Ray Peat: The importance of sugar and the dangers of fat (stress) metabolism

Kay Kim

The Living Force
FOTCM Member
From experience in my life around me, I know that meat eater is more healthy and lives longer.
When I was in younger age in S. Korea, I noticed that there was not many tall person and majority population died under 60 years old.
I still remember, when person lived until 60 years old, then big celebration going on whole village but it was very rare.

Back then, the most people lived in poverty that many people might had chance to eat meat one or twice in whole year, such as New-Year and perhaps Birthday.

But nowadays most younger generation lives longer and taller than before, because they eats more meat from economic revival in country.
And I am thanks to my father for his meat eating life style in his whole life. I am still healthy and taller than most average American women.


FOTCM Member
marek760 said:
Thank you Gaby, that is really interesting, I will look for this book next time I'll be at my local library
Although that was the only health related material that I stumbled upon with so far, the book is a page turner for other reasons. Also by Weatherford:


"The Secret History of the Mongol Queens"

"Genghis Khan and the Quest for God".

The Mongol army led by Genghis Khan subjugated more lands and people in twenty-five years than the Romans did in four hundred. In nearly every country the Mongols conquered, they brought an unprecedented rise in cultural communication, expanded trade, and a blossoming of civilization. Vastly more progressive than his European or Asian counterparts, Genghis Khan abolished torture, granted universal religious freedom, and smashed feudal systems of aristocratic privilege. From the story of his rise through the tribal culture to the explosion of civilization that the Mongol Empire unleashed, this brilliant work of revisionist history is nothing less than the epic story of how the modern world was made.
Genghis Khan died when he was 65 years old after an injury during a battle. He literally fought for decades until the end. One gets an idea of the nomadic resilience and I thought the author's impressions on their diet was very appropriate. He basically sums it up in a very few words.


FOTCM Member
Laura said:
marek760 said:
Gaby said:
I stumbled upon a great example which shows how carb grains are so bad in the book "Genghis Khan and the Making of the Modern World" by Jack Weatherford. It describes in detail the time period of Genghis Khan (1162-1227) and beyond when the Mongols conquered regions of Asia and Europe. It says,

The mongols drank horses' blood and carried strips of dried meat and dried curd with him that he could chew while riding; and when he had fresh meat, but no time to cook it, he put the raw flesh under his saddle so it would soon be softened and edible.

The Chinese noted with surprise and disgust the ability of the Mongol warriors to survive on little food and water for long periods; according to one, the entire army could camp without a single puff of smoke since they needed no fires to cook.
The grain diet of the [Chinese] peasant warriors stunted their bones, rotted their teeth, and left them weak and prone to disease. In contrast, the poorest Mongol soldier ate mostly protein, thereby giving him strong teeth and bones. Unlike the Jurched [Chinese] soldiers, who were dependent on a heavy carbohydrate diet, the Mongols could more easily go a day or two without food.

Traditional armies moved in long columns of men marching the same route with their large supplies of food following them. By contrast, the Mongol army spread out over a vast area to provide sufficient pasture for the animals and to maximize hunting opportunities for the soldiers.
The book also describes the climate of the Asian territory which made the Mongols thrive relatively unharmed from infectious diseases. In contrast, when they went to a humid territory, they would get infectious diseases, making them retreat to drier and colder climates where they thrived. Thought that was interesting.
Thank you Gaby, that is really interesting, I will look for this book next time I'll be at my local library
Yes, that's the sort of thing I've come across a hundred times or more reading archaeology and history. It's just amazing that health professionals have not paid the least attention to the historical evidence. What's even crazier is that historians and archaeologists themselves don't seem to pay much attention to their own evidence!
I think some are. just attended the 18th annual "Symposium on the Paleo Approach and Functional Medicine" at UCSF here in San Francisco last weekend. From the event details:

https://www.eventbrite.com/e/ihh-ucsf-symposium-on-the-paleo-approach-and-functional-medicine-tickets-28506409438# said:
Join us for an inspiring and informative day with the global leaders in functional medicine and Paleo! You will hear cutting-edge evidence-based perspectives on functional medicine and nutrition from the top experts in the world. Our 18th annual conference will be live streamed in HD and include Q&A through Twitter (your ticket will give you lifetime access to view the videos after the event).

