Focus on Protein

[Mitra]

For those who haven't encountered her, Regina Wilshire writes a low-carb blog. She's a self-confessed journal junkie, so is often reviewing the latest findings. In a recent blog, Again it's the Protein (http://weightoftheevidence.blogspot.com/2006/09/again-its-protein.html), she reported on an article in the Sydney Morning Herald (http://www.smh.com.au/news/health-and-fitness/skinniness-gene-imperils-survival-of-the-fattest/2006/09/21/1158431825165.html) that highlighted the importance of protein in weight control. Observations of insects suggested that they'd keep eating until they managed to get the amount of protein they needed. The researchers wondered if humans behaved similarly.
With colleague Professor David Raubenheimer, of the University of Auckland, he devised an experiment to find out if humans did the same. "We incarcerated 10 people in a chalet for six days."

For the first two days they could eat what they wanted from a buffet. For the next two days, one group was restricted to high-protein foods, such as chicken and meat, the other to fatty, sugary, low-protein foods, such as croissants.

The first group consumed exactly the same amount of protein as on the first two days. "The second group went way off the mark and just kept on eating until eventually, through their over-consumption of carbohydrate-rich foods, they managed to fill their protein intake."

Does any of this sound familiar ;)?

[Gabriel Guzman]

Yes it does! :) On a similar note, I just finished reading an article published in the Journal Nutritional Biochemistry (Short-term, increasing dietary protein and fat moderately affect energy expenditure, substrate oxidation and uncoupling protein gene expression in rats, JNB article in press).

In the case of these rats, they were fed different diets with different protein content. The authors refer to 20% of calories from protein as 'adequate protein' (AP), 13%F as 'normal fat' (NF), 64%P as 'high protein' (HP) and 40%F as 'high fat' (HF). To begin with, that may be the case for rats (although I doubt it), but for humans 'adequate' means something completely different. Anyway, basically, different groups of rats were fed combinations of AP-NF, AP-HF, HP-NF, and HP-HF for 4 days (short-term) to see if macronutrient composition would have an effect on substrate oxidation (whether they burn more fat or more carbohydrate) and energy expenditure. Of course, carbohydrates were adjusted accordingly to complete the macronutrient composition and the source was corn starch.

The results were not really surprising as I've seen similar results reported over and over with respect to weight gain. The rats exposed to HP diets gained less weight during 4 days than the other experimental groups. The lowest weight gain was observed in the HP-HF group. Total energy intake, on the other hand wasn't any different from their control group or the group that ate AP-NF. The researchers even considered interesting that the HP-HF group actually consumed less food compared with all other groups.

An interesting result was that when they measured net oxidation of macronutrients, they found that rats eating HP-HF oxidized more fat than any other group, even the groups consuming HF. The groups eating AP-HF, for example, since the amount of carbohydrate was relatively lower (42%), could have been expected to use oxidize more fat. The fact that from the groups that ate HF, only the group that ate HF combined with HP oxidized more fat, suggest a role of protein to enhance fat oxidation.

Since rats are nocturnal animals and they eat most of their food at night, the result that energy expenditure (EE) and resting metabolic rate (RMR) didn't differ between groups was not surprising. However, nighttime EE was higher when related to body weight in the groups that ate HP as compared with controls, and the effect was significant for the HP-NF group. Oxygen consumption (related to body weight) was also higher in the groups that ate HP. As expected (at least to me), the fat content of the experimental diets (between 13-40%) didn't have additional influence on oxygen consumption. I don't see this as surprising because the amount of fat, even if they call it 'high' may not have been really high enough.

Nonetheless, they were able to calculate the respiratory quotient (RQ), which indicates which substrate is being oxidized, whether it is fat or carbohydrate. RQ is actually the ratio of the volume of carbon dioxide produced and oxygen consumed. If RQ is 1 or close, then there is more carbohydrate oxidation (CO) than fat oxidation (FO). If RQ is close to 0.7, then there is more fat oxidation than carbohydrate oxidation. As expected, RQ was lower as the carbohydrate amount decreased in the diets, indicating more fat oxidation. Protein can also be oxidized and the researchers measured more protein oxidation (PO) in the group of rats that ate HP-NF, an effect that was significantly lowered by adding more fat to the diet as they observed from the group that ate HP-HF.

