13 01 2013
The High Protein Diet
As diets go we’ve seen our share. Since the beginning of the obesity epidemic there have been a ton of dietary fads and quick-fix diets, the majority of them with the same outcome. The epidemic keeps spreading exponentially, and while many of these diets help people lose some weight short term, they quickly gain it back as soon as they stop the diet. And they DO eventually stop the diet, because most of these diets are hard to maintain due to inconvenience or lack of palatability. What surprises me in all this is the extreme focus on increasing or decreasing various forms of fat and carbohydrate, while relatively little focus is placed on the protein content per se, while research repeatedly demonstrates the importance of protein in reducing body-fat and preventing weight regain after a diet. In the mean time, as far as fats and carbs are concerned, few people know what to think anymore, and many have an irrational fear of fats and carbs that is, if anything, making newer diets even less palatable and harder to maintain.
The obesity epidemic
Overweight and obesity can be the result of any or a combination of genetic, social, behavioral and environmental factors (1). However human genetics haven’t changed the past decades, and the absence of weight problems in these proportions in populations that don’t follow our lifestyle, have made it easy to single out our poor dietary choices and lack of physical activity as the main culprit for a condition that is placing a burden on our health care costs the likes of which we have never seen. Obesity gives rise to increased incidence of cardiovascular problems, as well as metabolic problems, not in the least of which type 2 diabetes, and research has repeatedly indicated that weight management alone can reduce those risks drastically. 34% of Americans suffer metabolic syndrome, and the prevalence reaches as high as 50% with age (14). Aside from that, increased body-fat as well as reduced bone and muscle mass due to inactivity, are combining with our increased life-expectancy to give rise to another epidemic, namely sarcopenia and osteoporosis, two conditions that impair the mobility and quality of life later in life, giving us a population that has never been as old or unhealthy as it is now, and is crippling our economy.
We’ve also never looked as bad as we do today, as a population. Beauty is in the eye of the beholder, true, but one thing remains constant in aesthetics : the rarer it is, the higher it is valued. In the time of Rubens, plumper women were considered more attractive, because they were rare, and their weight was a sign of their status in life, and their means. Nowadays very low body-fat percentages are considered most attractive, because overweight has become commonplace, and a fit body demonstrates qualities absent in the masses : will-power and determination. The good news is that attaining will-power is still more manageable than increasing your means.
The thing is we are genetically prone to consume and conserve energy as much as possible to ensure survival. We were just stupid enough as a society to place ourselves in a position where this will become our greatest threat to survival, with some sources predicting this will be the first generation in 3 centuries to have a shorter lifespan than the preceding one. The main difference between this day and age and the time before the epidemic is that we no longer HAVE to move or want for food. And our genetics are doing the rest.
The (lack of) importance of fats and carbohydrates in the diet
Increased intake of fats is certainly one key factor, if not the most important one, in the rise of the epidemic. Fats contain more calories than protein and carbohydrates (9kcal as opposed to ~4 kcal per gram). Early efforts to reverse the trend of weight gain focused largely on decreasing calories in meals by reducing the intake of fats, but the outcome was completely opposite of what was expected, because they underestimated the importance of satiety. As long as we are in a position to consume food whenever we want, hunger and desire are the prime motivators for eating more. Reducing the fat content of our diet also reduces satiety, which only increases overall food intake to compensate. That in turn sparked a counter-reaction leading to some adopting a relatively high fat diet in order to increase satiety. However fat source plays a key role as well, and it is hard to maintain a diet rich in healthy fats because not everyone finds nuts and oils extremely palatable. At the same time most people have a hard time estimating the caloric content of high fat meals, leading to an overconsumption of calories as well. One should certainly consider increasing ones healthy fat intake, and if possible at the expense of carbohydrates (2), but beyond that modulating the intake of fats will only needlessly complicate matters. Carbohydrates are in the same boat. The second most important factor in increased obesity is the increased intake of refined sugars like sucrose, glucose, maltodextrin and high fructose corn syrup. These factors cause large spikes in insulin, and while insulin is also an important factor in satiety, the fast and transient nature of these insulin spikes leads to low blood sugar not long after which has an opposite effect : energy stress and increased hunger. That too led to a whole variety of diets based on a low-carb principle. What those people seem to forget is that our sedentary society has lived on a high carb diet for well in excess of 2000 years and never suffered obesity. The difference was only the source of the carbs, and the absence of refined sugars. Research shows that there is statistically no difference between high and low carb diets in terms of weight lost (3,4,5). There is potential benefit in an extremely low carb diet, called the ketogenic diet, because such a drastic absence of carbohydrates leads to very high gluconeogenesis and ketone formation out of amino acids, both energy intensive processes, to replace glucose, but again, such diets are extremely hard to maintain for longer periods of time and drastically affect a person’s mood and behavior. Beyond that, again, short of avoiding refined carbs, there is very little benefit to be had from modulating carb intake per se.
