Category Archives: Diets - Page 14

Protein, Satiety, and Body Composition

Posted by on January 25, 2011 62 comments

A number of studies have found protein to be the most satiating macronutrient, with fat moderately satiating, and carbs least satiating.

Thus, when people reduce carbs and increase protein, their appetite declines and they almost always reduce calorie intake. This can leads to rapid short-term weight loss. This is why most popular weight loss diets are high in protein: increasing protein causes dieters to quickly lose some weight, encouraging them to continue.

A 2005 editorial in the American Journal of Clinical Nutrition summarized the evidence that higher protein intake is helpful for weight loss:

The higher than usually recommended protein content of many popular diets, such as the Atkins Diet, The Zone, and The South Beach Diet, seems to point at possible solutions to the obesity epidemic. Many national dietary guidelines have, until recently, recommended that only 10–20% of the calorie content of the diet come from protein; however, 30–40% of the calorie content in the aforementioned diets comes from protein, at the expense of carbohydrates. Newer research indicates that the high-protein content of these diets may actually be the reason for their partial success in inducing weight loss, despite no restrictions in total calories (2)….

In this issue of the Journal, Weigle et al (3) showed that an increase in dietary protein from 15% to 30% of energy and a reduction in fat from 35% to 20%, at a constant carbohydrate intake, produces a sustained decrease in ad libitum calorie intake and results in significant weight loss….

Weigle et al’s results clearly showed that protein is more satiating than is fat, and previous studies have shown that protein is more satiating than is carbohydrate (4). Moreover, diets with a fat content fixed at 30% of calories produce more weight loss when high in protein (25% of energy) than when normal in protein (12% of energy): 9.4 compared with 5.9 kg after 6 mo; after 1 y, evidence was found to suggest that the high-protein diet, independent of the loss of total body fat, resulted in a significant loss of visceral fat (5). [1]

But there are downsides to high protein consumption. Various animal experiments have found that longevity is increased with protein restriction. Also, protein restriction promotes autophagy, which enhances immunity to intracellular bacteria and viruses. So higher protein intake may shorten lifespan and increase the risk of disease.

In a post on his blog (linked in this comment), Dennis Mangan introduced us to the “protein leverage hypothesis.” This hypothesis is put forward in a 2005 paper by SJ Simpson of Oxford University and D Raubenheimer of the University of Auckland [2].

The Satiating Power of Protein

The paper has some graphs which neatly illustrate the satiating power of protein. When animals are given a food formula with a lower protein fraction, they eat more total calories.

Here are some data from rats (b) and chickens (c). The numbers are in kiloJoules; divide by 4.18 to get calories. The animals were on feed formulas with a constant fat content, but different carb-protein ratios. Each data point represents a diet with a different P:C ratio.

If both macronutrients were equally satiating, then the animals would eat the same amount of calories regardless of their food’s protein-carb ratio. The data points would fall on a 45º line (say, for chickens, a constant 1000-kJ line connecting the 1000 kJ mark on the y-axis with the 1000 kJ mark on the x-axis).

But they don’t:  if a line were fitted to these points, it would be much closer to vertical than 45º. The rats, for instance, eat around 150 kJ protein and 75 kJ carb if given high-protein food, but 75kJ protein and 300 KJ carb if given high-carb food. That’s 225 kJ (54 calories) on a high-protein diet, but 375 kJ (90 calories) on a high-carb diet.

The chickens and rats act like protein dominates appetite control:

  • A shortage of protein makes them hungry, and it takes a lot of carbohydrate to satisfy that hunger. So they eat a calorie excess.
  • An excess of protein satisfies their hunger and causes them to quit eating while they are still in calorie deficit.

Evidence in Humans

The same sort of thing happens in humans:

Results a, b, and c are from “short-term” experiments that varied from 2 days to 6 months in length. Results d, e, f, and g are from “long-term” experiments.

People tend to gravitate toward a protein intake of 1520 kJ (360 calories). This can be construed as the “normal” human protein intake, and tends to occur near a carb+fat intake of 8000 kJ (1900 calories). So the “normal” protein fraction of the diet is 360/2260 or 16%. This is consistent with epidemiological data, which finds that nearly everyone worldwide eats near 15% protein.

