Separating Carbs & Fats ~ My Rationale

I get a fair amount of traffic here from time to time due to my posts about Zoe Harcombe and the Harcombe Diet.  Zoe's dietary philosophy boils down to parroted Taubesian Pseudophysiology, but one of the things she advocates, that I've discussed here before, is the strategy of separating carbs and fats and having them at different meals.  She makes a lot of comments about how calories don't count and all that too ... so the Google searches on her name and/or CICO or the separating carbs & fats thing tend to land folks here at the Asylum.  As a result, apparently just enough folks know enough about my stance on carbs & fats to misrepresent my position in discussions about the web.  More than once I've been described as subscribing to "that old food combining nonsense" or things along that line.  I've long since passed the point where I could answer to these various misconceptions everywhere they are found, but in this case, it's happened enough times that I thought I'd set the record straight on this issue.

I believe that when it comes to fats and carbs, with the exception of the small amount of fat that goes to sustaining cellular structure and biological function, the two are relatively interchangeable as dietary sources of energy. Within a relatively wide range of dietary macronutrient ratios, our fuel burning ratio (the respiratory quotient, RQ) remains relatively consistent depending on activity levels. This has been born out in metabolic ward studies. So let me begin with what I don't believe. I don't believe that if you eat 25g protein with 400 more calories at a meal it matters much what the fat vs. carb breakdown of those calories is. If one eats 400 cals fat or 400 cals starch or 200 cals of each, if that's 200 cals too many, then ultimately you've stored 200 cals worth of lipid in adipose tissue at the end of the day. If anything the fat is stored more efficiently as fat and you get a few more net calories than the carbs, but it all balances out except at the very extreme ends of the spectrum. 

So, if you eat 200 cals fat and 200 cals carb together, it is true that most of the 200 cals of fat will be deposited in your fat tissue.  All the while, however, fat is constantly going into and being released from the fat tissue, so it's not like it's a "fat sentence" for you for this to occur.  Later in the day when the carbs from the meal are gone, 200 cals of fat will be mobilized and burned provided you need it.  This is why I find the arguments of Taubes and Eades and Harcombe and a whole host of others so specious -- they all focus on what's going on in the hour or two after you eat and ignore what goes on the other 16+ hours of the day.  So I don't believe in this "starving cells" thing, nor do I believe in any metabolic advantage of fat vs. carb (though carb comes out ever-so-slightly with the advantage there).  

I believe in separating carbs and fats between meals in one's diets as a STRATEGY, not some rule.  It's something I've been doing a lot more of lately as my carb intake has increased, though I have some carb or some fat at almost every meal.  Lately my macro ratios are rather Zone-like, though I almost never eat a Zone-friendly meal (a big part of Zone is meeting macro ratios each time you eat).   But enough about me.

The Rationale

1.  Food Reward/Palatability:  Whether it's FR or palatability or some less well characterized phenomenon, the combination of fat + carb is intrinsically appealing to many people and many foods people overeat fall in this category:  ice cream, chocolate bars, cakes, donuts, burgers & fries, cream mashed potatoes, bread with butter, pasta alfredo, pizza, just about every chip/snack food, etc.etc.  (sorry, don't want to needlessly tempt anyone further).    Low carbers always blame the carbs for overeating these foods when fat is every bit the devilish macro.  If you eat just boiled potatoes, you almost can't overeat.  But add butter and you'll likely eat more of the buttery potatoes.  The same goes for just about everything.  I know these are rodents, but the CAF rat study really makes the point on this rationale.  Give the rats a high fat chow or a high sugar chow and they eat about the same or a little more than if you give them a high starch chow.  But give them human junk foods and they eat more ... a lot more ... and pay the price.  They also eat more of just those foods as they shy away from the chow almost entirely.

2.  Calorie Density & Sensing:  While fatty foods have high calorie density, most are packaged with enough protein in whole foods to prevent overeating.  Common LC stalling culprits such as cheese and nuts are, interestingly enough, exceptions to this rule.  But carbs by themselves have a low calorie density ... unless you add fat.  You have to eat 50% more of a medium potato to equal the tablespoon of butter you might put on it.  If you keep fat away from your carbs, at those meals you can eat quite a lot without eating too many calories.  Our signaling seems to work well for sensing carb calories and well enough for fat calories (although see the aforementioned argument about protein) for satiety.  It doesn't seem to work well for sensing calories when these two energy sources are combined.