What will happen on a high protein diet of course is that both will be reduced partially to make room for increased protein intake. But that is the key point of this article, namely that the high protein content and not the content of carbohydrates or fats is the key determinant of the effects of the high protein diet.
Protein and bodyweight regain
The major problem with curbing the obesity epidemic is preventing bodyweight regain. Plenty of diets have shown some degree of effect, mainly because of two factors. The first is that any change of diet creates a period of adaptation for the body, and the second is that the simple basis of weight loss is that the number of calories ingested is smaller than the number of calories expended (6). No matter how you twist or turn it, 90% of your diet is as simple as that. If calories expended exceeds calories ingested, the extra energy to compensate needs to come from somewhere, and the result is a decrease in bodyweight. However when such diets cannot be maintained, they offer no alternative, and when the diet is ceased, weight is quickly regained as people relapse into their old habits. The approach to reverse the relapse is based on increased satiety despite a negative calorie balance (preventing yourself from eating more because you always feel hungry), sustained resting energy expenditure in the face of decreased bodyweight and, closely related, the retention of fat-free mass (since this determines resting energy expenditure, and forces a greater reduction in bodyweight from fat mass). Increased dietary protein has been shown to aid in all three of these factors (7,8,9,10,11).
Protein and satiety
A high protein diet seems to have a much more satiating effect than a diet rich in fat, and significantly more than one rich in carbohydrates (5,12). As early as 1956 (13) it has been shown that elevated concentrations of amino acids in the blood beyond that required for protein synthesis serves as a satiety signal and results in decreased energy intake. So while there is absolutely some truth that we can only use a certain amount of protein to fuel protein synthesis at any one time, as this article will make abundantly clear, that does not mean there is no use for increased protein beyond that point. This also explains why whey seems to be more satiating than casein (14) despite a similar amino acid profile. Because of the slower digestion, the blood amino acid level would rise slower due to greater distribution over time. But similar to insulin (but less drastic due to less effect on energy stress following lowered blood amino acid levels compared to lowered glucose levels) a large spike can be more satiating short term, but not necessarily long term, making it important to work with combinations of fast and slow proteins to produce the longest effect on satiety. The precise mechanisms behind the stronger satiating effect remain elusive at this point, since protein seems to have no effect on anorexigenic (hunger-reducing) peptides upon ingestion (15). The larger satiating effect from animal sources of protein like dairy and meat compared to lower quality plant sources (soy, rice, hemp, pea) (11) can probably be explained by the increased insulinogenic effect of higher quality protein, but would not explain why protein at large is still more satiating than carbohydrates.