A line fit to the data has the same steep slope as the animal experiments, but note something interesting. The short-term experiments have a very steep slope, but the long-term experiments have a slope much closer to 45º.

This has to happen. Otherwise, a high-protein diet would lead to permanent calorie deficit which, over time, would lead to starvation. A low-protein diet would lead to permanent calorie excess which, over time, would lead to obesity.

Since we know people neither starve nor become obese due to small adjustments in protein fraction, they must adjust their calorie intake. In the long run, protein no longer controls calorie intake. So there is great protein leverage in the short-term, but much less protein leverage in the long term.

Simpson and Raubenheimer try to develop protein leverage into a theory of obesity. It’s not a very good theory, so I’ve relegated it to an appendix.

Instead, I’d like to talk about what this satiating power of protein means for Perfect Health Dieters.

Implications for Perfect Health Dieters

We have a fairly broad healthy protein range, 200 to 600 calories per day, which brackets the “normal” protein intake of 360 calories. What happens if you shift from 360 calories protein to either the low-protein or high-protein ends of the range?

IF YOU REDUCE PROTEIN: 

At low-protein intake, your appetite goes up and total calories go up. You gain a little weight, in the form of adipose mass. This causes leptin levels to increase. As we discussed in “How Does a Cell Avoid Obesity?”, higher leptin (a) lowers appetite and (b) increases thermogenesis, or destruction of fat as waste heat.

Adipose mass increases until the actions of leptin counterbalance the influence of protein leverage.

You reach equilibrium at a slightly higher fat mass and slightly higher leptin levels than on the “normal” protein intake.

IF YOU INCREASE PROTEIN:

At high protein intake, appetite goes down and total calories decrease. You start to lose adipose mass. This causes leptin levels to go down. This (a) increases appetite and (b) decreases thermogenesis, or heat generation.

Adipose mass decreases until a new equilibrium is reached. Equilibrium is reached at a slightly lower weight and slightly lower leptin than on the “normal” protein intake.

IN SHORT:

The main effect of changing the protein content of the diet is a modest change in body composition.

  • High-protein diets make you leaner and a little lighter.
  • Low-protein diets give you a slightly higher adipose reserve and make you slightly heavier.

The effect is probably small; probably just a few pounds either way. But if you’re looking for to win a bodybuilding competition and you have to become extremely lean and “cut,” you’d do well to adopt a high-protein diet.

It’s probably not a surprise, then, that people with the leanest bodies tend to be healthy but high-protein dieters. Here’s a picture of Anthony Colpo:

I think Anthony has a healthy body, but I don’t think you need to be this lean to be healthy. He would be equally healthy with a few more pounds of adipose tissue.

Conclusion

In the book we say that higher protein intake makes it easier to add muscle, and thus that it may be favored by athletes. Based on today’s post, we can adduce two other reasons to eat a high protein diet:

  1. A more chiseled body. If you want a lean, “cut” look, like Anthony Colpo, high protein will help.
  2. A controlled appetite. In a recent post, Don Matesz stated that he liked a high-protein diet because it helped him auto-regulate his calorie intake. If your goal is “effortless” (willpower-less) calorie restriction, then high protein may help – at least for a while.

However, there are reasons to restrict protein as well. Lower protein intake is likely to extend lifespan, and can increase immunity against intracellular bacteria and viruses, which are behind many late-life diseases.

Is it possible to achieve a lean, muscular body while still gaining the longevity and immunity advantages of low protein intake? And can one lose weight comfortably without assistance from a high-protein diet?  Those will be the topics of Thursday’s post.

References

[1] Astrup A. The satiating power of protein—a key to obesity prevention? Am J Clin Nutr. 2005 Jul;82(1):1-2. http://pmid.us/16002791.

[2] Simpson SJ, Raubenheimer D. Obesity: the protein leverage hypothesis. Obes Rev. 2005 May;6(2):133-42. http://pmid.us/15836464.

