The Dietary Strategy of Separating Carbs & Fats

The recent post on the Harcombe Diet reminded me of some things that I've posted here regarding the separating carbs and fats in one's diet.  Almost a year ago now, I wrote this post:  Separating Fats & Carbs

In that post I laid out my rationale for this dietary strategy to prevent obesity.  It is also a strategy I generally employ to this day for maintaining my losses thus far.  Personally, I doubt this is a viable ad libitum strategy for weight loss that I'll discuss later.  

But the rationale for this approach is pretty simple.  First, mammalian infant food (aka milk) aside, I cannot think of any whole food in nature that is high in both fats and carbohydrate simultaneously.  The closest other foods would be some nuts and legumes that are relatively high in one while containing significant amounts of the other.  The human metabolism is not really built well to handle large mixed intakes of these two fuel sources, and yet our digestion and normal metabolism is pretty efficient at absorbing and sequestering them at the same time.  It seems more that the body is "wired" to sense nutrients, not calories.  Thus carbs, proteins elicit insulin (and other) hormonal responses designed to effect transport of these nutrients to the appropriate target tissues while fat elicits other responses (e.g. incretins and chylo-stimulated ASP) designed to effect the storage of fat in the lipid buffer.  These hormones seem to be involved in signaling satiety, but if we learn anything from those CAF-eteria rats, it's that the satiety signals don't match the caloric intake when the foods are calorie-dense, generally highly palatable CF foods.   So, for example, perhaps 30g protein sends up the satiety flag.  If it's accompanied by 50g carb that's a little over 300 cal.  Add in just 1T fat and your up over 400 cal just like that.  We're not wired to sense that 1T fat.  Same goes for the same 30g protein accompanied by 22g fat totaling just over 300 cal.  Add a little less than just 1/2 cup rice and you're again up over 400 cal.   Neither the 1T fat nor the 1/2 c. rice is a lot of food.  Can you say passive overeating??

This nutrient sensing theory is born out in LC studies that measure intake before and after removing most carbs.  The subjects do not increase protein and fat intake, actually they generally hold steady or even reduce slightly too.  Low carbers will tell you that this is proof that it's the carbs that are fattening that are causing us to eat so much.  But as that one study I reference frequently replacing 15% fat with protein, resulting in a LF diet, produced much the same result as does eating a low fat diet.  Folks don't tend to eat more carbs in absolute terms.  Where all of this went awry that is usually blamed on the LF diet itself is the phenom of Snackwells (and do those FiberOne commercials sound awfully familiar??) and other processed crap being "OK" b/c they were low fat.    We see it all the time now in LC circles where folks eat LC cheesecakes and brownies and wonder over the stalls if it's all about just the carbs.

My rationale for separating carbs and fats has nothing to do with this notion that insulin elicited by carbs will trap/accumulate the fat consumed with it.  Our energy balance over the course of 24 hours or several days is what ultimately determines if we accumulate excesses or draw on reserves and lose fat mass.  I'm of course ignoring very targeted and "extreme" strategies employed by various athletes/body builders to enhance performance and/or build muscle except to say that unless you are one of these, it's probably better to ignore much of that research as it will likely make not a wit of difference for you.  For the vast swathes of the rest of us folks, it really boils down to CICO.   Obviously many humans are able to balance  CI to CO needs without any conscious effort.  But in our modern obesogenic environment, I know very few who are able to actually do that.  Usually some conscious effort is required to maintain a normal weight, and as someone recently commented here, for someone to achieve a body that would be considered "model" by various standards, this effort is not only conscious but considerable.  

So in addition to choosing whole foods, one way to expend the least conscious effort to control intake to maintain a reasonable bodyweight would be to separate those carbs and fats between meals.  Eating rice or potatoes?  Go easy on the butter and cream and have with lean protein.  Eating fatty cut of prime rib?  Pass on the starchy sides (or go really easy!), and I might add don't put butter or a fatty sauce on a fatty meat!  Have a hankering for Doritos?  Buy a snack pack or count out a serving size from that jumbo bag and put the rest away.  It is very difficult to overeat plain carbs just as it is difficult to overeat whole fatty foods.  Eating at McD's, get the smaller sandwich and/or fries and make note to go lighter the rest of the day.  If you really must eat one of those meals that would qualify for a test meal in those studies (e.g. say 200g carb + 100g fat), consider fasting the rest of the day and into the next ;-)

To lose weight with such a method?  I contend most overweight/obese have a broken "stop signal" and to produce the necessary calorie deficit, this approach may not, make that probably will not, be sufficient or may only get you so far down the scale before the dreaded plateau.  Some good old fashioned weighing, measuring and counting might just be in order at this point.

In the post from a year ago, I did go into some thoughts on separating these macros on a longer scale.  For example alternating days and such.  I do believe this too can be an effective strategy.  This can muster the power of "inefficiency" switching fuel burning up and keeping the body guessing which enzymes it needs today.  Or it may just work as a sustainability trick.  I'm not sure about some of the longer cycles employed by some.  But one thing I'm very sure of:  If you are one of those people doing a very high fat version of  VLC for days on end who is unable to sustain that w/o going on a carb bender.  STOP.  This is far worse for you than even eating the SAD.  And I'll even go out on a limb here and say that's not just my opinion, but fact.  If I had the time I could swamp this blog for days with peer-review studies backing up all the reasons why you shouldn't do this!  One last caveat would be that if your cycles result in longer periods of alternating calorie deficit and surplus, you may also be sabotaging your metabolism.  Day to day fluctuations are normal, even a couple of days.  But it is not controversial that caloric restriction (intentional or not) lowers resting metabolic rate and may also cause the metabolic cost of activity to go down (e.g. the body becomes more efficient in performing the same work).  Such adaptation may last well into the "binge" or period of energy surplus so that calories will not average out over the long term in the same way as they would day to day.

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So one of the things I've seen people  write about me when they are directed to this blog is "oh she's one of those food combiners" or "she's spouting that tired separate carbs and fats canard".  I wanted to clarify that I'm not.  Or at least not providing some metabolically advantageous rationale for doing so that will produce "effortless" weight loss because calories don't matter.