Learn countless tips, strategies and secrets to eating Paleo, and the latest research from functional medicine about how to eat, move and supplement for improved health. You will understand the power of the keto diet for weight loss and brain health, hear Chris Kresser's new paradigm for adrenal fatigue, see how our conventional wisdom about insulin is being overturned, and much more.

All tickets (both in-person and livestream) are entered into a raffle to win free prizes donated by our speakers! We will have a delicious Paleo lunch catered by an award-winning group (details below).

Chris Kresser, LAc, internationally recognized functional medicine practitioner, blogger, and New York Times best-selling author of The Paleo Cure

Robb Wolf, research biochemist and New York Times-best-selling author of The Paleo Solution

Michelle Tam, PharmD, world-renowned food blogger and New York Times best-selling author of Nom Nom Paleo

Shilpa Saxena, MD, Institute for Functional Medicine (IFM) Faculty, Faculty of Integrative and Metabolic Medicine at George Washington University and the creator of Group Visit Toolkits

James Maskell, founder of The Evolution of Medicine and The Functional Forum

Stephan Guyenet, PhD, neurobiologist, obesity researcher, and well-known ancestral health blogger from Seattle

Akil Palanisamy, MD, Harvard-trained integrative medicine physician with expertise in functional medicine and Ayurveda, and author of The Paleovedic Diet

Nicolette Hahn Niman, JD, livestock rancher, environmental attorney and author of Defending Beef: The Case for Sustainable Meat Production

Ron Sinha, MD, internal medicine physician with expertise in corporate wellness and culturally tailored health programs, and author of The South Asian Health Solution
The highlight for me was probably Robb Wolf. He is an engaging speaker and he presented on the use of a ketogenic diet to treat traumatic brain injury. Stephan Guyenet was also interesting, he spent an hour debunking the theory that a high carb diet -> high insulin -> obesity. He didn't spend much time discussing what he thinks actually causes obesity, but I gathered that he considers it a complex condition (genetics, lifestyle AND diet) and that the total amount of calories consumed is more important than the carbs/fat/protein ratios. He discussed many studies, but I'm not sure I'm convinced....

Several of the presenters (Chris Kresser, Shilpa Saxena) discussed aspects of the functional medicine approach. For those who aren't familiar with functional medicine it is a paradigm that attempts to diagnose and treat patients in a holistic way by looking at their chief complaint as a single symptom in a unique constellation and designs treatments that focus on diet and lifestyle.

I found it pretty encouraging that there were so many UCSF med students along with nutritionists, acupuncturists and other medical professionals interested in the "ancestral health movement", there were hundreds of people attending the conference.

The even organizers are supposed to send us a link so we can view videos of the presentations so if anyone is interested I can look into sharing them. I'm not sure what their policies are so I would have to check. I can also elaborate on specific presentations.


FOTCM Member
New study that says, basically, the amount of fat you eat is irrelevant to the type and health of gut biota, but eating sugar changes the gut microbiota, induces gut inflammation and alters vagal gut-brain communication, associated with increased body fat accumulation. Attached as pdf.


Hello H2O

The Living Force
FOTCM Member
Laura said:
New study that says, basically, the amount of fat you eat is irrelevant to the type and health of gut biota, but eating sugar changes the gut microbiota, induces gut inflammation and alters vagal gut-brain communication, associated with increased body fat accumulation. Attached as pdf.
Interesting study. But I kept looking for the HF/LSD (High Fat/Low Sugar) results in the study but could not find them.

Then I saw this: "The combination of HF and HS exacerbated the obese phenotype,
however, because we did not include an HF/LSD group, we do not know if these effects are
additive or synergistic."

This seems to be a big omission, and I am wondering why they did that.


