinner (YesB) and another with lunch and dinner but no breakfast (NoB). [6]

RESULTS

When the subjects had no breakfast, they had the following blood results after lunch. Comparison is made to when they had breakfast. [6]

  1. Higher blood sugar by 36.8% compared to when they had breakfast.
  2. Higher free fatty acids by 41.1%. Fatty acids come from dietary fat and oil ingestion.
  3. Higher glucagon by 14.8%. Glucagon is a hormone that increases blood sugar.
  4. Insulin, the hormone that decreases blood sugar and fatty acids, was lower by 17%
  5. GLP-1, or glucagon-like peptide 1, the hormone that promotes insulin secretion, is lower by 19%.

After dinner, the following are the blood results when the participants had no breakfast. Comparison is also made to when they had breakfast.[6]

  1. Glucose 26.6% higher
  2. Free fatty acids are 29.6% higher
  3. Glucagon 11.5% higher
  4. Insulin was 7.9% lower
  5. GLP-1 was 16.5% lower

The high glucose and fatty acids are the effect of the lower levels of insulin and GLP-1 and higher glucagon.

Significantly, insulin peak was delayed 30 minutes after lunch and dinner on no-breakfast days compared to breakfast days. This means a longer time of high blood sugar levels.

In summary, in subjects with type 2 diabetes, missing breakfast results in higher after-meal or post-prandial blood sugars after both lunch and dinner.[6]

The graph below shows a higher blood glucose/sugar level after lunch and dinner when breakfast is skipped than when breakfast is eaten. Arrows denote the meals.

Source: Fasting until noon triggers increased post-prandial hyperglycemia and impaired insulin response after lunch and dinner in individuals with type 2 diabetes: a randomized clinical trial. Diabetes Care. 2015 Oct;38(10):1820-6.

As mentioned earlier, high levels of after-meal blood sugars can lead to atherosclerosis formation that can eventually cause heart attacks and strokes.

Conclusion

The studies presented here consistently show that eating breakfast results in better blood sugar control throughout the day and, more importantly, can prevent after-meal blood sugar spikes that make you at risk for cardiovascular disease.

The result applies to healthy people with metabolic syndrome and type 2 diabetes.

High blood sugars can also make the white blood cells produce more pro-inflammatory cytokines that can cause chronic inflammatory conditions like diabetes, hypertension, and atherosclerosis.

Someone considering intermittent fasting may choose to have an earlier or lighter dinner to obtain its benefits.

Adelle Davis, born February 25, 1904, is an American writer and nutritionist. She is “the most famous nutritionist in the early to mid-20th century.” She advocated for improved health through better nutrition. She is known for the quote,

Eat breakfast like a king, lunch like a prince, and dinner like a pauper.

Don’t Get Sick!

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Everyone should use their two-hour after-meal blood sugar. Glucometers are available over the counter, and I use the Care Touch glucometer from Amazon.

Related: 

  1. How often do you do the post-prandial sugar test?
  2. Blood Glucose Spike and its Prevention
  3. Testing Post Prandial Glucose Level after a Feast
  4. After-meal blood sugar spikes as a cause of vascular failure
  5. Veggies Meat Carbohydrate Sequence Prevents After Meal Sugar Spike
  6. A Healthy Lifestyle is as effective as Voglibose and Nateglinide in Lowering 10-year Cardiac Mortality
  7. Intermittent fasting Reverses Endothelial Dysfunction
  8. Walk After Meals to Prevent Sky High Blood Sugars

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References:

  1. Ogata H, Kayaba M, Tanaka Y, Yajima K, Iwayama K, Ando A, Park I, Kiyono K, Omi N, Satoh M, Tokuyama K. Effect of skipping breakfast for 6 days on energy metabolism and diurnal rhythm of blood glucose in young, healthy Japanese males. Am J Clin Nutr. 2019 Jul 1;110(1):41-52. doi: 10.1093/ajcn/nqy346. PMID: 31095288.
  2. Swarup S, Goyal A, Grigorova Y, et al. Metabolic Syndrome [Updated 2022 Oct 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459248/
  3. Hirode G, Wong RJ. Trends in the Prevalence of Metabolic Syndrome in the United States, 2011-2016. JAMA. 2020;323(24):2526–2528. doi:10.1001/jama.2020.4501
  4. Nas A, Mirza N, Hägele F, Kahlhöfer J, Keller J, Rising R, Kufer TA, Bosy-Westphal A. Impact of breakfast skipping compared with dinner skipping on regulation of energy balance and metabolic risk. Am J Clin Nutr. 2017 Jun;105(6):1351-1361. doi: 10.3945/ajcn.116.151332. Epub 2017 May 10. PMID: 28490511.
  5. Park H, Shin D, Lee KW. Association of main meal frequency and skipping with metabolic syndrome in Korean adults: a cross-sectional study. Nutr J. 2023 May 11;22(1):24. doi: 10.1186/s12937-023-00852-x. PMID: 37165359; PMCID: PMC10173485.
  6. Jakubowicz D, Wainstein J, Ahren B, Landau Z, Bar-Dayan Y, Froy O. Fasting until noon triggers increased post-prandial hyperglycemia and impaired insulin response after lunch and dinner in individuals with type 2 diabetes: a randomized clinical trial. Diabetes Care. 2015 Oct;38(10):1820-6. doi: 10.2337/dc15-0761. Epub 2015 Jul 28. PMID: 26220945.

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