Appendix: The Protein Leverage Hypothesis as a Theory of Obesity

To the satiating power of protein, the protein leverage hypothesis adds two premises:

  1. That any increase in total calorie consumption leads to weight gain which induces insulin resistance in the liver, which in turn upregulates gluconeogenesis. Contrariwise, any decrease in calorie consumption reverses insulin resistance in the liver and downregulates gluconeogenesis.
  2. That the loss of protein associated with gluconeogenesis is treated by the brain’s appetite control centers exactly the same as a decreased intake of protein, and therefore that ongoing gluconeogenesis increases appetite immensely.

The theory of obesity is that once someone starts eating a low-protein diet, their appetite goes up. So they eat a larger amount of total calories, and gain weight. The weight gain causes them to become insulin resistant in the liver. Once that occurs gluconeogenesis is no longer inhibited by insulin, and the liver converts protein to glucose willy-nilly. The loss of protein stimulates appetite. But the person has to eat a lot of excess calories to get enough protein to replace the protein lost in gluconeogenesis. So weight goes up even more. There is a vicious spiral.

If these premises were correct, then:

  • Weight would be unstable. Weight would spiral out of control upward if people ate low-protein diets, and people would wither away once they started eating high-protein diets.
  • Low-carb diets would be extremely obesogenic. Every 1 calorie reduction in carb intake below the body’s daily needs of 600 calories would induce the eating of an extra 1 calorie of protein for purposes of gluconeoegenesis, and on the order of 4 extra calories of fat (by the leverage hypothesis: the P:F ratio stays constant). So each reduction of carb intake by 1 calorie leads to an extra ~5 P+F calories and an increase in total energy intake of 4 calories. Zero-carb diets would induce ravenous appetite, consumption of an extra 3,000 calories per day above the amount needed for weight stability, and obesity and metabolic syndrome would rapidly follow.

Neither is the case.

Water Weight: Does It Change When Changing Diets? Does It Matter?

Posted by on January 14, 2011 54 comments

We’re now up to the final topic in the series reviewing experiences on the diet. Our final topic is the issue of weight gain and loss. This will take a few posts to explore. Next week will be “fat loss week.” This week, let’s look at the question of water weight.

Overweight people who come to the Perfect Health Diet from a high-carb diet seem to lose weight from the beginning. Here is a recent comment from Robert:

I started PHD a few weeks ago, after finding the blog, and then reading the book. I have only positive experiences to report…. I had been overweight in the past, and lost weight by low-calorie dieting on processed foods, along with strength training. After a while I would revert to some degree of overeating, and have to diet again. I’m mildly overweight now but I have been losing 2 lbs. per week on the PHD. Keep in mind this is before any calorie counting. I keep telling myself I will plug things in to Fitday, but so far my hunger is autoregulating itself and the weight is coming off.

However, some of our readers who came from very low-carb diets experienced immediate weight gains. One commenter on Amazon seemed to think this experience would be universal:

[I]f you are coming to the diet from a zero-carb or very-low-carb regimen, you can count on an immediate and substantial weight gain if you suddenly adopt the recommended intake of “400 carb calories [100 grams] per day of starchy tubers, rice, fruit, and berries.” (K. Hix)

Commenter Maggy reported a gain of 5 pounds in her first week:

Following your advice, I added back a bit of “safe starch” last week, and decreased protein intake, keeping sat fat and MCF pretty high. Well, I got on the scale today and have managed to put on 5 pounds! I’m trying to figure out what is going on and what I need to tweak. I do need to lose a good 20-30 lbs, and while I don’t want to compromise health, I also don’t want to put back on what I managed to lose doing a VLC diet.

Is this an adjustment period I need to get through? Maybe I’m one of those broken metabolism folks who has to stick with VLC?

Commenter Bill also experienced a quick gain of a few pounds, and wondered if it could be due to water weight:

After experimenting with adding modest amounts of “safe starches” to my much lower-carb routine, I have noticed a modest weight gain of 3-5 lbs. I wonder if it’s merely glycogen and water repletion.

Beth Mazur of WeightMaven.org agreed:

I also wouldn’t be surprised about weight gain. Presumably these folks are normally running on fairly low glycogen stores. Add some starchy carbs back, and the resulting water weight gain could be a handful of pounds presumably.