FOTCM Member
Laura said:
New study that says, basically, the amount of fat you eat is irrelevant to the type and health of gut biota, but eating sugar changes the gut microbiota, induces gut inflammation and alters vagal gut-brain communication, associated with increased body fat accumulation. Attached as pdf.
I forgot about this one. The interesting thing about this study is that in the methodology the diets containing sugar were "LF/HSD and HF/HSD primarily containing refined carbohydrates and were matched for sucrose content;"

Throughout the paper the authors state that the main problem with the HF/HS diet and the LF/HS diet were caused by endotoxin. So bacterial lipopollysaccharide seems to be the real issue. The fact that they didn't test a HF/LS diet is strange, but I think that the quantity of endotoxin in the blood and negative consequences may have been similar to high sugar.

Endotoxin is transported into the blood stream on both high fat diets and high sugar diets. From what I understand this is not necessarily a bad thing, as long as the system has the necessary protective substances to inactivate the endotoxin. High sugar diets cause rats to become obese, but when taken with glycine - the problems are completely reversed. This suggests that sugar is not necessarily the problem, but the bacterial metabolism and subsequent endotoxin are the real culprits.

Read this well-referenced article below about it:
It’s about five years since I started actively reading health literature. During these years, I’ve read dozens of health books, thousands of scientific articles and I’ve followed more than 200 different health blogs to gather as many good ideas as possible.

There have been many interesting approaches to optimal health, but it has always been difficult to understand which opinion is the “right” one. Some of the common questions include:

– Should we avoid saturated fats, or polyunsaturated fats, or omega-6, or omega-3 fats? (William Lands vs. Chris Masterjohn vs. Ray Peat vs. Brian Peskin vs. Dariush Mozaffarian vs. Caldwell Esselstyn)

– Is sugar healthy or bad? Can starch be healthy? (Ray Peat vs. low carb community vs. Paul Jaminet)

– Is animal protein a good or bad thing (T. Colin Campbell & Vegan community vs. Denise Minger & Loren Cordain & Paleo community)

At first it felt like it was very difficult to trust anybody’s point of view on these issues, because there always seemed to be some contradictory evidence or “paradoxes.”

However, at some point, I started focusing mostly on the possible mechanisms of chronic disease in general and finally found some powerful ideas that seemed to explain some of these important questions, and the paradoxes as well.

Metabolic Rate, Health and Red Light
One of my first important findings was the Broda Barnes’ idea that insufficient thyroid function is a very important cause of many kinds of ailments such as heart disease, depression, fibromyalgia, migraine, menstrual problems, and skin diseases. Many 180DegreeHealth ideas have been heavily influenced by Barnes’ work.

In 1976, Barnes wrote that 40% of the U.S. population suffered from low metabolic rate, but he didn’t really speculate about the possible mechanisms causing this problem. However, I noticed that biologist Ray Peat had been thinking of these issues for decades.

In some of his articles, Peat pointed out that red light has important metabolic effects, and when I started investigating the issue, I found out that red light and near-infrared light have been beneficially used for almost all kinds of diseases – and they have very important pro-metabolic effects. In some cases, it seems that near-infrared light in the form of a “low level laser therapy” could even cure chronic diseases such as clinical hypothyroidism.[1]

The biological effects of red light seemed to explain at least a part of the “low metabolism” epidemic, but there were also alternative explanations I wanted to investigate.

Diet, Endotoxin and Inflammation

Many studies showed that “endotoxin” and inflammation could cause disturbations of thyroid hormone metabolism. When I looked more closely at the research, many of the dietary “paradoxes” finally started to make a lot of sense.

When you eat an unbalanced diet high in fat/sugar/alcohol, you get bacterial stuff called “endotoxin” into your bloodstream.

Endotoxin is not very harmful in itself, but it can activate your immune system via a toll-like receptor 4 (TLR4) which is a very important factor behind metabolic syndrome and other chronic diseases.