3.  Ancestral/Evolutionary Reasons:  If one believes at all in how we evolved -- or even adapted if evolution offends you -- one thing we can all agree upon is that ancient humans ate "real" foods, likely as "whole" as possible.  And they probably ate somewhat opportunistically.  While they likely had the brains to store non-perishable (mostly) carbs, it was for that proverbial rainy day or for when Grok was too tired to go hunt.  Grok didn't fry his wild boar in coconut fat with a side of tubers smothered in ghee.  The added fat thing is definitely not "paleo", and it is hard to imagine that Grok did any food combining.  Freshly hunted game was eaten before it spoiled, vegetation eaten as gathered or stored and drawn from when the hunt was unsuccessful.    There are really no foods found in nature where carbohydrates and fats are BOTH present at "high" levels.  Nuts, larger seeds and some legumes probably being as close as we come to that in the veggie world, assorted dairy being the only source from the animal kingdom I can think of.  I don't think postprandial metabolisms are designed for large mixed macro meals.

4.  Protein Deficiency:  If one doesn't deliberately eat protein at every meal, consumption of fat + carb foods together often leads to too low a protein consumption by percentage.  Once protein needs have been reached for satiety, too many calories have been eaten.

5.  Comfort Foods:  When one thinks of comfort foods, they are almost invariably fat + carb.  From hearty stews to ice cream.  When we eat these foods, hunger is not the only reason for eating them.  Therefore they are easy to overeat.

So there you have it.  I'm not saying that one shouldn't eat fats + carbs together, only that doing so ad libitum often leads to overeating.  So my strategy to guard against overeating ad libitum is to eat essentialy low fat or low carb at any one given time.  If I'm going to eat a high fat + carb food, which I do on occasion, I am careful to portion it out accordingly.  Never eat something from the container that you tend to find "moreish".   But I'm not claiming any metabolic magic to food combinations or that separating these macros keeps the fat I eat for breakfast from being locked away all day if I had a slice of toast with my bacon and eggs.


bentleyj74 said…
This seems reasonable, I'll be interested in follow up :)
Anonymous said…
There is a french study comparing the seperation of carb and fat on weight loss, showing no benefit - within the calorie controlled enviroment.

People have been recommending this for magic over the years, john berardi wasa major proponent, and then spread through the bodybuilding world from and the likes of Joel Marion (The cheat to lose diet) etc.

Typically they try to combine any benefit of carbohdyrate along side the woo of low carb proponents. Its highly entertaining.

You seem to be trying to build similar levels of justificiation, where the simplest is your final piece - its a strategy that enables you to prevent overeating. Done. Dusted.
CarbSane said…

I thought I stated quite clearly that it is a strategy that may help (I might go so far as to say should help most people) prevent overeating ad libitum, and I gave some reasons why I thought this was. Those reasons are not needed, I suppose, but they are nothing "magical" or controversial.

That was the point of this post b/c the impetus for this post was to distinguish my reasoning from the nonsense theories. For example, Zoe Harcombe will tell you to keep them separate b/c if you eat carbs with fat this causes the fat to get locked away in your fat cells because of inshulin. Yet she's a big fan of the insulinogenic cheese which isn't fattening b/c there's supposedly no carb-induced inshulin trapping all that fat.
bentleyj74 said…
It's also not very controversial that added fats both up the cals and the reward of any given food [unless it's already LCHF..then just cals I suppose].

I portion out high reward mixed do most people as we all pretty much know there's no such thing as "done" till the brownies are gone baby gone but the same does not apply to foods that are merely sweet or merely fatty.
LeonRover said…
Ah yes, mashed potato, green young onions, freshly crushed bulbs of garlic, lashings of BUTTER, and finally either nutmeg or cinnamon. Booo-tee-full!

Also, Sherry Trifle ( ). This was the only Christmas treat that I would steal from the fridge but one hour after end of meal. While adults were dozing, I found chilled trifle irresistable. Then back 30 minutes later. I think my mother overlooked the fact of how little remained the following day. Ambrosia fit for a Celtic God.

"I can resist everything except temptation" - Oscar Wilde


"But at a time like this, my resistance is low" - Jane Russell
Harry said…
Nice article Evelyn...thanks!

I've come to similar conclusions with respect to "either high carbs or high fat, but not both" - there's nothing magical about it, to be sure, but it is a pretty decent strategic tool to add to the arsenal.

