Protein at breakfast builds more muscle than protein at dinner

Chrononutrition is a field that ties maximum nutritional benefit from food to the time of day a person consumes it.
A new study, led by scientists from Waseda University in Tokyo, Japan, concludes that protein consumed in the morning promotes muscle growth more than protein eaten later in the day.
The authors conducted their research in both mice and humans.

Most people have heard the expression, “you are what you eat.” A new study from researchers at Waseda University in Tokyo, Japan, suggests that it is also true that “you are when you eat,” at least when it comes to protein.

According to the study, consuming protein early in the day leads to greater muscle growth.

The study’s lead author Prof. Shigenobu Shibata says:

“For humans, in general, the protein intake at breakfast averages about 15 grams (g), which is less than what we consume at dinner, which is roughly 28 g. Our findings strongly support changing this norm and consuming more protein at breakfast or morning snack time.”

The study appears in the journal Cell Reports.

Life and the circadian rhythm

The human body typically follows the same natural 24-hour pattern each day. This is the body’s circadian rhythm. The circadian rhythm influences the behavior of cells and body chemistry, affecting processes such as metabolism, digestion, and growth.

Certified nutritionist and acupuncturist Dr. Jerry Bailey, who was not involved in the study, explained to Medical News Today why it is important to respect the body’s circadian rhythm:

“Keeping our natural light [and] dark circadian cycle in tune is essential to both short-term and long-term health. We see in shift workers, in particular night shift, that their health, hormone, and circadian cycles are completely disrupted, which induces a state of neurological, hormonal, and immunological depletion.”

Chrononutrition is a research field that explores the possible benefits of aligning the consumption of foods with the circadian rhythm.

Protein in the morning

While previous research suggests that eating protein at breakfast and lunch may promote more robust muscle growth, this study investigates this phenomenon more thoroughly and zeroes in on breakfast time.

Dr. Bailey said that this makes sense because “We are essentially primed for growth, strength, hypertrophy in the morning.” This is the time of day, says Dr. Bailey, that is “the most metabolically active or in a potentially anabolic (growth) state.”

A three-pronged investigation

The authors of the study investigated the effect of consuming protein early in the day from three angles.

The researchers fed two groups of laboratory mice protein in the form of branched-chain amino acid (BCAA) supplements either at breakfast or at dinner. At breakfast, the protein constituted just 8.5% of the meal they consumed, while at dinner, they consumed a higher percentage of protein at 11.5%.

Despite consuming less protein, muscle growth was greater in the mice who had protein at breakfast.

To ascertain muscle growth, researchers measured “muscle hypertrophy” — an increase in the size of muscle cells — in the plantaris muscle on the back of the lower leg of the mouse.

To confirm that the difference between the two groups of mice was the time of day at which they consumed their protein, the researchers repeated the experiment with muscle-specific Bmal1 knockout mice. These mice lack the Bmal1 gene in their muscle cells, which is essential for maintaining a circadian rhythm.

The scientists found no difference in the effect of breakfast or dinner protein on muscle hypertrophy in these mice.

Finally, to see if the effect would carry over to humans, the researchers recruited 60 older women whose daily intake of protein was in line with the recommendations of Japanese health experts. Half the women reported eating more protein at breakfast than dinner, and the other half did the opposite.

While there was no difference between the two groups in terms of activity level, body mass, height, BMI, fat mass, physical function, or dietary intake, the group that ate their protein early in the day had higher muscle mass.

For the women who got their protein early in the day, skeletal muscle mass index and grip strength were significantly higher.

Eating smarter

Medical News Today spoke with Cleveland Clinic dietitian Kristin Kirkpatrick, who was not involved in the research. She pointed out that the study proposes “eating higher amounts of protein at breakfast instead of the traditional higher amount at dinner” to reap the benefits.

Dr. Bailey said of dinnertime protein, “Protein, when not used for muscle growth, would typically then be broken down to be stored as fat components in the body.”

MNT asked Kirkpatrick for some morning-protein ideas beyond traditional breakfast fare. “I love adding in protein powders to boost intake of protein,” including adding it to steel-cut oats. She also recommends protein bars, as well as “nut butter, which will have […] both healthy fat and protein on top of sprouted grain toast or nut-based crackers.”

The takeaway from the study is that to help ensure we remain healthy and strong — even for older adults, as shown by the study — it might be a good idea to move our protein intake to our early waking hours.

Written by Robby Berman on July 26, 2021 — Fact checked by Ferdinand Lali, Ph.D.

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