That’s an interesting question, so I thought I’d look into the matter.

Background: Glycogen, Glycoproteins, and Water Weight

Sugars are hydrophilic. If you put some water next to some sugar, the sugar will soak it up. As a result, a person’s water weight depends in part on the weight of sugars in the body. More sugars, more water, more weight.

It’s commonly stated that each gram of glycogen is associated with four grams of water; let’s take that as a general ratio for organic sugars.

A typical adult has around 500 grams of glycogen, roughly one-third in the liver and two-thirds in muscle. With associated water, this would add about 2.5 kg or 5 pounds to body weight.

But there are also several pounds of glucose in glycoproteins throughout the body:

  • Mucus in the digestive tract and airways may be as much as 80% sugar by dry weight.
  • The glycocalyx, a protective polysaccharide coat around cells, is primarily composed of sugars.
  • Hyaluronan, glucosamine, and other compounds that enable joints to move freely have much of their weight as sugar-water associations.

These sugar-containing molecules with their associated water add a lot of weight to the body. Glycogen we’ve said accounts for as much as 5 pounds; mucus probably accounts for several pounds at least; and other glycoproteins must add at least a few pounds more.

Are Glycogen and Glycoproteins Lost on a Low-Carb Diet?

It’s commonly asserted that much of these sugar-containing molecules, and their associated water, are lost on a low-carb diet. From a review of Gary Taubes’ Why We Get Fat, linked today by CarbSane:

[B]etween 5-10lbs of weight are lost on a low-carb diet due to the mobilization of the water stored with glycogen …

I argued in my “zero-carb dangers” series that a danger of zero-carb dieting was that the body would downregulate production of glycoproteins; and that reduced production of these might be quite dangerous.

For instance, reduced production of mucus in the digestive tract might increase the risk of gastrointestinal cancers, bowel diseases, and entry of infectious pathogens through the gut.

If it’s true that low-carb diets reduce water weight by 5 to 10 pounds, there must be a substantial loss of sugar-containing molecules. This is hardly likely to be healthy. Glycoproteins are essential for good health. Indeed, the evolution of glycoproteins was a prerequisite for the evolution of multicellular life!

So I would find this kind of water-weight loss quite alarming.

Let’s look for some data to see if it actually happens.

From High-Carb Diet to Fasting

In our earlier post on fasting for migraines, commenter js290 linked to a very nice post by Ned Kock, in which he talked about the components of weight loss during starvation. Ned posted this picture, taken from a textbook [1]:

Over 30 days of fasting, almost half the weight lost is from fat and almost half from water; small amounts of protein and sugar are lost.

In the first few days, water loss dominates. In the first 48 hours, 3.4 kg are lost, of which roughly 0.35 kg are glycogen, 0.1 kg protein, 0.3 kg fat, and 2.65 kg water.

So in the first two days of fasting, fully 5.8 pounds of water are lost. That’s remarkable.

Presumably, if this person had been returned to his normal diet, that weight would have been regained in a few days.

If the water loss was triggered by a loss of carbohydrate (in glycogen and glycoproteins), then a very low-carb diet might have had the same effect as the fast.

From High-Carb to Low-Carb Diets

There are some metabolic ward studies looking at what happens when people adopt low-carb diets. Here’s one that looked at an Atkins-style diet. [2]

The subjects entered the metabolic ward but continued to eat their normal diet on days 1 through 7, to provide a baseline. Then they adopted an Atkins-style diet for 2 weeks. Carbohydrate was reduced to 21 g (80 calories) per day, and they could eat as much fat and protein as they wished.

The results:

During the low-carbohydrate diet, mean body weight decreased by 2.02 kg from 114.43 kg (last day of the usual diet) to 112.41 kg (last day of the low-carbohydrate diet) …

During the low-carbohydrate diet, mean body water decreased from 46.30 kg to 45.94 kg. Body water decreased in 6 patients, increased in 3 patients, and did not change in 1 patient. After subtraction of body water, mean body weight decreased from 68.13 kg to 66.48 kg. [2]

In other words, water weight hardly changed. The weight loss was accounted for by fat loss, which was understandable because the subjects reduced their calorie intake by 946 calories per day. [2]

So in this study, water weight loss averaged only 360 g (0.8 lb), and some patients actually gained water weight on the low-carb diet!