Protein, fat free mass and energy expenditure
Aside from satiety, the principle way in which the high protein diet seems to facilitate weight management is in its effect on fat free mass (FFM) and energy expenditure. Energy expenditure can be divided in three categories, namely resting energy expenditure (REE, also called basal metabolic rate or BMR), Dietary Energy Expenditure (DEE, also called the thermic effect of food or TEF) and the energy expenditure from activity. The latter can obviously only be affected by increasing activity, and stresses the importance of exercise (see addendum later on). But increasing the other two forms of energy expenditure would result in a higher use of calories without needing to increase activity, and thus provide a fairly effortless way to improve caloric balance in your favor. The basis of it all starts with the effect of protein on sparing FFM however. When one applies caloric restriction, weight is lost, but it is lost equally from muscle and adipose tissue. If one can create an effect that spares muscle, we not only procentually increase the weight lost from fat, the kind we’d prefer to lose, the relative increase in FFM is also a key determinant of REE, since unlike fat, muscle is a metabolically active tissue that requires energy, and thus calories to maintain. Under normal conditions a normal protein intake (minimum of 0.8 g/kg bodyweight) will cause muscle protein synthesis after feeding, but similarly muscle protein is lost during the periods between meals, so that your dietary protein ends up replacing what is lost. However if we equally reduce calories from all three macronutrients, we obtain a reduced capacity for protein synthesis so that we cannot adequately replace what is lost. From this alone it becomes evident that maintaining a relatively high protein content when reducing calories will have a greater effect on sparing FFM. Remember, this isn’t even a true high protein diet, you are just maintaining sufficient protein intake on a hypo-caloric diet, resulting in relative increase in percentage calories from protein in your total diet. From previous articles you already understand the importance of eating more than the bare minimum of protein in order to maximize protein synthesis (and have an even greater degree of FFM sparing), and from the previous paragraph you already know that it takes an increase in blood amino acids beyond the point of maximizing protein synthesis to induce maximal satiety. Now, the common bodybuilding recommendation of 2.2g per kg bodyweight is probably more than we can use at any given time, so one shouldn’t be overly concerned if one doesn’t reach that point during a diet (1.5-2g/kg should be more than sufficient), but it does strongly stress the importance of an absolute high protein diet to get the most benefit for both muscle gain and fat loss. One reason REE is boosted on a high protein diet, aside from the increased calorie usage of muscle at rest (which is sadly often overestimated) is the energy cost of protein synthesis. One study (16) postulated : “Assuming the energy cost of protein synthesis is 3.66 kJ/g and the baseline GAIA-derived lean tissue mass was 56.4kg for EAAMR (essential amino acid meal replacement) and 54.4 kg for CMR (competive meal replacement, ie the control) equivalent to 27170 kcal for 3.5kg of weight loss across the entire caloric-restriction based weight loss paradigm.” This quote is of course based on a linear progression based on the findings of that study and should be taken with a grain of salt, but it adequately demonstrates that across a diet lasting 8 weeks, the relatively high protein meal led to a difference of 3.5kg in weight in this particular study, on average. So it seems that the anabolic effect of protein on muscle protein synthesis may be a key determinant in its increasing REE. This previously also described in the Stock Hypothesis for body-weight gain (23), based on a study from 1999 demonstrating that building FFM requires an average extra energy cost of 52 MJ/kg bodyweight, where building a normal proportion of FM and FFM requires only 30 MJ/kg.
Dietary energy expenditure (DEE) is basically the cost of eating, or a percentage of calories that is expended to process the food you ingest. Here too there is a large difference between macronutrients, with protein yielding a DEE of 20-30% where carbs only yield 5 to 10% and fats as low as 0 to 3% (4). That means of every gram protein you eat, 20-30% is immediately metabolized, and doesn’t really count toward the caloric value based on REE. Or in simpler terms : eating more protein burns more calories. The most likely reason for increased REE lies in its effect on gluconeogenesis, or the creation of glucose from amino acids, mostly alanine and glutamine. When comparing a high protein- carbohydrate free diet to a moderately high carb, lower protein diet, 42% of the increased energy expenditure was attributed to increased gluconeogenesis (with the remainder probably being attributable to ketogenesis since it was a carbohydrate free diet) (17,18). Now one could attribute this to the lower carb content, but in a hypo-caloric high protein diet there will be significant degree of gluconeogenesis to compensate for lack of energy regardless. That also explains the bigger effect of high quality animal proteins(11), since those proteins are incredibly dense in alanine and glutamine, particularly dairy and meat proteins (up to 25% of total amino acid content)
Sustaining a high protein balance on a diet for several days also affects sleeping metabolic rate (SMR) (19,20). The effect again was more pronounced with a complete protein (casein) than an incomplete one (gelatin). Because it concerns REE while sleeping, it is at this point unknown whether this is attributable to the same factors (increased Protein synthesis and FFM), but given the difference between sources, it seems likely.