So, thus far, the groups eating HP


gained less weight while having the same amount of energy intake
had higher energy expenditure during their active period (nighttime)
oxidized more fat, effect significantly higher when the diet contained HP
oxidized more protein, effect attenuated when HP was combined with HF


The rest of the experiments (and results), deal with the expression of a special type of mitochondrial proteins called 'uncoupling proteins' (UCPs), which are involved in 'leaking' energy in the form of heat from the mitochondria. Perhaps the most famous is UCP1, which is abundantly present in brown fat and is activated by adrenergic stimulation. The functions of UCP2 (present ubiquitously) are still debated; some believe is a true uncoupler while others say is more involved in other functions. UCP3, present in muscle is also believed to function as UCP1 but that is also debated in some circles. I think the researchers could have approached their study of UCPs in a different way and possibly produced a whole new manuscript just with that so I'm not going to discuss those results.

The take home message, at lest from studying these rats is that there is more to macronutrient composition than just low-this/high-that with respect to fat and carbohydrate content of any diet. In my opinion, it is a narrow view to think on those terms only without adding another important component; protein.

What I take away from this study is that


an increased amount of protein in the diet not only increases energy expenditure
prevents weight gain while providing enough energy intake
when combined with adequate amount of fat and a reduced amount of carbohydrate, fat oxidation is not only favored but enhanced


All of those attributes are very attractive in the context of weight loss, weight maintenance and good health. Whether this is what happens in humans is still a topic for more research, but thus far nutritional studies in humans seem to suggest similar effects of increasing protein in the diet at the expense of carbohydrate, not fat.

[mrballs]

Interesting study but can't this be explained by low insulin. If HP-HF (64/40? like a mortal could sustain this diet) were consumed:1) low insulin=> increases sodium excretion=> increased urination=> short term weight loss (plus wouldn't 64% protein lead to diarrhea?). 2) low insulin=> glucose depletion=> fat becomes skeletal muscle energy source=>ketosis=> appetite suppression and lower RQ quotient. For HP-NF perhaps a low fat diet increased anxiety (physiol behav,sept1,1996 60(3):039-42)=> increased energy expenditure as I have seen studies before that have claimed low fat diets increase anxiety. Lastly, I have seen lots of studies that show high protein diet suppresses appetite but for the common man it is a difficult diet. I have eaten ~28/13/58 prot/carbs/fat on 3300 daily calories ( which amts to over 230 grams of daily protein) for the last 2 months and would find it to be great suffering to increase that amt.

[Gabriel Guzman]

Actually 64/40 is neither inconceivable nor impossible if the amount is set according to individual needs (for use that means size and level of physical activity). Without measurements of insulin we can't say anything about it, at least not in that study. Studies in humans, on the other hand, have shown better postprandial insulin response when the ratio protein/carbohydrate is high (i.e. more protein and less carbohydrate in the diet). In the study mentioned above there was no mention of weight loss but less weight gain, which is different. So we may be talking about different things here when trying to link changes in insulin and the results presented.

A decrease in carbohydrate intake, which comes with a decrease in insulin secretion, favors the use of fat for fuel, but what is interesting in that study is that fat oxidation was enhanced only when protein intake was also higher. So, a decrease in insulin alone cannot explain an enhanced fat oxidation under 'adequate' protein. Nonetheless, a decrease in circulating insulin is a desireable effect of any dietary intervention as it sets the optimum scenario for beneficial changes to take place, such as the use of fat as the main source of fuel, release of excess sodium, etc. After that, something else is needed to keep the metabolic advantage and a higher protein intake seems to accomplish that.

There is really no such thing as 'glucose depletion' when insulin levels are decreased. When needed, the liver responds making more glucose from non-carbohydrate sources. Since ketosis wasn't measured either, is hard to say anything about decrease appetite and ketosis. Again, in humans, there have been reports of association between ketosis and decrease appetite just as there have been reports of no association. It's hard to adscribe causality between ketosis and appetite suppression. Higher (not necessarily high) protein intake, on the other hand, is associated with higher and longer postprandial satiety, which is not the same as appetite suppression, whether ketosis was detectable or not. By the way, how would a higher protein intake induce diearrhea? Just curious... I haven't read anything about that before.

Regarding higher protein intake and satiety, studies in healthy and diabetic humans suggest that even a modest increase in dietary protein has an impact on postprandial satiety. In humans is hard to talk about a truly 'high' protein diet. Anything about the recommended 15% of calories from protein (which is not very much) is higher. So, is 30% of calories from protein a 'high' intake or just higher? Contrary to what the main stream experts say or think, increasing dietary protein intake up to 30% of their calories in diabetics didn't cause damage in any way but improved their insulin homeostasis.