So it looks like going from a high-carb diet to a low-carb diet needn’t lead to much loss of water weight.

From Low-Carb Diet to Fasting

I looked for some papers on what happens when a low-carb dieter starts a fast. I found this:

In her book ‘Living on Light’, Jasmuheen tries to animate people worldwide to follow her drastic nutrition rules in order to boost their quality of life. Several deaths have been reported as a fatal consequence. A doctor of chemistry who believably claimed to have been ‘living on light’ for 2 years, except for the daily intake of up to 1.5 l of fluid containing no or almost no calories was interested in a scientific study on this phenomenon.

The 54-year-old man was subjected to a rigorous 10-day isolation study with complete absence of nutrition. During the study he obtained an unlimited amount of tea and mineral water but had no caloric intake….

[The man experienced] a mean weight loss of 0.26 kg/d … [3]

If his weight loss of 260 g/day consisted of 130 g protein and 130 g fat – a plausible mix – then he was expending about 1700 calories per day. This is very plausible, and leaves little room for water weight loss.

So when a low-carb dieter starts a fast, he may lose hardly any water weight at all!

Summary and My Own Experience

These studies are inconsistent. If going from a high-carb diet to a low-carb diet doesn’t produce water weight loss, and going from a low-carb diet to fasting doesn’t, then why would going from a high-carb diet to fasting?

I confess I was surprised by the level of water loss reported by Ned’s source. I fast moderately often, and I lose typically around 1 pound during a 36 hour fast. Shou-Ching’s experience is similar. That doesn’t leave much room for water weight loss.

But clearly, some people do experience large losses of water weight when they adopt a low-carb diet or a fast, and then regain it upon carb re-feeding.

I think we have to conclude that the phenomenon of water weight loss on low-carb diets, and water weight gain on carb re-feeding, is variable across persons. In some persons it happens, and in others it doesn’t.

Conclusion

I think those sugars serve important functional purposes. Glycoproteins are essential for health. Glycogen is a desirable reserve that helps the liver manage blood glucose and muscles exert force.

Maggy asked if she was metabolically broken because she gained 5 pounds in a week by adding carbs back in. Now, a lot can happen in a week, including significant changes in fat and protein mass, and water weight changes due to changes in sodium levels. Low-carb diets tend to lead to salt loss, so that may have been a factor.

But if the weight gain was entirely due to restoration of sugar and water levels, then I’m reluctantly led to the conclusion that Maggy may indeed be “metabolically broken.” The brokenness is not in the gain of bodily sugars when she eats the carbs; it’s in the loss of these important sugars on her very low-carb diet!

If it’s unhealthy to lose those sugars, and if a metabolically healthy person can sustain the body’s sugar and water levels through a fast, then the loss of sugars on either a low-carb diet or fast suggests a damaged metabolism.

As much as Maggy wishes to lose weight, it is important to lose weight from adipose cells, not from water and glycoproteins. Her rapid ~5 lb weight gain upon shifting from a very low-carb diet to the Perfect Health Diet might have been a very good thing.

UPDATE:

CarbSane has begun a series on water weight, and has interesting numbers on water weight in adipose tissue and lean tissue, and how water weight varies between obese and lean persons. This post introduced several papers, and a follow-up contributes an interesting analysis and suggests that movement of fatty acids between adipose and lean tissue may be involved in water weight changes.

I didn’t know that extracellular water weight in tissues was so variable. Thank you CarbSane! 

References

[1] Wilmore, J.H., Costill, D.L., & Kenney, W.L. (2007). Physiology of sport and exercise. Champaign, IL: Human Kinetics. Cited by Ned Kock, “The amounts of water, carbohydrates, fat, and protein lost during a 30-day fast,” http://healthcorrelator.blogspot.com/2010/10/amounts-of-water-carbohydrates-fat-and.html.

[2] Boden G et al. Effect of a low-carbohydrate diet on appetite, blood glucose levels, and insulin resistance in obese patients with type 2 diabetes. Ann Intern Med. 2005 Mar 15;142(6):403-11. http://pmid.us/15767618. Full text: http://www.annals.org/content/142/6/403.full.pdf.

