Physical Activity and Weight Loss

One of the big debates you’ll see is whether physical activity is beneficial for weight loss. The reasoning is usually based on calories in vs. calories out: “if you walk for half an hour you might burn 150 calories. You take in more than that by eating one doughnut”. My first thought is “Uh, don’t eat the doughnut?” But I also think this argument is missing the main benefits of exercise, which go beyond calorie burning. It has various overall health benefits, as well as several for weight loss besides calorie burning:

  • It decreases insulin resistance [1], by various mechanisms, one of which is an improvement in density and function of mitochondria (the energy powerhouses in our cells that help us use oxygen) [2,3,4]. Less IR means less cravings (among other good things), making it easier to adhere to a better diet.
  • Resistance training and higher intensity exercise can raise resting metabolic rate for a prolonged period after the training is over [5,6].
  • All types of exercise can reduce the decline in resting metabolic rate that accompanies weight loss [7].
  • Resistance training helps preserve muscle mass during weight loss [8].
  • Being physically active can help lower the body’s metabolic set point over time, allowing a lower weight to be maintained [9].

How much you should exercise while also trying to change your way of eating is controversial. Many authors feel that if you are already active, fine, keep up what you are doing, but now would not be a good time to introduce a new exercise routine. The idea is that we only have so much willpower and would be dividing it up between being disciplined about what you are eating and disciplined about exercising.

There is some counter evidence to this, however, that showed greater long term success for people modifying their eating habits while simultaneously modifying their physical activity compared to those who modified their eating first and only added physical activity a few months later [10]. I would suspect this to be especially true for resistance training and HIIT based on the “the anti-aging and metabolic benefits of resistance training and HIIT” below.

I think it’s a good idea to at least work on bumping up NEAT through your activities of daily living while working on healthier eating. It will get you some of the metabolic benefits of being active without requiring as much discipline.

I have always been physically active any time I tried to lose weight or change my eating, so I can’t comment from experience on trying to start a new exercise program while also trying to change my eating habits. But I do know from experience about the trap of thinking of exercise primarily as a way of burning calories. I have exercised a sensible amount that’s enjoyable for me, say an hour a day, with mostly easy days and a couple of hard days thrown in. Then maybe I would do well on the scale that week. The lesson should have been, you’re doing fine, keep up the good work. Instead I’d get excited and say, “Wow I could do even better if I worked out more! I’ll burn a couple more thousand calories next week by exercising longer and throwing in some more hard days”. The next week I’d either slip up on my eating discipline and not lose any weight, or get discouraged because I was disciplined about eating and exercise but lost less than I expected. One time, I carefully measured everything I ate, and worked out for over 90 minutes a day with several “hard days”. At the end of the week I got discouraged because I “only” lost 2½ pounds! This is all short-term thinking, similar to the mindset of “being on a diet”. The long view, for both eating and physical activity, works better: Exercise is for healthy aging and a good metabolism, not to make the needle move on the scale.

The Anti-aging and Metabolic Benefits of Resistance Training and HIIT Accumulating research is showing strong evidence that the health and anti-aging benefits of exercise are even better for resistance training and higher intensity cardio (HIIT). There is a good discussion of this in Jonathan Bailor’s The Calorie Myth. There is also a nice overview of the literature in [11].

Resistance training has a dramatic effect on muscle, both by reversing sarcopenia (muscle loss), and improving mitochondrial activity (the mitochondria are the energy powerhouses in our cells, especially important in muscles) [12,13,14]. HIIT is more effective than lower intensity cardio to lower insulin resistance [15], reduce metabolic syndrome [16], and reduce dangerous visceral fat [17], and improve cardiovascular risk factors [18].

  1. Bollinger, Lance M, and LaFontaine, Tom, “Exercise and Insulin Resistance:, Strength & Conditioning Journal, 2011
  2. Groennebaek, T, Vissing, K “Impact of Resistance Training on Skeletal Muscle Mitochondrial Biogenesis, Content, and Function”, Front Physiol., 2017
  3. Little, J, et al, “Low-volume high-intensity interval training reduces hyperglycemia and increases muscle mitochondrial capacity in patients with type 2 diabetes”, Journal of Applied Physiology, 2011
  4. Menshikova, E, et al, “Effects of Exercise on Mitochondrial Content and Function in Aging Human Skeletal Muscle”, The Journals of Gerontology, 2006
  5. Hunter, G, McCarthy, Bamman, M,”Effects of Resistance Training on Older Adults”, Sports Medicine, 2004
  6. Campbell W, et al, “Increased energy requirements and changes in body composition with resistance training in older adults.”, Am J Clin Nutr., 1994
  7. Broeder, C, et al, “The effects of either high-intensity resistance or endurance training on resting metabolic rate”, The American Journal of Clinical Nutrition, 1992
  8. Hunter, G, et al, “Resistance Training Conserves Fat‐free Mass and Resting Energy Expenditure Following Weight Loss”, Obesity, 2002
  9. Guyenet, S, The Hungry Brain: Outsmarting the Instincts That Make Us Overeat, Flatiron Books, 2017
  10. King, A., et al, “Behavioral impacts of sequentially versus simultaneously delivered dietary plus physical activity interventions: the CALM Trial”, Annals of Behavioral Medicine, 2013
  11. Coyle, E, “Very Intense Exercise-Training Is Extremely Potent and Time Efficient: A Reminder.” J Appl Physiol., 2005
  12. Burgomaster, K, et al, “Six sessions of sprint interval training increases muscle oxidative potential and cycle endurance capacity in humans”, J Appl Phys, 2005
  13. Melov, S, et al, “Resistance Exercise Reverses Aging in Human Skeletal Muscle”, Plos One, 2007
  14. Bruce C, et al, “Muscle oxidative capacity is a better predictor of insulin sensitivity than lipid status”, J Clin Endocrinol Metab., 2003
  15. Babraj J, et al “Extremely short duration high intensity interval training substantially improves insulin action in young healthy males”, BMC Endocr, 2009
  16. Gilligan, L, et al, “Aerobic Interval Training vs. Continuous Moderate Exercise in the Metabolic Syndrome of Rats Artificially Selected for Low Aerobic Capacity.” Cardiovasc Res, 2009
  17. Gaesser, G and Weltman, A, “Effect of Exercise Training Intensity on Abdominal Visceral Fat and Body Composition”, Med Sci Sports Exer, 2008
    Lee, I, et al;. “Relative Intensity of Physical Activity and Risk of Coronary Heart Disease.” Circulation, 2003

20 thoughts on “Physical Activity and Weight Loss

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