Many animal studies have shown that inappropriate amounts of junk food increase endotoxin and lead to abdominal obesity and other problems such as high blood pressure and impaired thyroid hormone metabolism. Studies have also shown that you get the same health problems from a sole endotoxin injection, without the junk food.

It seems that the fat/sugar/alcohol we are eating is actually not so harmful. The harm doesn’t come from these macronutrients. It comes from the diet-induced increase in the blood levels of endotoxin and the subsequent immune reaction. There are actually many studies showing that if you reduce endotoxin levels or reduce inflammation, you make rats very resistant to diet-induced obesity and other problems.[2-15]

More on this subject has been written on-site HERE by Andrew Kim.

Glycine: The “Miracle Nutrient”

At some point, I found some interesting research articles about glycine which is a “non-essential” amino acid.

There were papers showing that dietary glycine gives a strong protection from endotoxin, and also protects the liver from many kinds of poisons.
But when I looked further, I also found more than two hundred glycine articles showing that this nutrient also protected animals from diabetes, cancer, methionine, ischemia, hemorrhagic shock, hypercholesterolemia, lead and cadmium toxicity, dental caries, gastric ulcers, birth defects, and several other harmful things. In one study, it also significantly increased the lifespan of rats.

But those effects weren’t even the most interesting ones. I got very excited when I saw the astonishing findings of one Mexican research group.
This research group did something quite nasty to their rats. They added 30% sucrose to their water for 20 weeks. Consequently, the rats got a huge amount of calories from their drinking water and thus their food intake decreased by more than fifty percent. That equals a huge decrease in protein, mineral, and vitamin intake as well.

The rats developed full-blown metabolic syndrome in 20 weeks. But then after 20 weeks the researchers also added 1% glycine to the drinking water. In 4 weeks, the sugar-fed rats became almost as healthy as the control group. With glycine, the rats’ blood pressure, fat cells, blood markers and many other things quickly became normalized despite the continued sugar feeding and low nutrient intake.[16]

This result wouldn’t sound even believable to me, if there weren’t a couple of other reports showing similar effects. For example, one study showed that a high-glycine protein source (scallop) prevented the harmful effects of a high-fat, high-sugar diet while other protein sources led to a very significant weight gain:

“In conclusion, intake of scallop muscle as the sole dietary protein source completely prevented high-fat, high-sucrose-induced body mass gain and fat accretion without affecting lean body mass. Furthermore, scallop feeding improved plasma lipid profile in C57BL/6J mice compared to mice fed diets with protein from chicken, cod, or crab. Correlation analyses revealed strong, highly significant inverse correlations between intake of taurine and glycine and body fat mass, as well as strong, highly significant correlations between glycine and especially taurine intake and improved plasma lipid profiles.”[17-20]

These protective effects of glycine seem to be related to the fact that glycine decreases inflammation by hyperpolarizing immune cells via “glycine-gated chloride channels,” preventing an exaggerated, harmful immune response to endotoxin and other stimuli. I have written about this in my own blog.

5. An anti-inflammatory diet

I mostly agree with Matt’s ideas about a healthy diet (outlined in his books such as Diet Recovery 2 or Eat for Heat), but I would personally emphasize the importance of nutrients that protect us from endotoxin and the subsequent immune reaction.

While glycine seems to be the most promising anti-inflammatory nutrient, other nutrients such as antioxidants, fiber, probiotics, carnosine, short-chain fatty acids, zinc and vitamin K1/K2 have been shown to have some similar protective effects. Histidine seems to be an especially healthy nutrient according to a recent double-blind supplementation trial with very impressive results.[21-47]

I suspect that saturated fat is the healthiest type of fat, but I also think that it’s healthy only in the context of an anti-inflammatory diet that includes antioxidants, fiber, or glycine. Without the antioxidants, fiber, or glycine, saturated fat might increase endotoxin and inflammation, and cause health problems.[23,48]

And similarly, the effects of sugar also appear to be very context-dependent. The research I’ve seen suggests that sugar is safe when the diet is high in antioxidants or glycine. Honey is healthier than the sugars it contains.[49]

When we are thinking about the health effects of a single nutrient, I think the context matters a lot.