[3] Heusser P et al. Nutrition with ‘light and water’? In strict isolation for 10 days without food – a critical case study. Forsch Komplementmed. 2008 Aug;15(4):203-9. http://pmid.us/18787329.

Unfit for the Paleo Rodeo

Posted by on January 7, 2011 3 comments

Diana Hsieh of the Modern Paleo blog does yeoman’s work running the Paleo Rodeo each week, which is a fun collection of Paleo posts. (Here’s this week’s rodeo.)

It turns out that a contribution got rejected from this week’s Rodeo as spam. It was titled “Linguine with Seafood Sun-dried Tomatoes and Lemon”:

I must admit that for a time I couldn’t see anything wrong with this meal, other than that it is rather light in the meat, vegetables, and sauce. But de gustibus non est disputandum. After a half minute of puzzlement I remembered that pasta is forbidden by conventional Paleo.

Of course, the Perfect Health Diet forbids wheat noodles but happily supports rice noodles. In our house we often have rice-noodle dishes, as I mentioned recently to Kratos.

I guess it’s just as well I didn’t submit Cambridge Fried Rice to the Rodeo!

Short-Term Effects of Adding Carbs to Very Low-Carb Diets

Posted by on January 6, 2011 70 comments

In my last post, I noted that

So far, all the negative experiences [from adoption of our diet] I am aware of have come from low-carb dieters who had difficulty after adding carbs and/or cutting protein….

It’s interesting that the same dietary change – adding “safe starches” to a low-carb Paleo diet – made some people feel better and others worse.

In thinking about why adding starches can cause short-term trouble for some people, my first thought was a fascinating post from two years ago by Peter Dobromylskyj of Hyperlipid. Peter noted:

Bacterial endotoxin is a breakdown product of the cell wall of gram negative bacteria. It’s a lipopolysaccharide and even quite small amounts of it are extremely unpleasant….

Now the scary thing is that eating a high fat meal, probably based on any fat which generates chylomicrons, markedly increases your uptake of endotoxin from your gut, which is obviously full of gram negative bacteria. Eating short chain fatty acids or carbohydrate [1] does not have this effect.

Endotoxins are fat-soluble, and so fat carries them into the body. The paper Peter cited actually found an increase in blood endotoxin levels after people were fed a high-fat meal:

In humans, no significant relation was observed between cardiovascular disease risk factors, carbohydrate and protein intakes, and plasma LPS concentration. Conversely, positive correlations were observed with fat and energy intakes. [1]

The same effect was found in mice:

Compared with the control mice, mice fed a high-energy diet showed an increase in plasma LPS. However, in mice fed a high-carbohydrate diet, the increase in plasma LPS was blunted compared with mice fed a high-fat diet.

The conclusion:

Experimental data suggest that fat was more efficient in transporting bacterial LPS from the gut lumen into the bloodstream. [1]

Does this mean that one should avoid dietary fat?  No, because it turns out the body regulates the amount of endotoxin entering the body. So a high-fat diet causes the immune system to exert greater control over gut bacteria. Peter writes:

Then came a fascinating random paper [2] through my wife’s journal club meetings … It’s about superinfection with resistant bacteria when broad spectrum antibiotics are used. This is a routine problem for anyone in medicine, especially patients. The concept is very simple, you kill off the susceptible commensal bacteria in the gut and resistant pathogens have no competition, so they have a field day and superinfection causes severe problems for the unlucky patient.

Simple, straightforward and wrong.

It turns out that the immune system, that is the innate immune system (of course), continuously monitors the contents of the gut by looking at endotoxin production. Lots of bacteria mean lots of endotoxin and an active, on-guard innate immune system. Kill off 99% of your gut bacteria and exdotoxin production drops. The innate immune system goes on vacation and clostridium difficile gets in and wipes out your granny.

Simple administration of oral endotoxin to the experimental mice stopped this effect completely.

Apparently, the human body evolved to favor having a certain population of commensal gut flora. When the population is too low, immune defenses are lowered to allow gut bacteria to multiply. When the population is too high, antimicrobial peptides are released into the gut to control pathogen numbers.

