Don't be a Yo Yo! (Effect of weight change on energy expenditure)

Effects of experimental weight perturbation on skeletal muscle work efficiency, fuel utilization, and biochemistry in human subjects

Or in plain English, what happens to your metabolism when you gain or lose weight.

Maintenance of a body weight 10% above or below that “customary” for lean or obese individuals results in respective increases or decreases in the energy expended in low levels of physical activity (nonresting energy expenditure, NREE). These changes are greater than can be accounted for by the altered body weight or composition and are due mainly to altered skeletal muscle work efficiency at low levels of power generation.
We performed biochemical analysis of vastus lateralis muscle needle biopsy samples to determine whether maintenance of an altered body weight was associated with changes in skeletal muscle histomorphology. We found that the maintenance of a 10% reduced body weight was associated with significant declines in glycolytic (phosphofructokinase, PFK) enzyme activity and, in particular, in the ratio of glycolytic to oxidative (cytochrome c oxidase, COX) enzyme activity without significant changes in the activities of enzymes relevant to mitochondrial density, respiratory chain activity, or fuel transport; or in skeletal muscle fiber type or glycogen stores.
The fractional change in the ratio of PFK/COX activity in subjects following weight loss was significantly correlated with changes in the systemic respiratory exchange ratio (RER) and measures of mechanical efficiency of skeletal muscle at low workloads (pedaling a bicycle to generate 10 or 25 W of power). Thus, predictable changes in systemic skeletal muscle biochemistry accompany the maintenance of an altered body weight and account for a significant portion of the variance in skeletal muscle work efficiency and fuel utilization at reduced body weight.

One doesn't have to read this entire paper or muddle through all the enzyme names and their purposes to digest the practical implications of this paper.  We all know that recidivism rates for weight loss are  worse than those for most criminals.  I've also long believed that for many of us, women especially since we are more likely to diet earlier in life, it is dieting that makes us fatTER in the long haul.  

So let's say as a weight stable well nourished 130 lb woman I require 100 cals/day to do Activity X.  Then I gain 30 lbs over the years, so I'm a well nourished 160 lb woman who may actually require 110 cals/day to do Activity X because it involves moving around more weight.  My body senses plenty of energy supply ... it can afford a bit of inefficiency.  Then I decide to lose 30 lbs.  Kid yourselves not, if you lose 30 lbs you have reduced your energy intake and your body senses this.  Your body thinks it's a famine period and it knows not when it will all end.  So it tightens the belt, so to speak, and becomes more efficient.  So now at 130 lbs reduced, I only require 90 cals/day for Activity X.  

The finding that fat oxidation during exercise is increased following weight loss is consistent with other ergometric studies (1940) and is most likely reflective of the overall biochemical and molecular changes in skeletal muscle that produce a more chemomechanically efficient organ after weight loss. Overall, however, weight-reduced individuals have lower fat oxidation rates (3873).
Now if I eat like my former 130 lb self, I'll gain weight, and if I return to my 160 lb habits, I'll gain it faster.  But this time when I get to 160 lbs I'll may only require only 100 cal/day for Activity X.  If I'm eating at former 160lb self levels, I'm still in energy surplus at 160 lbs so I end up tacking on 10 more pounds until the cal/day for Activity X reaches 110.

Rinse, repeat = disaster.

Increasing muscle efficiency during low-level exercise combined with an increased propensity to store ingested calories as fat would function coordinately to favor the regain of lost adipose tissue.


Muata said…
I think this is why some form of progressive resistance training is a must as a form of weight loss maintenance. Cardio doesn't build muscle, and since this report indicates that skeletal muscles tend to tighten their caloric belts, then we have to give them a reason to burn more calories. Since the training is progressive in nature, the stronger the muscle becomes, it also has the potential to grow, which hopefully helps to alter the p-ratio a bit.

I don't know CS, if we've wrecked out metabolism by being obese/overweight in the past, I think this report, as well as others, shows that to keep the weight off one has to build/strengthen muscle and find more ways to "move more" (not exercise) throughout the day, especially if s/he has a sedentary job!
Sven Anders said…
This explains why at the tender of age of 36, I have to work harder and more intensly than ever before to shed weight and keep it off. Thanks, CS
CarbSane said…
Imagine being me ;) King, I can tell you that, at least in my n=1 experience, and a decade-ish more of doing this (including some larger 60-80lb+ swings) ... there is hope.

I am definitely eating more these days -- or feeling like I do which is all that really matters -- and coming up on 3 years maintenance of the bulk of my weight loss (lost more VERY slowly since, not regain).

I don't count calories or carbs or anything. I don't even "exercise" - but as Muata said I DO absolutely move MORE. I run up stairs in my house, do the parking far away deal, and as I type I'm waiting to flip my beef making beef stew. Normally I would have taken a seat. Now I'm standing, and as I go over to the stove I'm doing a silly Flashdance number. Laugh, anyone, if you will, but it WORKS!!!

