Constrained Total Energy Expenditure and Metabolic Adaptation

I just heard a fascinating podcast interview about energy expenditure. It connects the dots on many things that I have felt, but could not prove. If you have an hour, listen to Sigma Nutrition #208.

SNR #208: Herman Pontzer, PhD – Constrained Energy Expenditure Model & the Evolutionary Biology of Energy Balance

If you don’t have an hour, I’ve taken some notes. Afterward, I’ll give a few thoughts.

  • Dr. Herman Pontzer performed research on the Hadza population, which are 5-10 times more active than a Western population, and learned that they DO NOT burn more calories a day than far less active societies.
  • The Hadza are not more efficient in walking and sleep the same number of hours as Western society.
  • Your body adapts to your level of physical activity, so the calories you burn daily doesn’t change much as you get more active.
  • If you start a new exercise problem, you will see an increase in calorie expenditure, but the body quickly adapts.
  • Mice in the lab that work harder for food – do not burn more calories than mice that don’t.
  • Zoo and wild animals burn the same number of calories per day.
  • When you increase the physical activity component, you turn down the other components of metabolism.
  • High levels of activity reduce steroid hormone levels. The more active populations have lower testosterone levels.
  • Dr. Pontzer doesn’t think NEAT can explain the difference. The NEAT hypothesis was pre-accelerometer. Current research uses accelerometers, in which all activity is measured.
  • Diet manages weight. Exercise manages metabolism. They are not interchangeable. They are two different tools for two different jobs. 
  • This effect is called Constrained Total Energy Expenditure. The body wants to maximize use of resources, but not go over. This is likely an evolutionary adaptation for survival.

Photo by Surya Prakosa

Initial Thoughts

There are several posts going back years on this site where I am critical of the role exercise has on fat loss. I’ve always felt the cheerleaders used survivorship bias to demonstrate the effectiveness and that they didn’t look at a long enough time horizon.

When we exercise a lot, we tend to conserve energy better during periods of rest. I’ve seen this referred to as the Compensation Problem. This supports the Constrained Energy theory.

My April 2015 post Exercise and Fat Loss Revisited touches on the metabolic cost of high levels exercise. At that time, I was seeing it from a recoverability point of view. But it is all connected to what Dr. Pontzer discussed. If the other metabolic markers in my body were down-regulated during my marathon running days, then that would impact my recoverability.

The NEAT comments are fascinating, especially since I was recently won over by the 10,000 Steps argument and how NEAT can help keep weight off by compensating for a post-diet reduced metabolism.

This disconnect between what I felt about NEAT and the points raised on the podcast made me think about how Art De Vany discussed energy expenditure in nature. He is a big fan of unpredictability in movement and eating patterns. When too much regularly is part of our routine, our body becomes hyper-efficient at energy management. This might mean that breaking up NEAT into random patterns might have greater benefits than compressing that movement into predictable windows of time. This is just a guess.

It will be interesting to see how this discussion proceeds. I’m going to still be a student of The 10,000 Steps University, but I might skip class on the days when I need to focus on other health goals such as injury recovery, muscle gain, or something else I deem energy expensive be it physical or mental.

I’m also thinking about metrics such as pulse and body temperature as indicators that too much of the metabolic budget is being spent on exercise. These are points brought up by the Ray Peat followers frequently. Back in my running days, I had a low pulse rate. Like many other endurance athletes, I took pride in my 50 beat resting pulse as a sign of health. Now I know better.

Perhaps what I wrote about exercise back in 2012 was correct. Damn. Everything is coming full circle.

Your thoughts?

UPDATE Jan 2018: Part 2 is posted.

Published by

MAS

Critical MAS is the blog for Michael Allen Smith of Seattle, Washington. My interests include traditional food, fitness, economics, and web development.

14 thoughts on “Constrained Total Energy Expenditure and Metabolic Adaptation”

  1. Just followed your link to the 2012 post. It is an exercise approach that closely follows what Mark Sisson advocates (HIT and lots of low intensity movement), and was shown to be very effective by Donal “of don’t fear the fat” who did similar workouts (brief HIT 4 minutes a week). I have done variations on BBS and HIIT. BBS is great, but it really does fire up the appetite, so I don’t do it on a weekly basis.

  2. @MAS
    Maybe experiment a bit with measuring Heart Rate Variability (HRV)? Sisson has a brief explanation. Haven’t yet tried it myself.

  3. Very interesting. In my view this means one should focus primarily on resistance training and real food diet, however as psychological state affects appetite and activity may affect the long term weight set point, could resistance training alone be enough for these effects to take place?

