Should we worry so much about preserving "Lean Mass" in people who got obese on the SAD?

A few years ago now, researchers led by George Bray of Pennington did a classic overfeeding study, to interesting result.  I blogged on that study in some depth here, but I'll include a brief summary now:
  • Metabolic ward study
  • Determined weight maintaining caloric intake over a period of 13-25 days on a standard diet P/F/C% of 15/25/60%
  • The average maintenance calories for all participants was 2414 cals. 
  • Overfed ~40% of calories or ~950 cal/day for 8 weeks.
  • Carbs in the overfeed were slightly less than absolute amount at baseline, and were 40% of total overfeed calories.
  • Total caloric intake for overfeed averaged 3375 cal/day, where excess calories came from fat and protein only.
  •  The macro ratios of the overfeed diets in P/F/C% were: LP-6/52/42, NP-15/44/41 and HP-26/33/41.
Below is the summary table I made for the calories and absolute quantities (grams) of the three macros:

Essentially the low protein group received all of their caloric excess as fat, and actually cut absolute protein intake significantly (45% reduction from baseline despite overfeed), while the high protein group's excess was evenly split between fat and protein.  The absolute carb intake was effectively held constant.

Here's what happened:

They all gained roughly 7.5 lbs of fat, but the normal and high protein groups gained a lot more weight!  These two groups put on statistically similar roughly 6.5 lbs of fat-free mass while the low protein group managed to lose around a pound.  As a result, the normal and high protein groups gained roughly twice as much WEIGHT as the low protein group.

The normal and high protein groups gained around 14 lbs in 8 weeks of an almost 1000 cal/day surplus, while the low protein group gained just 7 lbs.   Now to me the low protein intervention is "artificial" as most people would have a hard time overeating and reducing their protein intake concurrently in real life circumstances of a "Western diet".   I'm not saying it can't be done, but a net reduction in protein during an overfeed to achieve 6% would require careful food selection.    Meanwhile, the normal protein group was about what we often see in clinical trials when baseline, weight-stable intake is assessed in a verifiable manner:  15% protein, 44% fat and 41% carbs is not far from what Hite & Food Litigator Economists or Nina Teicholz (or countless others) claim we were eating before low fat caused an obesity epidemic.  This is very easily how the "freshman 15" could come about with a selection of "normal foods".

Population-wide obesity is almost always assessed by BMI, so it is weight that matters (in the statistics), not the composition of the tissue adding the weight.     Given that the SAD is high in animal foods -- burgers, pizza with cheese and meat toppings, etc. -- according to this study, as much as half of a person's excess weight might NOT be fat tissue!  This is a gross oversimplification, and I'm sure that over time with less acute overfeeding, there is a re-apportioning of excesses to adipose tissue.   Still:

  • Where/what is this "lean mass"? , and 
  • When you lose weight, do you really want to lose just the fat you gained?

A few numbers:

If a 120 lb woman starts at 25% body fat, that's 30 lbs of fat and 90 lbs lean to begin with.  If she gains 100 lbs at 65% fat and 35% lean, she'll weigh 220 lbs of which 95 lbs are fat and 125 lbs lean for 43% body fat.    If she then loses only half that, preserving lean for a loss of 40 lbs fat and 10 lbs lean, her final weight is 170 lbs, 55 lbs fat and 115 lbs lean for 32% fat.  If she lost 75 lbs in similar fashion, she's at 145 lbs, 35 lbs fat and 110 lbs lean for only 24% body fat.

I'm willing to lay odds that this 145 lb woman looks nowhere near as lean as her former 120 lb self despite slightly lower body fat.  In 5 lb increments lost 4:1 fat:lean as above, she'd go to 22%, then 20%, 18%, 15% and if she gets to 120 lbs, she's at only 12.5% fat.

I probably should put this in a table, but just don't have the time at the moment.   The major point here being that the reduced weight woman will be "leaner", not because of lower total body fat mass, but by virtue of retaining fat free mass.

Where/what is this "lean mass"?

