When I started bodybuilding some 7 years ago, everyone I knew ate big breakfasts and 6 meals a day. It was also commonly accepted that carbs should be limited to the start of the day while ‘slow’ forms of energy should be consumed later in the day. Before bed, people said to take casein with some fat to prevent night time catabolism. I can’t even begin to recount how often I’ve eaten oatmeal with whey for breakfast and cottage cheese with flax seed before bed.
These days, things are a lot different. Pretty much all of the forms of nutrient timing I just listed are known to be ineffective. You can skip breakfast without sacrificing gains to cortisol, absolute meal frequency is irrelevant, carbs and fats can be eaten at any time of day and you can go without food for a long time without losing muscle.
These changes have caused many people to be skeptical of nutrient timing as a principle. This skepticism is most strongly represented by the nihilist approach to dieting called IIFYM: if it fits your macros. IIFYM in its purest form (!) states that all that matters in a diet is its macronutrient composition. The amounts of carbs, fat and protein and the resulting total energy intake are all that matters according to pure IIFYM. When you eat those macros is irrelevant: nutrient timing doesn’t enter into it and can go the way of the dodo. While simplistic, this skeptical approach to nutrition is much more scientific than the prevailing broscience attitude of “let’s try everything that sounds cool even if it’s just a theory without any empirical support”.
In the absence of evidence, there is no reason to believe a statement. However, there actually is evidence that IIFYM may be missing something. This something, or something of this something, is circadian rhythm protein timing (CRPT). Let’s look at the evidence.