I'm also curious as the way you determined that you need 230 g of net protein daily as well as the need for 3300 cal/day. The standard calorie rule fails when one tries to structure a nutritional compositon based on adequate protein that is limited in carbohydrate and moderate in fat (i.e. Protein Power-like). One of the reasons is that the daily caloric intake considers body weight instead of lean body mass. Although it doesn't sound too much of a problem, when it comes down to numbers, once could find a significant overestimation in the amount of daily calories. I discussed this very issue in a previous post a few months ago:


On a low carbohydrate diet, which produces adaptation to fat as the preferred source of fuel, the standard calorie rule doesn't apply unless you correct for the respiratory quoficient to estimate BMR. That alone changes the amount of calories needed as 'basal'. The 'normal' way to estimate BMR considers only body weight and could either underestimate or overestimate the amount of calories if a person is very muscular of very overweight, respectively. A more accurate way to estimate BMR is to account for the caloric equivalent of the nutrients, and it is here where it matters a great deal if a person's diet includes more fat, protein or carbohydrate. Even then, standard methods to estimate metabolic rate assume that the portion of protein in the diet is fairly constant, which may not be the case. Nonetheless, and keeping that in mind, it is possible to estimate metabolic rate by multiplying the caloric equivalent times the respiratory quotient (RQ). RQ, which is an indication of how much oxygen is being used is largely influenced by the composition of macronutrients and is higher when more fat is used for energy. Hence, the RQ when the substrate for energy is mainly fat, as it happens on a low carbohdyrate diet, is significantly smaller compared to the RQ when energy is produced mostly by using carbohdyrates.

The RQ when the substrate for energy is mainly carbohydrate is 1.00, hence the importance of considering that when talking about estimations of BMR. Therefore, without that consideration, BMR calculations could be overestimated up to 25% and you can carry that overestimation all the way to the calculation of basal caloric needs since to do that, according to the standard calorie rule, you multiply your BMR times an appropriate activity factor.

The standard method to estimate BMR, the Harris-Benedict formula, which by the way was published in 1919 when there were fewer people in the world, accounts for gender, age, height and weight appears to be reasonably accurate for normal people with normal body fat. Given that there were far fewer obese people around back in the early 1900s than there are today, we should always be aware of this weakness. If we used lean instead of total body weight, we could presumably compensate for the weakness of the formula. The actual BMR would thus be related to fat-free mass and then to estimate caloric needs, we would multiply that lean body mass-related BMR times the appropriate activity factor. On a low carbohydrate diet, most of the energy comes from fat utilization and since the aim of weight loss or maintenance is not to sacrifize muslce protein, then it makes perfect sense to estimate calories in terms of lean body mass, which in other words means estimate the amount of protein needed to maintain such mass, which in turn strongly suggests where those calories should come from. What muscles need is mainly protein, not carbohdyrate.

The focus, again, seems to be protein rather than fat or carbohydrate, aiming to an adequate protein/carbohydrate ratio. When adequate protein is ensure, whatever the amount of fat that comes with it (including good quality fat from vegetable sources) turns out to be 'moderate' and not likely to be in excess. If the findings of the study in rats hold true for humans (and thus far that seems to be the direction), a higher protein/carbohdyrate ratio would set the metabolic scenario for more fat utilization (for fuel) while the higher intake of protein may enhance fat oxidation. Together with the other effects of increase dietary protein (higher satiety, increase thermogenesis, better postprandial insulin response) this may help keeping the much desired metabolic advantage (or caloric deficit) always 'on', not only to achieve weght loss but also weight maintenance and overall good health.

Thanks for the discussion!

[mcsblues]

Higher (not necessarily high) protein intake, on the other hand, is associated with higher and longer postprandial satiety, which is not the same as appetite suppression ...

Hi Gabe,

Do you have a definition which distinguishes appetite suppression from satiety?

[Gabriel Guzman]

As far as I know, centrally acting appetite suppressant drugs used in the treatment of obesity fall into 2 broad pharmacological categories; those which act via brain catecholamine pathways and those which act via serotonin pathways. Whether protein acts via one of those is debatable but the main difference is that appetite suppression needs to happen before food intake thus reducing food consumption. Depending on the compound, the effect is achieved either by inducing a feeling of fulness (one of the subjective ways of measuring satiety) and/or inducing feelings of nausea or even a side effect of malaise.

Satiety caused by protein intake doesn't depend on a pre-induced state of fullness as appetite suppressants do. In fact, the perceived fullness comes after protein intake and lasts long enough until hunger sets in again.