Thus, during gut infections adding probiotic bacteria may help defeat pathogenic infections by causing the body to increase its immune defenses. The body is actually trying to control the numbers of probiotic bacteria, but in doing so it makes compounds that kill pathogens.

Removal of tiny numbers of probiotic bacteria can lead to a huge multiplication of pathogens:

Administration of the broad-spectrum antibiotic combination metronidazole, neomycin and vancomycin (MNV), to which vancomycin-resistant Enterococcus (VRE) is resistant, markedly increases colonization of the small intestine, caecum and colon with VRE…. It remains unclear, however, why elimination of the relatively sparse microbial flora of the small intestine increases the number of VRE by over 100–1,000-fold. [2]

It’s possible that this effect may be able to work in reverse – that addition of the small number of bacteria in a probiotic capsule can diminish the much larger population of an acute infection by 100-fold. I’ve noticed that swallowing probiotic capsules can be extremely effective against food poisoning. If you ever get diarrhea from a bad meal, take handfuls of probiotics every few minutes. You’ll be cured remarkably quickly.

The Gut of a Zero-Carb Dieter

On a zero-carb diet – especially an entirely plant-free diet like the one Charles Washington eats – lack of food will cause the population of gut bacteria to dwindle.

As in a gut depopulated of bacteria by antibiotics, this diet will cause the gut to let down its immune defenses. The body will reduce its production of antimicrobial peptides in order to help gut bacteria survive.

Perversely, this may make any pathogens that enter the body with food more likely to enter the body. It also may allow pathogens to gain a foothold in the gut. Thus, heightened infectious disease risk could be another long-term danger of zero-carb diets.

What Happens When A Zero-Carb Dieter Reintroduces Starches?

When a zero-carb dieter starts eating plant foods, suddenly gut bacteria have a lot of food, and can multiply many-fold. Bacteria can double their numbers in 20 minutes, and yeast in a few hours. That means that bacterial populations can increase 8-fold in an hour, 4000-fold in 4 hours, and ten million fold in 8 hours. Yeast can increase 4000-fold in 24 hours.

So it doesn’t take long – the very first day – before gut bacteria have multiplied by huge proportions. In the course of their fermentation, they’ll release a lot of gas, causing some bowel distress.

And along with greater numbers comes greater endotoxin release. Any dietary fats carry these endotoxins into the body. This rise in endotoxin load triggers an immune response that includes release of antimicrobial peptides, killing gut bacteria and releasing more endotoxins.

This rise in endotoxin levels and the resulting immune response may resemble a brief illness. Some known effects of a sudden rise in systemic lipopolysaccharide levels:

  • Depression [3] and depressive-like behavior [4].
  • Impaired athleticism [5]. 
  • Reduced appetite [6, 7].
  • Fever, vasoconstriction and endothelial dysfunction. [8]

Of course these effects would be only temporary. In a matter of days to a week, the immune system should re-establish an equilibrium with the gut flora and the new diet. Gas and bloating in the gut should be reduced (unless pathogens have been able to establish an enduring infection first). Endotoxin levels in the body should return to the evolutionary optimum. Higher production of antimicrobial peptides will maintain a limited gut bacterial population, even though carb intake has increased.

My Experience

My own experience is consistent with some of these expectations. When I went from zero-carb to including carbs – in my case, the change was adding fruit only, starches didn’t start for another year – my abdomen became bloated and I had gas. It was remarkable:  the very first day I ate fruit, my belly bloated up. It seemed to leave me with a lasting infection, because both the bloating and various digestive problems lasted several years. Probably the scurvy that I also had at that time was a big contributor; until I fixed the scurvy I also had gallbladder problems, and developed diverticulitis during this period, diagnosed by a barium enema.

I believe the main factor in the bloating was a colonic yeast/fungal infection that may or may not be completely gone today (it is certainly much diminished). The bloating was increased whenever I developed fungal skin infections. I suspect the yeast took over my colon while my immune defenses were depressed on the zero-carb diet and vitamin C deficiency, and multiplied immensely as soon as they had access to plant foods.

