Читать книгу The Renaissance Diet 2.0 - Mike Israetel, James Hoffmann - Страница 74

Protein intake supports homeostasis as the body constantly breaks down and rebuilds its structural and functional proteins. The protein needed for this turnover can come from the diet or, if the diet is insufficient, muscle tissue. Generally, under hypercaloric conditions, sufficient protein intake supports muscle growth. Under isocaloric or hypocaloric conditions, sufficient intake helps prevent muscle loss.

Interestingly, the human body can only use so much protein at a time to build or maintain muscle. The literature shows roughly four evenly spaced meals, each containing one-fourth of your daily protein needs, supplies sufficient protein at a usable rate. A 200-lb. athlete who needs around 200 g of protein per day should therefore consume meals of no more than 50 g of protein at a time for maximum protein utilization. Any additional protein per meal will just be burned for energy. Although there are no direct drawbacks to eating extra protein per meal, if one is constrained by calories on a fat-loss diet, eating more than one-fourth of one’s daily protein per meal will mean protein will be insufficient in later meals. This is often misunderstood to mean that protein will not be digested or used at all after a certain per meal threshold; however, this upper limit pertains only to skeletal muscle protein synthesis. If you eat all your daily protein in one meal, the protein will still be digested and used for other various bodily functions, but only about one-fourth will go toward skeletal muscle growth or maintenance.

Figure 4.3 A theoretical graph illustrating the concept that meals themselves will cause some fat gain (dark areas), and spaces between meals will case some fat loss (light areas), resulting in no net fat gain if the diet is isocaloric.

There are mechanistic reasons to expect that uneven protein distribution across meals is suboptimal. Research has yet to confirm exact numbers, but approximately one-eighth of daily recommended protein intake per meal is a safe minimum to set for muscle maintenance. For a diet with 200 g of protein recommended per day, less than 25 g might not be enough protein per meal, and more than 50 g per meal will leave other meals without protein. Thus, eating between one-eighth and one-fourth of daily intake per meal is recommended (figure 4.4). There is some flexibility here: If you under-eat protein a bit at one meal and overeat at the other, some compensation occurs. This is a relatively narrow margin, though; when some meals are overly heavy with protein or smaller protein consumptions are followed by long stretches without eating, you run the risk of muscle loss.

It is particularly important to supply sufficient protein at timely intervals during hypocaloric diets when much of the ingested protein is burned for energy and only a fraction is used for muscle-specific functions. In fact, because of the general energy surplus on a hypercaloric diet, protein needs are lower (as low as 0.7 g per pound per day) than they are during a hypocaloric diet (up to 1.2 g per pound per day to prevent muscle loss). Meal timing choices are still relevant on a hypercaloric diet, as amino acids are in constant demand in order to supply FSR curves for muscle growth (figure 4.5).

Figure 4.4 Eight smaller meals (depicted by the smaller waves under the dotted line) provide a faster initial rise, as well as a more rapid drop in blood nutrients. Four larger meals (depicted by the larger waves above the dotted line) provide a slower rise and drop in blood nutrients. The dotted horizontal line depicts average nutrient amounts in the blood.

Figure 4.5 When the graphed line of protein intake is above the FSR threshold (dotted line), amino acids are available in the bloodstream for maximal muscle growth. Periods in which not enough amino acids are available are indicated by the shaded areas below the dotted line. A. Depicts smaller protein amounts eaten more frequently, supplying amino acids for maximal FSR for most of the time shown. B. Depicts a large amount of protein eaten at one time, followed by a long period without protein consumption. Because FSRs are limited, even though the total protein eaten in A and B is equivalent, option B (one large protein meal) facilitates less total muscle growth.

Though it is likely unnecessarily tedious, we can also examine per-hour protein needs. The actual process of muscle growth is measured by the FSR of muscle tissue. Right after weight training, these rates rise for up to 24 hours. Once the FSR peaks, it can take days to fall back to baseline. Therefore, the real “post-workout anabolic window” is between one to three days post training. Because most people are training multiple times a week, the demand for amino acids to supply FSR is rather stable as another workout is always pushing them back up before they can fall to baseline again (figure 4.6). This means that our bodies need a certain amount of protein hourly, no matter what time of the day we worked out, slept, or whatever else. We can also divide our daily protein dose by the 24 hours in a day to get our per hour protein needs, though this may be best suited for thought experiments and not practical dieting.

Figure 4.6 A. An incorrect representation of FSR curves following lifting sessions. B. An accurate representation of FSR curves following lifting sessions. FSR rises slowly for many hours and stays elevated for days.

For example, an athlete who weighs 240 lb. needs 10 g of protein per hour of the day (240 g/24 hr.). If our athlete wanted to eat two meals at three hours apart, they would need to eat about 30 g of protein at meal one to supply amino acid needs across those three hours between meals. If meals were separated by five hours, the first meal should have around 50 g of protein to supply amino acids across that five-hour period. This becomes problematic when we factor sleep into the equation. If this 240-lb. athlete is awake for 16 hours and eats according to hourly protein needs, they will consume just 160 g protein during their waking day. That leaves 80 g to consume before bed, which is more than one-fourth of their daily protein and therefore more than their body can use for muscle production when consumed at one meal. In reality, the one-eighth to one-fourth daily protein total per meal across four to eight meals is sufficiently precise and more practical a recommendation. Hourly calculations might come in handy for those working 24-hour shifts or dealing with other odd schedules in which prolonged periods without sleep occur.

Figure 4.7 The lower curves represent amino acid availability from smaller protein boluses that do not reach the anabolic threshold, represented by the upper wave.

For anti-catabolism, splitting up protein feedings evenly is sufficient. The situation with anabolism might be a bit more complicated, but the consensus in the literature is not quite established on this topic yet. From molecular research, it seems possible that leucine, an amino acid component of most food proteins, is one of the central regulators and activators of muscle growth. If the leucine content of a meal is below some value, the musculature may engage only in anti-catabolism. This hypothetical threshold for anabolism is termed the “leucine threshold” or “anabolic threshold”. What this means is that consuming more protein per meal, even over fewer meals (less than six) might be more effective for muscle gain. There has, as yet, been no evidence from long-term human studies confirming the effect of this threshold, but the molecular evidence is notable. To be on the safe side, consider eating no less than one-sixth daily protein per meal when trying to gain muscle (figure 4.7).