While those who are obese concurrent with sarcopenia would have an interest in preserving lean mass, there are many -- likely more -- obese people who are quite strong and "solid".  Indeed if an obese person remains reasonably active, as many do, they are "working out" all day, every day to some extent.  It is also known that bones grow/remodel in response to stress, so that it is not at all unusual for an obese person to have excellent bone density even if they don't intentionally engage in exercise.  

But without training, these lean mass increases aren't going to be gains in muscle mass of the aesthetic variety.  Without specific training you aren't getting those "gainz".   I think it's also fair to say that in only 8 weeks and a load increase of under 15 lbs is not likely to alter bone physiology much.  A third option is increase in organ size and "support" tissue, but again, this is something that would develop over time and clearly the low protein group didn't build the same.

So where does that leave us with Bray?  While we don't store protein (amino acids) per se, clearly the body is "retaining" some of the excesses here in some sort of tissue.  A little more all around with the concurrent cellular water?   It would be interesting to assess just what this "lean mass gain" was.  It does seem a no-brainer that if weight gain continued and persisted there is certainly more than enough building material lying around to increase cell numbers, organ sizes, vasculature, bones, etc.    The more important question then becomes ...

When you lose weight, do you really want to lose just the fat you gained?

The logical answer, it seems to me, is that you'd want to lose both.  There is an obsession in the weight loss industry with preserving lean mass.  This stems from two camps, I believe:

  1. The fitness industry seems to be dominated more of late by advocates of resistance training (vs. the aerobic conditioning focus in the 80s and 90s).  Therefore the bodybuilding industry is having a greater general impact on the industry as a whole.  Bodybuilders purposely go through "bulking" and "cutting" phases where they intentionally overeat -- with the goal of putting on more lean and as little fat along with it as possible -- and then stringently diet in the hopes of losing as much fat while preserving every ounce of their hard fought gainz.  This makes sense if that is your goal.  More importantly if you have fought to *intentionally* add lean mass.   But these folks are training during their bulking and putting on actual muscle.  This is almost assuredly not what went on in Bray.  If all you needed to do to build actual muscle was eat more protein wouldn't that be nice?    I'm actively engaged with this community on Facebook, and follow (or try to follow, there's only so much you can immerse yourself in) along with the science-based hypertrophy and protein consumption discussions.  You need the protein to enable the lean gains is my major take-away from Bray and my rudimentary understanding of bodybuilding.
  2. The  metabolism camp -- the one that emphasizes the caloric expenditure of muscle vs. fat mass.  Here's where I think a little science has gone a bit off the rails.  Yes, when you look at the caloric expenditure studies you can get better fits for mathematical models based on lean mass vs. total body mass, etc.  Much in the same way that factoring in age, gender, height, etc. may improve a model.  But let's boil this down to the math for a person at a normal weight.   So your average 5'4" 130 lb woman.  If she's 15% fat that's 19.5 lbs of fat.  If she's 30% fat at the same weight, that's 39 lbs of fat.  We're talking a difference of 20 lbs of fat vs. lean.  Granted this can have a major impact on aesthetics, but we're perhaps talking about 100 cal/day difference in the energy expenditure resulting from that huge difference in body composition.   Reality is unlikely to be close to that extreme, perhaps a difference of 5 lbs.  Now if that woman was 200 lbs and 40% fat (80 lbs fat to start), and maintains lean mass as she loses fat, she may well end up at 150 lbs instead of 130.   Is the 20 lb of solid lean mean fat burning machine mass doing her much good?

It may not be ...

Let's put it another way.  If that 200 lb 40% fat woman lost 60 lbs of her 80 lbs of fat and only 10 lbs of lean, she'd get to 130 and be 15% fat (that's low for a woman).  What's more likely to happen if she loses in those ratios she ends up losing 45 lbs fat and 5 lbs of lean to be 150 lbs at a very respectable 23% body fat (that's higher end of "fitness" range) and perhaps that's when her body fights back more.  This is not a speculation I can back with studies and links, it's a hunch based on personal experience and observation.  We are led to believe that she'll retain more "metabolic capacity" with the 115 lbs of fat free mass, and she still has plenty of fat from an absolute standpoint -- 35 lbs.  But this may be the reality of many of the formerly obese we keep thinking have fat cells crying out for a refill.  It may not be that at all.   It might be the lean mass that signals "feed me" and/or the body is somehow perceiving this mismatch?  It's certainly plausible.