And this logic applies not only to fat and sugar, but also to protein. Denise Minger has explained that animal protein or methionine can be harmful but mostly on a glycine-deficient diet.

As Ray Peat said, “Context is everything.”

In this article, I’m mostly just scratching the surface of the topic of chronic diseases and metabolic syndrome.

What I’m trying to say, is that most health problems seem to be largely associated with inflammation and low thyroid function. These are the health markers that we should possibly prioritize over others.

When we try to prevent heart disease, we most often focus on only cholesterol levels, ignoring that thyroid function might be much more important. Same with fibromyalgia, in which the focus should probably be on energy metabolism.

When we try to prevent diabetes, obesity or liver cirrhosis, we most often focus on blood sugar regulation or sugar/fat intake, ignoring the role of endotoxin and inflammatory processes, which are the main factors behind those diseases.

Some food for thought.
Link here


FOTCM Member
Keyhole said:
So, here is just a brief overview of the dietary experiment I have recently been undertaking:
2-3 cups coffee per day with 1-2 tablespoons of unrefined organic sugar - No longer jittery feelings nor stress response to coffee. (...)
I'd like to comment on the above section of Keyhole's post. I've been trying to give up coffee multiple times but I suspect I have a really hardcore addiction to it. I guess I'd need a longer holiday to achieve this as quitting coffee cold turkey makes it hard for me to function well - especially at work. My longest break from coffee was two weeks - and fatigue caused by stopping coffee didn't diminish at all during that time.

I used to drink black coffee without any sugar in it. Reading Keyhole's posts about stress response made me wonder because I never experienced any "jittery feelings", or any other sensations that could fit the description of stress response.

However, adding a spoon of honey to my first coffee of the day has had a very positive result: I don't need more than 2-3 cups of weak coffee per day anymore. That's down from 7-8 I used to drink! Also, I don't experience caffeine crushes during the day anymore and I often catch myself making a cup of coffee because it's time for coffee - not because I need to wake up.

It's been a couple of months since I added honey to my morning cuppa and having recently read Gabor Mate's book "When the Body Says No" I began to wonder about the impact of hidden stress that is not consciously noticed. This may be a very far shot, yet I do wonder if there is a link in my case.

Keyhole said:
B2, B3, B6, Vitamin A + E, glycine (2 tablespoons throughout the day), bone broth (1 large mug per day).
Strangely enough, although glycine significantly reduces my sugar cravings, it also makes me super sleepy so I have to take it late in the day.


FOTCM Member
Read this morning:


Does Carb Cycling Work? It Depends.
By Mark Sisson

Keto may not be for everyone, and low-carb is not the only way to eat well, but most would agree that people in the modern world tend to eat way too many carbohydrates—far more than their lifestyles and activity levels warrant. Along with some other big factors, excessive intake of refined carbohydrates is a major player in the modern epidemics of obesity, diabetes, heart disease, and other disorders. This is no longer controversial. Reducing carbs is a good move for most folks.

The majority of my readers are on some kind of low carb diet. Maybe they’re not fully keto. But they all tend to acknowledge the utility of limiting one’s carbs to only those they need. One of the more common questions I receive from this group concerns carb cycling—periodically adding more carbs to an otherwise low-carb diet.

Should it be done? If so, do certain contexts make carb cycling work better or worse?

Let’s have a discussion.

The main reason people here want to introduce additional carbs to their regularly scheduled keto or low carb diets is for the supposed performance benefits. Fat and ketones are great for slower, less intense movements like hiking, jogging, and other endurance activities, the story goes, but you really need glycogen to power intense, anaerobically-demanding pursuits like CrossFit and sprints and powerlifting. Since carbs are the easiest way to replenish muscle glycogen, low-carbers who care about their physical performance need to eat carbs. That’s the conventional wisdom, at least.