Conclusion

This hypothesis matches some but not all of the first-couple-of-days symptoms experienced by Don Matesz and his commenter SamAbroad when they cut protein and increased starches. SamAbroad became “hungry and cranky”; Don noted “decline in mood and … increase in hunger and intestinal gas and a disruption of bowel function.” In short:

  • Gas, bloating, intestinal distress.
  • Cranky mood.
  • Hunger.

The first two are consistent with a rise in endotoxin levels. The last isn’t.

However, I can imagine a few reasons why a shift from meat to starches may have made them hungry:

  • Protein is notably satiating, one reason why high-protein diets are often effective for weight loss. Mixed carb and fat, on the other hand, makes a good dessert. As we have all witnessed, many people say they are stuffed after dinner but get hungry again when they see desserts.
  • Or maybe the calories lost from the reduction in meat were not fully replaced. Plant foods have far fewer calories per pound than meat, and many people overestimate how many calories are found in plant foods. In cutting meat from

The body should adjust appetite to the diet, but this may not happen in the first few days. In short-term (3-day) trials of food mix alteration, people who increased carbs ate more food than people who increased protein. [9]

I don’t know if these explanations are correct in the specific cases of Don and SamAbroad. (Indeed, I was very surprised Don had any trouble at all, since he already eats our safe starches and I am pretty sure he also eats within our recommended optimal range of macronutrients — hat tip to commenter Beth Mazur of WeightMaven.org for a link to one of Don’s meal analyses in which he ate our recommended calorie ratio.) However, I think many people who have been on zero-carb diets can expect short-term gut distress when they first restore carbs to the diet.

In people with healthy gut flora, this should disappear in a few days. In others, like me, who have pathogenic gut populations, a gut infection may become entrenched and take longer to get rid of. Still, overall I think the inclusion of dietary carbs, and the resulting enhancement of intestinal barrier immunity, is likely to lead to long-term improvement in the body’s protection against infectious diseases that enter through the gut.

References

[1] Amar J et al. Energy intake is associated with endotoxemia in apparently healthy men. Am J Clin Nutr. 2008 May;87(5):1219-23. http://pmid.us/18469242.

[2] Brandl K et al. Vancomycin-resistant enterococci exploit antibiotic-induced innate immune deficits. Nature. 2008 Oct 9;455(7214):804-7. http://pmid.us/18724361.

[3] Weidenfeld J, Yirmiya R. Effects of bacterial endotoxin on the glucocorticoid feedback regulation of adrenocortical response to stress. Neuroimmunomodulation. 1996 Nov-Dec;3(6):352-7. http://pmid.us/9266546.

[4] Fu X et al. Central administration of lipopolysaccharide induces depressive-like behavior in vivo and activates brain indoleamine 2,3 dioxygenase in murine organotypic hippocampal slice cultures. J Neuroinflammation. 2010 Aug 2;7:43.  http://pmid.us/20678226.

[5] Sparkman NL et al. Effects of intraperitoneal lipopolysaccharide on Morris maze performance in year-old and 2-month-old female C57BL/6J mice. Behav Brain Res. 2005 Apr 15;159(1):145-51.  http://pmid.us/15795008.

[6] Stengel A et al. Lipopolysaccharide differentially decreases plasma acyl and desacyl ghrelin levels in rats: potential role of the circulating ghrelin-acylating enzyme GOAT. Peptides. 2010 Sep;31(9):1689-96.  http://pmid.us/20599577.

[7] Rorato R et al. Prostaglandin mediates endotoxaemia-induced hypophagia by activation of pro-opiomelanocortin and corticotrophin-releasing factor neurons in rats. Exp Physiol. 2009 Mar;94(3):371-9. http://pmid.us/19074588.

[8] Feng SY et al. Acute and chronic effects of endotoxin on cerebral circulation in lambs. Am J Physiol Regul Integr Comp Physiol. 2010 Mar;298(3):R760-6. http://pmid.us/20071615.

[9] Coelho JS et al. Selective carbohydrate or protein restriction: effects on subsequent food intake and cravings. Appetite. 2006 Nov;47(3):352-60. http://pmid.us/16844265.