In addition to the very good reasons you cited in its favour, this strategy also works because it maximises the two different kinds of satiety that are provoked by carbs and fats; namely 'stomach volume' satiety wrt carbs and nausea threshold satiety wrt fats (btw, these are terms I've coined, so the official terms are different no doubt).

In short, a high carb meal (especially of the whole foods variety) will tend to fill up the physical space in the stomach, and so provoke a 'full' feeling and the cessation of eating. On the other hands, a high fat meal is much lower in volume, so it does not provoke this response. Rather, it tends to provoke a slight nausea when consumed beyond a certain threshold, which gets incrementally worse as the meal continues, thus encouraging the cessation of eating.

Now, if one combines carbs and fats, the feeling of fullness does not occur until many more total calories have been consumed (because the fats have added calories without enhancing the filling up of the stomach) and the feeling of nausea does not occur (because the added carbs 'dilute' the sensing of the fats that provokes the nausea).

MM said…
"I don't believe that if you eat 25g protein with 400 more calories at a meal it matters much whether the fat vs. carb breakdown of those calories is."

What about the fact that carbohydrates have a protein sparing effect? That is, you don't have to use the protein in your diet to make glucose if you're taking in glucose (starch). Maybe it doesn't matter if you're eating lots of protein. Here's a really old study on it: The protein-sparing effect of carbohydrate

It seems that starch does make a significant difference in these pigs, but they authors also point out that the pigs are still growing.
Anonymous said…
This sounds like a smart strategy.

I find these days that when I do combine fats and carbs, I REALLY have to measure the fats and just leave it at a teaspoon of butter on a potato, or an ounce or less of cheddar in a skillet. It really is so easy to just load those carbs up with fats and have a food bomb. (And sometimes I do, for a special occasion or an allowed binge.) What is nice is after a while of limiting the fats on carbs, a little fat packs a bigger taste punch than previously.
Subcalva said…
Evelyn, it would be interesting to hear you view on the "chocolate cake" study

One hundred and ninety three clinically obese, non-diabetic adults were randomly assigned to one of two diet groups with identical caloric intake -- the men consumed 1600 calories per day and the women 1400. However, the first group was given a low carbohydrate diet including a small 300 calorie breakfast, and the second was given a 600 calorie breakfast high in protein and carbohydrates, always including a dessert item (i.e. chocolate).

Halfway through the study, participants in both groups had lost an average of 33 lbs. per person. But in the second half of the study, results differed drastically. The participants in the low-carbohydrate group regained an average of 22 lbs. per person, but participants in the group with a larger breakfast lost another 15 lbs. each. At the end of the 32 weeks, those who had consumed a 600 calorie breakfast had lost an average of 40 lbs. more per person than their peers.
Sue said…
In that chocolate cake study:

"And breakfast is the meal that most successfully regulates ghrelin, the hormone that increases hunger, explains Prof. Jakubowicz. While the level of ghrelin rises before every meal, it is suppressed most effectively at breakfast time."
Jeff Consiglio said…
There is no doubt in my mind that "carb-lipid combos" make it all-too-easy to overeat. Most of the "fattening" foods in our culture are in fact carb-lipid combos, such as Pizza, fries, Big Macs, Donuts, etc.

- How much oil would you eat if it wasn't soaked into chips or donuts?

- How much cheese would you eat if it wasn't in pizza or cheese fries?

I have been recommending to my PT clients that they be wary of carb-lipid foods for years.

I think low-carb/high-fat works well, and that low-fat/high-carb also works well if the carbs aren't sugar or refined.

But for those who think they can eat a high-carb AND high-fat diet in an ad-libitum situation without gaining weight. Good luck with that!
bentleyj74 said…
No kidding. Last night we went out for dinner and a movie...even skipping the main course in favor of a drink, appetizer, and dessert I'm sure I ate more calories than I needed for an entire day. No way I could have done that without mixed macros and HIGH reward factor. Hopefully I burned a few off cowering in my seat watching "The woman in black". Easily the best horror I've seen in years.
Galina L. said…
Thank you, Evelyn, for continuing to give me more information about nutrition bloggers.I should check that Zoe H..
Sometimes I eat something made mostly of carbs in order to keep FBS at reasonable range. Often it is a banana between meals. It doesn't make me hungry any longer afterwards as it was the case before. Looks like some metabolic healing is taking place.
CarbSane said…
Hey MM -- I was talking in the context of a "balanced diet" for the whole day, b/c I think the extreme of 80% fat vs. 80% carb would indeed shake out in favor of the carbs. It is ironic, but when one looks at the literature, it is obvious that carbohydrate deprivation favors fat deposition over lean tissue building. Folks may not get fat, but it seems VLC is a good way to make yourself skinny fat.
CarbSane said…
I'll have a look! I wonder if this is the study Dana Carpender mocked in her talk on last year's LC cruise.
At work so gotta make this quick, but I am very much liking the theory that the most important thing is to avoid hypercaloric foods and/or diets. I think we're going to learn that much of the downside of eating SAD, both upstream in the brain and downstream in the gut/liver/pancreas, are inflammation related and the best thing you can do is start eating less than you need. And the number 1 thing to do that is to avoid meals that involve lots of carbs and fats at the same time -- especially when they've been pre-combined for you in boxes or in restaurants.
SamAbroad said…
Imma play devils advocate on this one. Not total devil's advocate as the reasoning is sound, I just don't think it would play out in reality.

