Is it possible to eat too frequently?

It's not uncommon to read about bodybuilders or otherathletcs taking the cat-more-frequently dictum is the idea that optimal results should occur by maintaining a near continuous influx of nutrients into the body. I imagine if they could find a way to do it, some enterprising athletes would set up a continuous intravenous drip with carbohydrates, amino acids and essential fatty acids.

This may not be a good idea in the first place. Some research, primarily using amino acid infusion, suggests that skeletal musclc can bccomc insensitive to further stimulation of protein synthesis. In one study, amino acids were infused for several hours to 70% over normal levels (17). Protein synthesis increased after roughly 30 minutes and was maintained for the next two hours at w'hich point protein synthesis decreased back to baseline.

Importantly, this decrease occurred despite the maintenance of high levels ofblood amino acids. Additionally, there w'as an increase in urea production (a waste product ofprotein metabolism), indicating that the excess AAs were simply being catabolized in the liver to be excreted in the urine; that is, those AAs were wasted and never utilized by the musclc.

The researchers took this as a suggestion that there might be a maximum amount of protein synthesis that can occur at any one given time before a "muscle full" situation is reached (18). Perhaps more interestingly, based on the amounts of AAs infused, the researchers estimated that only 3.5 grams of AAs would be required to result in this "muscle full" situation (18). I want to make it very clear that this doesn’t mean that 3.5 grams of orally ingested AAs would cause the same effect. Rather, this represented the delivery of 3.5 grams of AAs to the musclc itself.

However, the total amount of dietary protein to achieve this amount wouldn't be huge. Most dietary proteins arc roughly 40-50% EAAs, and due to processing in the liver, slightly less than half ofthe ingested AAs actually make it into the bloodstream. To provide 3.5 g EAAs to skeletal musclc would require roughly 15-20 grams of whole protein over a two hour time span.

Interestingly, other more direct research supports this value. In a study I described in an earlier chapter, subjects received doses of EAAs ranging from zero to 20 g EAAs and protein synthesis w'as studied (19). In young subjects, musclc protein synthesis w'as maximized with an intake of 10 g EAAs and there was no further increase w'ith 20 g EAAs. This represents roughly 20-25 grams of whole protein.

Consumed every three w'aking hours (roughly six meals per day), this would allow* for a maximum protein intake of 120 grams per day before skeletal muscle protein synthesis is maxed out. For a 100kg (220 pound) athlete, this is only 1.2 g/kg, lower than even the most conservative estimates discusscd in Chapter 4. As discusscd previously, this research is a difficult to reconcile w'ith other, much higher recommendations or empirical results.

However, recall from Chapter 4 that dietary protein has more functions for athletes than simply the stimulation ofprotein synthesis. Although the amount described above might very well maximize skeletal muscle protein synthesis, optimizing the function of other important pathways of AA metabolism would very likely raise requirements even further (20). As well, w'hile excess amino acids may simple be oxidized off, there is evidence that increased AA oxidation is involved in the overall "anabolic drive” ofthe body.

Finishing up this discussion, in their most recent study, the .same group examined the cffcct on protein synthesis of a variety of doses of infused AAs (21). Infusing AAs at four different ranges, the group saw' a similar pattern to their earlier w'ork, an initial increase in protein synthesis followed by a return to baseline despite maintenance of high AA levels.

Additionally, while the lower infusion rates caused a significant increase in protein synthesis, further increases at the higher concentration levels showed smaller additional benefits. Essentially, providing low to moderate amounts of AAs gave the greatest result.

Finally, and perhaps most interestingly, the paper demonstrated conclusively that it was extracellular AA concentrations (rather than the concentration of AAs inside the muscle ccll) that were involved in stimulating protein synthesis. The researchers suggested the existence of some type of amino acid "sensor" in the musclc ccll membrane that sensed AA levels. The study also suggested that it was the changes in extracellular AA concentration, rather than the absolute amounts that were driving the changcs in protein synthesis. That is, it was the change from lower lo higher that had the effect more than the absolute amount of AAs present.

Along with the indication of a "resistance" to further stimulation of protein synthesis, it appears that raising AA concentrations (after a meal) followed by a decrease in concentrations yield the best results. Basically, spacing meals apart and allowing blood AA levels to drop, rather than maintaining AA concentrations at continuously stable levels, appears to have the greatest impact on protein synthesis. Unfortunately, this still gives no indication of how far apart those meals need to be spaced to allow a "rcscnsitizalion" of the musclc lo a subsequent increase in AA concentrations.

Additionally, since it was based on an amino acid infusion, it's unclear how this would relate exactly to the consumption of meals. Between digestion and the hormonal response that occurs with eating, it may very well be that eating protein would yield a different result than what the above research found using AA infusion.

In this vein, it's interesting to look back at the original casein versus whey research that I discasscd in Chapter 2. In that study, whey protein showed an initial spike in protein synthesis followed by an increase in amino acid oxidation in the liver, a pattern not dissimilar to the work examined above (22). It seems plausible that once whey had maximally stimulated protein synthesis, the remaining AAs were simply metabolized in the liver.