Enter the cyclical ketogenic diet, a regimen that promises to let you have your cake (of varying macronutrient ratios depending on whether it’s refeed day) and eat it too. Reap the benefits of keto—improved fat-burning capacity, increased endurance, boundless energy, caloric efficiency, clear-headed cognition—and of carbohydrates—increased power output, fully-stocked glycogen reserves—with none of the downsides.

Does it work?

Formal research is quite limited at the moment. What we have suggests that certain forms of cyclical ketogenic dieting are unnecessary at best and counterproductive at worst.

One recent study actually tested this, pitting ketogenic dieters against cyclical ketogenic dieters for fat loss and exercise performance. The keto dieters stuck to a typical keto diet for the 8 weeks—75% fat, 20% protein, 5% carbs. The cyclical keto dieters were keto 5 days a week and spent 2 days refeeding on carbs. Throughout the study, both groups lifted weights 3 times a week and did high intensity interval training (HIIT) twice a week. When the 8 weeks were up, they ran some body composition and performance tests.

What happened?

There were no differences in performance. All those carbs—16 days of carb refeeds—weren’t enough to help the cyclical keto dieters perform any better in the gym than the keto dieters. And this was strength training and HIIT, which are supposed to require carbs for optimal performance.

There were differences in body composition. The keto group lost more body fat and didn’t lose any lean mass. The cyclical keto group lost less body fat and significant amounts of lean mass. You can’t get any more stark than that: Keto was way better for body composition.

My takeaways?

I see a lot wrong with the 2-day refeed approach. For one, these subjects were trying to adapt to keto. They weren’t experienced. Right off the bat, that’s a lot of time to be gorging on carbs while ostensibly trying to become keto-adapted. Hard to make good adaptations when you’re doing 2 days of high carb every week. One step forward, two steps back.

I imagine “targeted keto”—eating small boluses of carbs before/after training—would work better than 2 day refeeds. Hopefully, research into that type of carb cycling is coming.

These guys were training pretty hard, and pretty Primally: 3x a week lifting, 2x a week HIIT. It seems like basic strength training isn’t glycogen-dependent enough to warrant 2 day carb feeds. Seems HIIT isn’t either, though I didn’t catch the exact protocol.

They also did a followup with the same groups where they reintroduced carbs in two ways. One group slowly introduced carbs, little by little, eating 1 grams per kilogram of bodyweight per day. The other group just went whole hog, eating 3 grams of carbs per kilogram of bodyweight each day. The former group gained little to no fat, and was even able to put on lean mass. The whole hog group gained more fat and failed to gain lean mass. To me, this supports the notion of small targeted doses of carbs when refeeding, rather than massive binges.

Other studies find that for strength training—basic moderate volume lifting—keto is great. You need some initial glycogen to help with the lifts, but you don’t need to constantly refill it. Besides, and many people forget this, you still have glycogen on keto. You still refill it on keto, just more slowly. Doing something like CrossFit four days a week probably works better with some carbs because it’s so glycogen-dependent and you’ll need quicker repletion. Yet, even CrossFit WODs are doable on keto, provided you give your body enough time in between sessions to recover.

What about gains? Don’t we need carbs to build muscle? Studies show that the insulinogenic effect of protein alone is adequate for post-workout muscle protein synthesis. Adding carbs doesn’t augment the effect. And research on full-blown ketogenic trainees shows they can effectively gain muscle.

Another reason people wonder about carb-cycling is to overcome fat loss plateaus. There’s some truth to this, as I discussed several years ago in a post on carb refeeds and weight loss.

Spending too long a time in a low-carb, calorie-reduced state can reduce leptin, a hormone that regulates energy expenditure. Low leptin, low energy expenditure, higher appetite, harder weight loss.

A short carb refeed can boost flagging leptin levels enough to spur additional fat loss.

