Chrono-nutrition is a relatively new area of nutrition science exploring the ways our circadian clock influences our metabolic functions. To put it simply, there is increasing evidence to suggest when we eat can be just as important as what we eat.
For decades there have been questions over whether it is optimal to eat the biggest meal of the day in the evening. While some research has linked obesity with eating the majority of one’s daily caloric load late in the day, it is clear each person’s biological clock can be different. So any general one-size-fits-all eating rule may be futile.
This new research set out to specifically look at how the time of day influences the metabolism of proteins, particularly in regards to skeletal muscle growth. The first step focused on mice fed two meals of varying protein content a day.
The researchers found protein intake in the morning more readily induced skeletal muscle growth than protein consumed at night. Even more interestingly, the rate of muscle growth was 17 percent higher in the mice fed an 8.5 percent protein breakfast compared to mice fed an 11.5 percent protein dinner.
A further experiment with mice lacking the genes that regulate circadian rhythms found no difference in skeletal muscle growth between breakfast and dinner. This affirmed the influence an organism’s biological clock seems to have on protein metabolism.
The final part of the research recruited 60 subjects selected from a diet survey. Half the cohort habitually consumed the majority of their daily protein intake at dinner, while the other half ingested more protein at breakfast.
Those subjects eating a high volume of protein for breakfast displayed higher skeletal muscle mass and performed better on a grip strength test. The researchers are cautious to note this human part of the study is not definitive evidence of a causal connection between time of protein intake and skeletal muscle mass. Instead it simply indicates a correlation that could relate to the animal study findings.
Shigenobu Shibata, lead on the research from Waseda University, says Western and Asian diets tend to have low-protein volumes in breakfast meals. He says while more research is certainly needed to better understand exactly how the circadian clock influences protein metabolism and muscle volume, the evidence so far suggests less protein should be consumed in evening meals and more in morning meals.
“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,” says Shibata. “Our findings strongly support changing this norm and consuming more protein at breakfast or morning snacking time.”
The new study was published in the journal Cell Reports.
More protein at breakfast makes for better muscle growth, study indicates [New Atlas]