Addendum : the role of resistance exercise
A brief addendum that for some reasons I seem to be adding to nearly every article, is the importance of resistance exercise in accentuating these effects. Because resistance exercise increases Muscle protein synthesis for periods up to 48h (21), the periods of protein synthesis after protein feeding are accentuated and the periods of protein loss during fasting are attenuated (22). This results in a greater protein accrual during caloric excess, and a greater protein retention during caloric deficit. As a result you cause a favorable shift of nutrient use toward muscle, and given the previous data, a greater caloric expenditure, so that less fat is gained on a caloric excess, and more fat is lost on a caloric deficit.
Resistance exercise, just like a high protein diet, seems to also play a crucial role in preventing aforementioned epidemics of obesity, sarcopenia and osteoporosis, to such an extent that a recent issue of Harvard Health recommended resistance exercise to the population at large (24) for general health and a better quality of life at a later age.
The net result : Body recomposition and nutrient repartitioning
These are two terms you’ve probably heard mentioned a thousand times, and in 999 of those cases it was probably not truly applicable. That is because resistance exercise and a high protein diet are in fact the only two known body recomposition and nutrient repartitioning agents known to us. Body recomposition implies a change in the location of weight. The best way to explain it would be to have you look up people on a dating site. When you come across a gentleman who is 6 feet tall and weighs 200 lbs, chances are good you won’t find a great physical specimen, or even a healthy one for that matter. Yet the professional fitness models that grace the cover of Men’s health every month will typically have those same stats. The difference is that they of course have more muscle and significantly less fat. It stresses that not weight is important in health and looking good, but rather what kind of weight. Nutrient repartitioning is creating an effect where tissue distribution of nutrients after ingestion is altered to favor one tissue rather than another, in our case the ability to increase muscle growth or retention, and limit fat gain or maximize fat loss. Most any factor in diet or supplements, short of protein, however, largely affects fat mass the same way as muscle mass.
The take home message : Keep protein high for best results, and don’t stress the rest
Establishing and accepting that the benefit of a high protein diet comes from the fact that is high in protein, and not worrying about carbohydrate and fat intake, short of possibly replacing refined carbohydrates with healthy fats where possible, not only makes things a lot easier, it makes diets a lot more manageable. The irrational fear of carbohydrates and fats is just that, irrational. The experimenting with such conditions first started as a reaction against increasing obesity, and 30 years down the stretch, we are still dealing with increasing obesity. And yet before the obesity epidemic we consumed a high carbohydrate, moderate fat diet as well. It is crucial to identify and recognize the causative factors of our poor lifestyle and ameliorate them, but those do not extend further than severely limiting refined carbohydrate intake (not carbohydrates at large) and making sure we get ample “healthy fats”. The parenthesis are there only to emphasize that we call them healthy because we don’t get enough of these and too much of the other kind, not necessarily that one is more important than the other. But in the mean time increasing the absolute protein content of your diet will be bigger factor in determining your success with muscle gain, fat loss and preventing fat regain after a diet.
Even for athletes who understand the importance of protein sometimes the focus is entirely too much on carbohydrates, and without any real reason. When preparing meals for a fat loss diet one should be primarily concerned with making sure under the necessary caloric restriction that protein remains high, more than any other type of modulation. That’s why at 4 weeks out, I’m still snacking on the stuff in the recipes section, instead of grudgingly staring down a Tupperware container of chicken and broccoli. Protein cooking and increasing the protein density of meals is by far more beneficial to the final result, and the presence of ample carbs and fats just makes meals more palatable adherence to the diet more likely. Obtaining a lean physique takes hard work and determination, so why make it harder on yourself than you have to ?
And the high protein diet is for everyone, all the time. And it’s simple to implement. Increase protein intake to 1.5g/kg lean bodyweight or more, reduce your intake of refined carbohydrates (which is easily done by limiting your intake of processed food as a whole), and maintain a balanced, moderate fat intake. For most people that last part means increasing once intake of unsaturated fats (and especially omega-3’s), and decreasing ones unsaturated fat intake. Such a diet is the most efficient way to lose fat, prevent body-weight regain after a hypo-caloric diet and to gain the maximum amount of lean mass while restricting fat gain on a hypercaloric diet, in combination with a resistance training regimen.
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