Appetite suppression and satiety may sound conceptually identical but the mechanisms may be quite different. Perhaps the difference is more a practical one. Nonetheless, appetite is an interest in eating, and we can have appetite even if we don't require food. That seems to be the case when the diet contains excessive amount of sugary foods. Alternatively, we could be physically hungry but without interest in eating (signs of hunger include stomach rumbling or even a little pain, irritability, feeling lightheaded). Physical hunger, defined as the body asking for food, may not correlate with appetite. A compound that affects the appetite centers in the hypothalamus, for example, may suppress the interest in eating but nut necessarily hunger. After a full meal, on the other hand, even though we may have met the necessary amount of nutrients to suppress our physical hunger, we may not have suppress our interest in eating (appetite). Perhaps that explains a bit why even after a meal witha nice 12-oz steak, salad, and perhaps a roll, we still find room for dessert:) An extended period of feeling 'full' seems to be the commond denominator when the meals are protein-rich.

[mrballs]

From the study. Protein/fat/carbs grp 1)AP-NF 20/13/67
2)AP-HF 20/40/40
3)HP-NF 64/13/23
4)HP-HF 64/40/-4 (?) Results=> A) 3+4 gained the less weight with 4) eating less. B) Net oxidation, 4) oxidized more fat than any group w/c according to the colorado state u website says, "..insulin drives most cells to oxidize carbs instead of FA's..." Since diet 4) has no carbs=> less insulin in blood=> more oxidized fat. But u say that this suggests a role of protein to enhance fat oxidation? and "...fat oxidation was enhanced only when protein intake was also higher." I no understand how u made this conclusion. ( I could see if 50/50/0 vs 40/60/0 vs 30/70/0 groups showed decreasing oxidation then I may agree that protein is enhancing oxidation) Also wrt glucose depletion. Since amino acids coverting to glucose cost ATP's and liver must rely on O2 metabolism to replace ATP's => And since the liver gets most of its O2 from the portal vein where partial pressure of O2 is low=> low ATP synthesis=> low glucose production from amino acids. 400 grams of glucose per day max says this dude on the rabbit starvation site and 160 grams per day consumed by a sedentary person, are you saying glycogen doesn't deplete? I mean unless one is burning 100% fat it would appear to me that one would quickly deplete the glycogen stores even with a minute amt of exercise. Please enlighten. Lastly, I think 60% protein would overwhelm one's digestive enzymes similar to lactose does lactase. As far as the diet i keep, its mostly because I"M HUNGRY. I am considering dropping weight classes and must get down to 242lbs (powerlifting no juice though). I tried to up the protein to sate the appetite but it appears not to be working. Cant seem to fit anymore protein in the diet. Have maintained a bodyweight of 255-253 on 3300 calories now for 2 months even with the starting of creatine. I look forward to your reply. Thank you in advance.

[Gabriel Guzman]

See the graphs. That will help you. The graphs that show how different nutrients were oxidized show higher oxidation when the diet was HP-HF.

Regarding protein overwhelming diggestive enzymes, I'd like to see data on that.

Lastly, have you ever composed your diet calculating your protein intake based on your lean body mass and level of physical activity? So far you've said that your calories are 3300, which I assume you estimated based on the standard way of doing, not considering carbohydrate restriction. It woudl seem that you may be underestimating your level of physical activity (since you do lift weights) and are trying to meet some number of calories.

For example, let's say that you estimate your body fat percentage, which gives you the actual fat weight in your body. When you subtract that from your total body weight you get your lean body mass, which includes muscle, bone, liquid, and proteins that are not muscle protein. However, it's safe to assume that most of your lean body mass is represented by your muslce mass. Now, knowing your lean body mass, then let's say that you are engaged in regular and vigorous weight lifting, which means a high level of physical activity. The higher your level of physical activity, the more protein per lb of lean body weight you need. That is only to supply the necessary amount of protein just to keep your lean body weight and you do want to keep it as it is highly metabolically active, which in turns helps to get rid of unwanted body fat.

So, let's say again that because your level of physical activity is high, you need 0.7-0.8 gr protein/lb of lean body mass. If you multiply your lean body mass by 0.8, that will give you the amount of protein you need per day to supply just to keep your lean body mass. That will be your minimum protein intake, which means you can always eat more than that (together with other foods of course!). If you set your carbohdyrate level to whatever level you want to be (in Protein Power that is), let's say 55 gr ECC per day (made up from fibrous vegetables and fruits that are good carb-bargain), the final amount of calories you will end up will be far less than 3300... I could almost bet on that. However, the food you're providing is exactly what your body needs because is tailored to your individual size and level of physical activity.

You might want to consider this kind of approach and see how it works for you.