But as the previous study shows, carb refeeds won’t improve your body composition (they’ll actually worsen it) unless you’re already fat-adapted. I’d go one further and say carb refeeds won’t help you lose fat unless you’re fairly lean. They’re better for the person battling those last few stubborn pounds than they are for the obese person just beginning their weight loss journey.
If you still want to carb cycle, heed these suggestions:

Make sure you need the carbs. You should be doing serious glycolytic work that depletes muscle glycogen on a regular and frequent basis. Think CrossFit. Think jiu-jitsu. Think hill sprints for 30 minutes. Lifting and doing sprints might not be enough to require extra carbs.

Do targeted refeeds, rather than free-for-all benders. Consider 20-30 grams of carbs with your workout, not 2 days of bear claws and pizzas. Besides, you can always add more if the initial dose wasn’t enough.

Get adapted first. Don’t get ahead of yourself and shortchange your results. The most scientifically-validated complex carb refeeding scheme won’t do anything if you’ve only been keto for three days. Wait six weeks (at least) to adapt, and then try.

Don’t refeed because you miss French fries. Refeed because you have actual reasons.

Don’t refeed because you’re going through the keto flu and want to alleviate the discomfort. Read my post on the keto flu and push through.

If you’re refeeding to lose body fat, make sure you’re truly on a plateau. “Being on a plateau” assumes you’ve lost significant amounts of weight and are now stuck. It doesn’t refer to those just getting started.

Few people truly need to carb cycle. It can be helpful for certain situations, provided you satisfy the criteria outlined above, but don’t think it’s a requirement for healthy dieting.

It’s nice to have options, though. Hopefully after today’s post you know what your options actually are.


FOTCM Member
Yeah I read about something like this from Mark yesterday. Thanks for posting it up Laura.

Interestingly enough, I was thinking to post the article below yesterday but didn't get round to it. It talks about how fat and carbohydrate diets are equally effective in weight loss. I agree with Mark that if someone is ketogenic, they should stick to it. If it doesn't work, they need to examine their lifestyle etc, and possibly reconsider switching fuels to carbs and less fat. The mixture seems to skew the system.

It seems that weight loss is very little to do with the fuel source, but very much dependent on caloric intake and energy expenditure. I am tending toward thinking that macro-nutrients are of little importance when compared with macronutrient quantity , physical activity, and ability to effectively burn those calories. For some people they are better at burning fat, other people are better at burning carbohydrate.

The problem with the western diet is high fat and high carbohydrate foods in one piece. The idea of "craving sugary foods" is completely misinterpreted - we do not crave refined sugar, we do not crave hard-boiled candy sweets. We crave chocolate, donuts, potato chips, and cakes. These foods are not simply high sugar foods, but are extremely high fat aswell and ultimately calorie-dense. The overconsumption of the two fuels at once leads to massive over-caloric consumption.

Check out this article by Stephan Guyenet:

Meta-analysis: Impact of carbohydrate vs. fat calories on energy expenditure and body fatness

Posted on March 20, 2017 by Stephan Guyenet

Sometimes, a meta-analysis (quantitative study of studies) is just what the doctor ordered to inoculate us against the shortcomings of our own cognition. When a topic has been studied extensively and it has produced many studies of varying quality, this lends itself to incorrect conclusions because we can find studies to support almost any belief. This is problematic because we naturally tend to gravitate toward evidence that reinforces pre-existing beliefs, and away from evidence that challenges beliefs. Called confirmation bias, this phenomenon afflicts all of us and has to be actively managed if we want to arrive at reliable knowledge. Systematically examining a body of evidence and integrating it mathematically is a useful tool for combating this bias. A new meta-analysis examines the effect of carbohydrate vs. fat calories on energy expenditure and body fatness, giving us the most objective view of this question to date.

The study

Recently, Drs. Kevin Hall and Juen Guo published what I believe is the first meta-analysis of controlled feeding studies that compared diets of equal calorie content but differing in carbohydrate and fat content (1). They only considered studies in which all food was provided by researchers and protein intake was held constant between diets. Their outcomes were energy expenditure and body fatness.