In contrast, when very small amounts of whey (a few grams at a time) were sipped over a six hour span to mimic the effects of casein, there was no increase in amino acid oxidation (23); however the impact on protein synthesis was also smaller. It may very well be that flooding the body with large amounts of AAs simply overloads the muscle's ability to utilize amino acids, causing the excess lo be burned off. This would also be consistent with the fact that the slower protein, cascin, actually generated a higher overall gain in Icucinc in the body compared to whey; by never overloading the body’s protein synthetic machinery, overall better results were obtained.

Related to the above research, another group compared the body's use of Icucinc wilh subjects either given small hourly meals or three separate meals (24). They found thal prolein oxidation was decreased (by 16%) in the group given three meals. Essentially, providing amino acids too frequently appears to decrease the body's utilization of those aminos. Rather, having discrete meals where blood amino acid levels first increase (stimulating protein synthesis without overloading the body's ability to utilize AA's) and then decrease for some time (so that muscle can become "sensitive" to the eflcct of aminos again) would seem to be ideal.

At this point it would appear that eating loo frequently (less than every three hours) has no real benefit, and could possibly be detrimental due to the muscle becoming insensitive to the impact of amino acids. It's interesting to note the preliminary report above which found increased LBM gains with three versus six meals per day. Perhaps by spacing the meals further apart, greater stimulation of protein synthesis occurred when protein was eaten.

For the remainder of this chapter. I'll take three hours to represent the minimum amount of time that should pass between meals. Hating more frequently is unlikely to be beneficial and may very well have a negative effect.

How long does a meal maintain the bod/ in an anabolic state?

Having looked at the possibility that eating too frequently might actually be detrimental (or at least not particularly beneficial) given how long a typical meal takes to digest, I want to look at how' long a given meal might possibly maintain an anabolic state.

Mentioned above, considering the relatively slow rate of protein and other nutrient digestion, it appears that even a moderate sized meal maintains an anabolic state for at least five to six hours (8). Individual whole food meals are still releasing nutrients into the bloodstream at the 5-hour mark (7). Very slowly digesting proteins such as casein may still be releasing AAs into the bloodstream seven to eight hours after ingestion (22). Considering this research, we might set a conservative limit of five hours as the absolute longest time that should pass between eating some source of dietary protein during waking hours.

Summary: Theoretical examination of meal frequency

It appears that eating too frequently could potentially be detrimental to the goal ofgaining muscle mass in that muscle tissue becomes insensitive to further stimulation by amino acids, increasing protein oxidation in the liver. Hating more frequently than every three hours would seem to not only be unnecessary (based on the rate of digestion of whole proteins) but could possibly be detrimental.

Given a moderately sized whole food meal, the body w'ill generally remain in an anabolic state for at least five to six hours (and possibly longer depending on the foods chosen). Conservatively, we might use five hours as the upper limit cutoff for time between meals.

This yields a duration between meals of anywhere from three to five hours. This should keep the body in an overall anabolic state without causing problems related to too frequent or too infrequent consumption of meals.

Full time athletes w'ith time to eat very frequently arc probably best served with the higher meal frequency simply to ensure adequate caloric intake. Again, smaller individuals with lower total energy intakes may want to use slightly larger meals eaten slightly less frequently for practical reasons. Similarly, individuals who work jobs and are unable to fit in a meal every three hours needn’t w'orry obsessively about becoming catabolic. A solid food meal containing a high quality protein, carbohydrates, fat and some fiber eaten every five hours will maintain an anabolic state readily.

Protein distribution throughout the day

Related to the topic of meal frequency is the question of whether the day’s protein should be spread evenly throughout the day, or if some other pattern of intake might be superior.

As discussed above, one early study examined whether providing 25% of protein at breakfast and lunch and 50% at dinner had any impact on nitrogen balance compared to spreading the protein evenly across the day’s three meals: no difference was found (9).

More recent work has examined a dietary strategy called "protein pulse" feeding. With that approach, 80% of the day's protein was given at lunch w'ith only 10% at the other two meals: this was compared to a "spread” pattern where the day’s protein intake w'as distributed evenly across four meals. In elderly women, the "pulse” pattern led to a greater protein gain compared to the "spread” pattern (25). However, in younger women, the "spread" pattern w'as superior and led to a greater nitrogen balance (26).

There is a substantial and increasing amount of data that putting some amount of the day’s protein around training is beneficial, a topic that is discussed in detail in the next chapter. Outside of ensuring adequate protein before, during and after training, there is no real indication that distributing the day’s protein in any pattern other than a basic spread pattern is beneficial (again, except possibly for older individuals).

So, for example, take an athlete w'ho will be consuming 200 grams ofprotein per day with 40 grams of that placed around training. That leaves 160 grams of protein to be evenly distributed across the day’s other meals. With a four meal per day frequency, that yields 40 grams ofprotein per meal: at six meals per day, the athlete would consume roughly 27 grams ofprotein at each meal.