  4. @All – My initial takeaway is to first solve for muscle, then movement, which is varied. Minimize predictable long static-state movement that is energy expensive – unless you derive enjoyment from those activities.

    Heart Rate Variability might be a tool.

    I’m going to rely on intuition for now. It seems to be working for me.

  5. @MAS
    Another issue is that while adding muscle has many benefits, the extra fat burning capacity gained by adding muscle is apparently often exagerated. See, e.g., Brad Pilon’s “How Many Calories Does a Pound of Muscle Burn?”

  6. Just finished listening. Fascinating and something I’ll need to think about for awhile.

    The host (I believe) threw out the idea that movement might assist the body in better regulating appetite. This struck home with me, because I lost weight when I started doing HIT with a personal trainer, my diet was actually pretty good, but I’d been basically weight stable at a higher number for several years.

    What was so strange was that, with no real changes to my diet, I lost a lot of weight and it mainly took the form of not wanting to eat, stopping eating shortly after I started (hungry to not hungry after eating about half of what I thought I would), and a huge and blessedly temporary aversion to desserts which was, for lack of a better word, really really weird, that lasted for about 4-6 weeks.

    The question that occurs to me is could you incorporate his discoveries into a model of exercise and weight loss where calorie burning is not the means by which exercise influences weight. Ideally this model would explain the differences between people who readily lose weight exercising and those who don’t. Perhaps it’s as simple as the speed of the response or non-response to a calories deficit as he outlined at the start of the podcast, but it could be more.

    Speaking for myself, I’ve always been fascinated by the way my body is sometimes sending me accurate useful signals about what and how much to eat and when it’s not. The Food Reward Hypothesis has some explanatory power for that sure, but could there also be a role for strength training and cardio that’s independent of the calories they burn in improving appetite regulation?

    This is a bit garbled, I suppose, but just trying to clarify my thinking by writing it out.

  7. @tml_mpls – My experience has been that of all the exercise strategies I have tried, HIT has the greatest ROI. ROI in this sense is not “return on investment”, but strength gains and body comp improvements with the least impact on appetite.

    Pavel training was good for body comp and strength, but I also had a greater appetite.

    Marathon and triathlon training was poor for body comp and had the highest impact on my appetite.

    Speculating here, but I think Yoga likely has a good ROI as well. Not hot yoga, but normal yoga.

  8. Yeah, perceived change in appetite might be a very useful shortcut for the effectiveness of an exercise intervention on weight loss.

    I’ve been playing with the idea for the last couple days that what if the entire weight loss benefit of exercise consists of favorable changes in the body’s regulatory systems, satiety hormones, lipostat etc how would that change or not change the way exercise should be approached.

    For instance, walking burns so few calories and – if I’m interpreting the podcast right – the body can adapt to it so quickly that under a calorie model of exercise it should be completely ineffective for weight loss. However, perhaps especially in a sedentary individual, the boost in activity would trigger hormonal or other changes that result in improved appetite regulation delivering a benefit.

    Alternately, when I’m lifting weights, workout frequency, duration, and reps and other proxies for calories would become a lot less important as compared with intensity, maximizing muscle recruitment, going to failure, and allowing adequate recovery time.

    The ideas are still a bit hazy, but you can google exercise and “appetite regulation” and find a lot of interesting stuff.

  9. Interesting analysis, but mildly depressing. One speculation I had was that from a survival biological/advantage perspective it would seem larger body size in general would be maladaptive for a more active person. So I theorize there could be adaptations in more active populations that lead to a reduced body size, since we would expect it easier to move a smaller body. Of course, this could mean more of a reduction in lean body mass than fat. But optimistically I suppose these findings don’t rule out the possibility that adaptations could occur when an individual becomes more active that promote long term reductions in fat. I would be curious if there were any data on fat mass changes over time in long term exercisers

  10. @Winston – Your comment reminded me of G-Flux.
    https://www.precisionnutrition.com/all-about-g-flux

    In short: The benefits from high levels of activity come when paired with high levels of calories.

    More exercise means improved nutrient partitioning, insulin sensitivity, protein turnover and tissue remodeling. More nutritious food consumption means sustained sympathetic nervous system activity, elevated metabolism, and better overall nutrient status.

    Another piece of the puzzle?

  11. I listened to this podcast and found it extremely fascinating – did some Googling, and ended up at your blog. Thanks for sharing your insights!

    I wonder what the implications would be for someone who has been highly active for several years now (i.e. twice-daily training sessions consisting of strength training and conditioning work, as well as sport-specific training). Would be interesting to see how energy expenditure would be affected if they were to drop their sport, for instance, or cut back to a more moderate training protocol (4-5 sessions of strength and/or conditioning work per week).

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