The results

They identified 28 studies that met their criteria for energy expenditure. Combining the data of these 28 studies, they found that calorie-matched diets predominating in fat vs. carbohydrate have almost identical effects, but higher-carbohydrate diets do lead to a slightly higher energy expenditure. This difference was statistically significant but of little medical or practical relevance, since it only amounted to 26 Calories per day. This slightly higher energy expenditure is consistent with the fact that the metabolism of carbohydrate is slightly less efficient than the metabolism of fat, meaning that a bit more energy is wasted*.

Examining the data, the paper’s result is not hard to believe because only 8 of the 28 studies reported that lower-carbohydrate diets led to a higher energy expenditure than higher-carbohydrate diets, and among those 8, the results were only statistically significant in four. In contrast, 20 studies reported higher energy expenditure with higher-carbohydrate diets, and that was statistically significant in 14. One can choose individual studies that support either belief, but the overall evidence suggests that the relative carbohydrate and fat content of the diet has little impact on energy expenditure.

Onward to body fatness. Hall and Guo identified 20 controlled feeding studies that reported changes in body fatness on equal-calorie diets differing in fat and carbohydrate content. Echoing the energy expenditure finding, they found that diets predominating in carbohydrate or fat have similar effects on body fatness. Yet higher-carbohydrate diets do lead to a slightly greater loss of body fat per calorie, amounting to a 16 gram per day difference. This is actually a larger difference than one would predict from the difference in energy expenditure, which would only be 2.8 g/day.


Given this new meta-analysis, I think it’s now fairly safe to say that in a general sense, equal calories from fat and carbohydrate have similar effects on energy expenditure and body fatness, with a possible small “metabolic advantage” for higher-carbohydrate diets. This doesn’t imply very much about the real-world effectiveness of low-fat and low-carbohydrate diets because it doesn’t factor in free-living calorie intake, but it is relevant to certain popular theories about how those diets work. The upshot is that you shouldn’t expect altering the carbohydrate-to-fat ratio of your diet to work magic on your metabolic rate, but rather you should choose a diet that controls your calorie intake effectively and sustainably.

It is no longer tenable to suggest that carbohydrate per se reduces energy expenditure and causes the accumulation of body fat independent of calorie intake. This idea was never very well rooted in evidence, but now that we have a meta-analysis it is clear that it resulted from confirmation bias.

This meta-analysis leaves many questions unanswered. Is the same effect observed during weight gain, weight maintenance, weight loss, and weight loss maintenance, or could the ratio of carbohydrate to fat matter in these scenarios**? Is the effect observed equally at moderate macronutrient ratios and at the extremes? We have individual studies that address these questions, but no meta-analysis yet.

Hall and Guo’s paper is not just a meta-analysis. It’s a review of obesity energetics, body weight regulation, and their relationship to diet composition. It is hands-down the single most informative paper I’ve encountered for explaining the relationship of energy intake and expenditure to body fatness, and the big-picture view of how the body’s energy control systems work. It comes from a research group that is at the leading edge of these questions. It took me years of study to formulate the high-level perspective that you can now get from an hour of reading (1). It also dovetails nicely with chapters 1, 6, and 7 of The Hungry Brain.



The Living Force
Keyhole said:
The problem with the western diet is high fat and high carbohydrate foods in one piece. The idea of "craving sugary foods" is completely misinterpreted - we do not crave refined sugar, we do not crave hard-boiled candy sweets. We crave chocolate, donuts, potato chips, and cakes. These foods are not simply high sugar foods, but are extremely high fat as well and ultimately calorie-dense. The overconsumption of the two fuels at once leads to massive over-caloric consumption.
I think the problem is still sugar, or simple carbohydrates. Would anyone bother eating these foods if they didn't contain sugar? Probably not. It's the hook that gets people to eat them. But, then I'm a sugar addict.

I'm wondering what part gut bacteria plays in the type of diet people eat. I personally don't think people can 'cure' obesity or 'switch off' the cravings by will power and psychological attention alone. It might be a catch 22 situation involving their genetics, their gut bacteria, as well as their psychology and emotional state. These factors may well be at the root of all disease. Addressing one will not necessarily resolve any issue, as it does not address any of the others.
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