First of all, all the foods you mentioned are hyper-palatable in their own right. The most over-eatable thing in my life at the moment is these curry-flavoured rice crackers that are less than 1% fat, the ingredients aren't even evil, it's no MSG, just curry powder. Bowl of plain rice I will also overeat pretty easy, as in will eat some, then come back for more even when no longer hungry.

Secondly, I don't overeat homemade ice-cream made with a decent amount of honey, it's deeply rich, filling, and 'hits the spot'.

Thirdly, I have tried the low fat low carb every second meal cycling, no discernable decrease in hunger, noticeable hypoglycemia (which is absent from either low fat or low carb).

Just my 2c but as much as it sounds like a good idea, it doesn't really work as well as straight low-fat or low-carb. Weekly carb-ups can be ok, but I have to REALLY white-knuckle it to reign myself in.
Anonymous said…
If you re-read my comment, I did not say you were defining it at magical.

You final paragraph below the rationales is not what everyone takes out of it. That should have led, in the paragrah before where you are talking baout strategy. You dont mention eating less then, you mention carbs nad fat. Aligning it to the rationales of debatable quality(3), or even redundant(4)is just similar to the rationalisation that occurs within low carb (or fat) groups.

But then, "my rationale for eating this way is that it enables me to manage my caloric intake" doesnt make for a very exciting blog post
CarbSane said…
There was a news story about someone having a heart attack at the Heart Attack Grill (Google it if you've never heard of it). He was having a "Triple Bypass Burger" and they showed it on the TV with the list of what's on it, etc. 6000 cals all beef, cheese, mayo, bacon ... and one bun. I could hear the LC'ers saying how it would be healthy if only for the bun ;)

On a more serious note, I think this is why the "just eat less" plans won't work. You can't just eat less of these carb+fat foods with any regularity ... at least most of us can't.
CarbSane said…
For maintenance it works quite well and without much effort. It's funny how Frank used the word "serenity" b/c I have dubbed the summer of 2010 when I pretty much started doing this, my summer of serenity.

I'm curious about the plain rice. It may seem like you're eating a lot, but I think it would be pretty hard to overeat a low fat protein like chix breast and plain rice to excess calories.
CarbSane said…
I luuuuuv butter so I can eat a lot of it, but a little bit on veggies or a potato still does the trick.
Separating carbs and fats isn't the end-all, be-all. Folks who can easily overeat carbs (palatable or not) may have other reward-related issues and will likely need additional strategies as well.
SamAbroad said…
I would eat a bag of pre-cooked rice (400cal) and then another bag so 800cal of rice is definitely not in moderation territory!

It's just odd that I can eat ice-cream and never ever binge on it. About 350 cal is my limit.

The again I'm one of those people that can drink cream, but butter on everything and lose weight. Could some people genuinely have a crap time eating high carb? I've never really found a configuration with it that works long term. I do fine on PHD ratios and less fine on VLC so I definitely need some, but they need to be accompanied with protein and copious fat to avoid hypoglycemia.
Woodey said…
Learning a lot on your blog, thanks for the work you put in it. I like how you break things down and have a very "this is how it is" approach to health and nutrition. I wish I had come here a long time ago and saved myself some money (low carb/paleo books) and frustration from a diet that isn't all that and a bag of chips.
Andrew said…
Very well put. I've searched Google high and low looking for someone who shared my observation of high carbohydrate and high fat foods not being found in nature. Most of what I come across is the typical mainstream "knowledge". I hardly see people thinking outside of the box, and using common sense like you just did in this blog.

I've always wondered why no matter how much I eat for dinner there is always room for that pint of ice cream... Haha.
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