The Biggest Loser Study 

I promise that some day I'll finish off my manifesto on that study about regain, etc. in TBL.  But many of the female participants started in the high 200s and average percent fat for all participants was around 50%.  I looked up a few of them but don't have time to detail that here.  But a 5'5" woman who should weigh like 130-150 on the high end, and ends up at 270 lbs/50% body fat has 135 lbs of lean mass.  If she's going to be 25% body fat at 140, her lean mass would be 105 lbs and she needs to lose 30 lbs of lean mass.    The average FFM loss for the group was only around 10 kg (25 lbs) and probably the smaller women (there were some very large men in this group starting over 150 lbs heavier than the women) lost less.  Who knows, what to make of the change in energy expenditure.  I'm not sure this adaptation is all it's being interpreted to be, but we do know that preserving lean mass didn't protect these participants from metabolic slowdown that's for sure!

There is another study comparing some of these participants matched to gastric bypass subjects with similar weight loss over a longer period.  The GBP subjects retained metabolic rate despite losing more lean mass.  So at least this set of studies counters the rationale that retaining lean mass helps maintain a higher metabolic rate.  Back a few years ago when I was looking at all manner of studies about metabolic rate, I found the results to be all over the map.

If you are your typical 150 lb woman looking to lose 20 lbs, chances are you don't have a whole lot of lean mass to lose.   If you are a 250 lb woman looking to lose 120 lbs, chances are you do.

Protein and Weight Loss:

Long time readers of this blog probably know I've been a huge "fan" of protein -- insofar as I'm a fan of any macronutrient.  I do still believe that the "failure" of your basic 12-15-1800 cal/day "balanced diet" is due in large part to keeping protein constant as a percent.  Your typical weight loss diet for women is around 1200 cal/day, and 15% of that amounts to only 45 grams of protein.  The 1800 cal/day diet typical for men is only 68 grams of protein.

Now I do use that word "only" in context here.  I've seen too many studies verifying the habitual diets of different human cultures, as well as metabolic ward and other well-administered-for-compliance clinical trials, that cast doubt on minimum daily requirements for protein.  While most of my fitness friends will likely cringe at these numbers, many in the plant-base communities would deem them sufficient.   More than any other macro, protein really deserves to be treated as some sort of collection of sub-macros in that we require certain specific amino acids more than others.   The fact that we excrete nitrogen in urine is evidence of a good chunk of daily amino acid intake being metabolized for fuel rather than being used as building blocks for tissues and other proteins such as enzymes and hormones.   At the very least, there's a constant cycling and recycling of an amino acid "pool" that often seems to defy expectations based on protein consumption.

Still, I subscribe to the idea of a proteostat of some sort regarding intake and satiety.  On low carb diets, it's been shown time and again that protein and fat are spontaneously "maintained" at pre-diet levels (NOT generally increased) while carbs and calories are cut.  This is almost assuredly responsible for the fairly well-documented satiety, etc. early on.    Protein and satiety are well linked experimentally regardless of carb content of the diet.  Low carb seems to work quite well for the more obese, but moreso -- look around -- ends up leaving women, especially, plateauing out at much higher weights than "normal".  Men, who naturally have lower body fat percentages, seem to fare better.  Could there be something in what I've discussed here?    The long time low carbers jumping on the keto or fat fast wagon and limiting protein?  Seems plausible this is what is/was behind the renewed weight loss in some.   Initially it may do well to "feed the proteostat", but at some point a cut in protein may be in order?

In Summary:

It appears that "normal" -- 15% -- protein is sufficient to pack on the pounds in caloric surplus.   These pounds are not just the fat from the caloric excess, but "tissue" of some sort.  The higher amino acid load is causing some storage of something and it is not likely to be simply water or it should be lost rapidly regardless of dietary or activity approach.    Furthermore, it is animal proteins that seem to be more growth promoting, and are the major source in SAD-style diets.   It's educated conjecture, but I think that high animal protein intakes prevent the body from breaking down "lean mass" in an otherwise catabolic state.   If  you're a body builder and that lean mass is hard fought for increases in skeletal muscle, then that's a good thing.