The data on formerly obese are a bit depressing. But most are a few months, sometimes as little as one month, after the weight loss. If you keep it steady it gets easier. At least for me ... and I'm staring down 50!
Alan said…
ONe problem may be our distorted self-perceptions. Now we all agree that getting thinner makes us "look" better and be treated better. And that the effect-range (the y-axis) is monotonic across a VERY large thin-ness-domain (x-axis): you have to become VERY VERY VERY thin before somone says (either aloud or silently), that you look worse than before.

But i'm not so sure that the effect is LINEAR. Going from 160 to 130 is by perceived by all, as an improvement; going from 130 to 126 might not be noticed by anyone except ourself.

In other words, there may be quantum mechanics happening here.

If so, then we might be able to define "stages" of plateau wherein an improvement gets noticed.
LeonRover said…
Well, Alan,

It's more Heisenberg's Uncertainty Principle rather than Bohr's Theory of the Hydrogen Atom.

String Theory provides a more fruitful non-science for analogies.
Archibald said…
In my opinion, the reason that some of us end up doing so much weight cycling is that we are “easy losers” and are high responders to exercise but, consequently, choose to descend to unrealistic weights that we just have no hope of maintaining, in the long run, for reasons both physiological and psychological. This MAY be particularly true if we have experienced a good deal of hyperplastic obesity prior to adulthood or have been morbidly obese. While I just can't bring myself to fully endorse “weight/fat acceptance”, I like much of the “healthy-at-any-size” rationale. For sure, one needs to prove to oneself that he or she can maintain a given weight for long periods of time, even if it's not an “ideal” weight. As a champion loser myself, but an Olympic-quality regain-er, intentionally maintaining a weight much higher than what I know I can achieve is an especially hard discipline. For the “easy loser” at least, there's also the frequent attitude, I think, that weight gain doesn't matter so much because, well, it's easy to lose (and there's a lot of positive reinforcement during the down cycle) – that is until the effects of a slowing metabolism are encountered, which they will be, guaranteed.

I really like your blogs, CarbSane, and very much appreciate what you're doing even though I'm science-challenged and frequently get lost in the forest of acronyms and initialisms. I keep telling myself that the truth will set me free if the depression (or FFA) doesn't kill me in the meantime!

Archie Springer
R. K. said…
What about the concept of a 'Dieters Gone Wild' day, indulged once a week, as illustrated in Tim Ferris's slow-carb diet? Is there any science behind the concept (that an overfeeding day will reset the control mechanisms)? Would like to see you do a post on this issue, thanks.
Muata said…
@Archibald - I couldn't agree with you more. I believe the thrill of losing weight is another layer of addiction that needs to be acknowledged and discussed. No matter how many times you've lost or re-gained, once the scale starts moving in the right direction "again", we, magically, forget how many times we've seen that lower number in the past. It doesn't matter because that 5lb water loss whoosh is the hit we need to keep chasing lower numbers on the scale.

However, we can't, as you said, keep ourselves at the lower weight before our other addiction kicks in (i.e., that dirty little "g" word). The thrill of being able to eat, and eat a lot, again feels great until your pants start getting tight and the scale is no longer your friend.

It's this all or nothing attitude that we have to drop to be successful maintainers. Also, I think that we have to be utterly honest with ourselves before we even think about losing weight again. It takes work to keep the weight off, and if you're not willing to put in the work, why put your body through the stress of losing only to regain the weight again?

IDK, we have weight loss and fitness industries but, interestingly enough, no real weight maintenance industry ... the conspiracy theorist in me thinks it's a set-up ;)
CarbSane said…
Hi Archie! Thanks & welcome to my blogs! Indeed I thought long and hard (not every day but for maybe about a year after I gained back a 60+ pound loss and added on who knows how many more) before trying this one last time. The HAES movement is on to something in terms of a stable weight being better for health. I just don't like the "it can't be done" defeatist attitude I get from them. I'm not sure if I used to think gains weren't important b/c I could lose it again, so much as when things crept up a bit I would avoid accepting it until stuff snowballed.

I do think I was addicted to the thrill and compliments while losing. How did you do that? How much have you lost? You look good! Few people note that you still look good.

Keep up the good fight!
CarbSane said…
Welcome R.K.! In my experience, science-based or not, I did seem to experience those whooshes after a cheat. With LC, the metabolic state (gluconeogenesis, ketosis, etc.) is fasting/starvation so "feeding" your body periodically should keep it from feeling like it's a famine. There does seem to be a bit of truth to the eat more burn more. The trick might be to eat to approx balance so the body doesn't feel like it's in constant deficit but you don't set yourself back.