It's not called "the most important meal of the day" for nothing…

Karla Walsh; Reviewed by Jessica Ball, M.S., RD
July 21, 2021
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We like to think of protein as an irreplaceable body building block. It's the "glue" that holds our cells together in everything from our hair to our nails to our muscles, and it also aids in the formation of many important antibodies and hormones. Not to mention, protein helps us feel full and satisfied after we fuel up with it.

How much each person needs is very individual (learn how to calculate exactly how much protein you should aim for each day here), and while it is crucial for our existence, it is certainly possible to overdo it. Science says that we can only absorb up to 25 grams at one sitting—which is equal to 3 ounces of chicken breast, 1 cup of cottage cheese or 4 eggs—and anything over 140 grams of protein per day or so is probably unnecessary. (Wildly high-protein diets can throw your body out of whack in these 8 ways, plus it might crowd out other important macronutrients like heart-healthy fats and fiber-rich carbs.)

Female basketball player flexing on basketball court
Credit: Getty Images / miodrag ignjatovic

So now that we know a rough idea about how much protein to eat, what about when? This is what researchers from Waseda University in Japan set out to discover in their new study, published July 6 in the journal Cell Reports. After studying mice and humans, they found that front-loading the day with enough protein at breakfast leads to a larger increase in muscle size and function than consuming more protein at dinner.

To begin, they fed laboratory mice 2 meals per day containing either:

  • Higher protein, or 11.5% of total calories, or
  • Lower protein, or 8.5% of total calories

The mice that ate the higher protein meal early in the day at "breakfast" displayed more muscle growth than their peers who were fed the higher protein meal later in the day for "dinner."

To confirm this association in humans, the research team led by Shigenobu Shibata, a professor for the school of advanced science and engineering at Waseda University, recruited 60 women aged 65 or above to participate. Those who had more protein at breakfast than dinner showed better muscle function, determined by their skeletal muscle index (SMI) and grip strength.

According to professor Shibata, a "protein-rich diet at an early phase of the daily active period, that is at breakfast, is important to maintain skeletal muscle health and enhance muscle volume and grip strength."

While more research is needed to test this concept in larger and more diverse populations, and at different macronutrient ratios, it certainly can't hurt to subtly shift more of your overall daily protein intake to the a.m.—keeping it around that 25 grams of protein per meal or snack, of course. Give this a go by trading a bowl of cold cereal and a piece of fruit for a cup of Greek yogurt topped with nuts and fresh berries, or try a couple of our Greek Muffin-Tin Omelets with Feta and Peppers with a banana instead of opting for a regular bakery muffin.

"For humans, in general, the protein intake at breakfast averages about 15 grams, which is less than what we consume at dinner, which is roughly 28 grams. Our findings strongly support changing this norm and consuming more protein at breakfast or morning snacking time," Professor Shibata says in a brief about the study.

Craving some inspiration? Try our 7-day meal plan of satisfying high-protein breakfasts to kick things off, then sample your way through any or all of these 16 make-ahead high-protein breakfasts.