If, however, you've lost a considerable amount of weight, seem to weigh a lot for your physical size, and have difficulty getting below some reduced weight, it may just be that you are fighting with your lean mass.   And maybe, just maybe, if there is anything to this metabolic adaptation and slowing, it's because your body *thinks* it's a whole lot leaner than it is, and it has gone into "starvation mode" in the physiologically mismatched context of excess protein intake.

On a personal note ....

Since drastically reducing the animal content of my diet, and not supplementing with any vegan protein powders or concoctions, I'm now 25 lbs and two legit pants sizes down (just fitting into a pair three sizes smaller!! same brand/style) from my years-long and frustrating low carb plateau.   I'm no more saggy than a middle aged woman who has now lost around 125 lbs would expect to be.  My skin is not dried and wrinkled from eating super low fat either.  My hair is awesome and I have only isolated grays (but I dye it anyway cuz I can :) ).    I maintained 20 of that for almost two months of vacations, travel and social occasions, before getting back to trying to lose the rest.  These last five pounds came off at the same rate once I got back to it from my break, and we'll see where I go from here.  (Update 1/2017:  Now down over 30 lbs from low carb plateau when I try to lose weight it comes off, there is just less motivation to do so based on how I look, feel and perform as a certain person likes to say.)

I share this because those who were around in the early days of this blog know how frustrated I was.  I didn't begin this new "journey" to purposely lose lean mass, but as I looked at several studies (I hope to flesh this topic out with several more at some point) it just kinda clicked that I think that's what's happening (along with fat).

Years ago I joked on my personal blog (that is no longer around) that I considered intentionally losing lean mass.  It was in 2009 when I was gaining a bit on Atkins induction!  I initially lost around 15 lbs in the early days doing IF.  You know why I think?  Because I just couldn't eat that much protein in the window, I was around 40-50g in the early stages and rather low calories.  EVERY voice told me NO!!!   Don't eat that few calories, get your protein in or you'll lose lean mass and tank your metabolism.   When I upped my intake, the losses stalled.   I did try many other experiments.  Can't sneeze at the maintenance, but it was frustrating to not be able to crack that "floor".

It's been a few years now since I could consider myself low carb (especially by community standards), but those old habits die hard and I was eating lower carb and higher fat.  I wasn't worrying about protein, and not eating as much as I did previously, but I was certainly over that 15% mark, enough to keep the weight stable for years.

I don't know what my metabolic rate is these days but it hasn't been damaged by eating as I do when I'm working on losing weight.  My habitual diet may include around 3 oz of animal protein (meat, poultry or seafood) two-to-four days a week, and very low fat all the time.   I don't know how many calories or grams of protein because I don't count a thing.  There's no blood sugar rollercoaster , internal starvation from all the insulin spikes, or hypoglycemic induced hangry.  I eat rice, beans, other grains, potatoes and/or lentils daily.  I eat quite a lot of fruit and as always what would be considered a lot of veggies for most people.  I also eat just about anything on occasions, usually away from home.   When I let my hair down over the past two months my weight fluctuated within less than 2 lbs that whole time, including a half pound dip down from "baseline".    Maybe my metabolic rate is not higher, but it's certainly not "depressed".

So if I were to give advice, which I'm not fond of doing, but heck, this is working for me, so I just share and say it might work for you: At some point, stop worrying so much over preserving lean mass during weight loss.  Unless you have pre-existing issues, that just might be why you're struggling so much.  And also, from a psychological point of view, I totally get being annoyed at a number that is higher than you feel it should be for your size and that can wear on you.  This also seems to be of higher prevalence in reduced low carbers.    Low carb got me a good long way, but then it stopped working and if anything I was back-sliding.  I tried it all (well, not livin la vida no food, that wasn't a thing yet, but no way I would have gone that route due to my history), it all failed to produce more than momentary and unsustainable few pound dips below the plateau.   If what I'm doing now stops working, I'll let you know, but I don't see that happening just yet.  If or when it does, I'm already at a size I could happily remain at for the rest of my life, and know that this is easy to maintain.  I'd like to weigh less for my bad ankle, and vanity at this point.  Let the hating begin -- grin.