Does cardio or weight training have long lasting effects on the metabolism?
As I mentioned in a previous post, there’s this thing called EPOC. It has been found in a variety of exercises when the intensity is sufficient. There remains the question, though, of whether consistent training that has this boost to our metabolism leads to anything that lasts beyond the hours directly following each individual training session.
Today’s journal club looks at a study that approached this question using a particular technique that allowed them to see if there was any long term enhancement to free-living metabolism. It was published in 2002 and is titled, Effects of endurance and resistance training on total daily energy expenditure in young women: A controlled randomized trial.
The study lasted 6 months and had only female participants. They had not exercised for at least 6 months prior. They were not considered “trained”. There were 3 groups. The first group continued “normal” life and was the “control” comparison. The second group did aerobic training. These participants met with trainers 3 days a week and did 45 minute sessions of cardio that varied between 80 – 95% of max heart rate (HR). I can say from experience that working within that HR range for that long is not a walk in the park. The third group did resistance exercises. The participants met with trainers 3 days a week. They did 9 exercises that hit every major muscle group and utilized weights in the 60-80% 1RM range. The exercises were the typical meat ‘n potatoes lifts. Both exercising groups also had a warm up and cool down set of activities.
Below are the starting descriptive stats for each group. As always, they’re group averages and rounded to the nearest whole number for the ease of viewing.
All of the participants had pre/post measurements taken of their scale weight, overall body composition by a DEXA scan, total daily energy expenditure (TDEE) via doubly-labeled water (DLW), resting metabolic rate (RMR), and VO2 max. The resistance training group had their 1RM strength measured before and after the study.
I’ve explained before how the RMR measurement works. To recap, it was measured as participants sat quietly for 60 minutes in the morning before they had anything to eat. I’ve had my energy expenditure measured, both at rest and while working up to my VO2 max (on both a treadmill and a stationary bike). The gist is that you wear a mask that covers your mouth and nose. The mask is connected to a device that measures the oxygen you breath in and the carbon dioxide you exhale. That info is used to calculate your energy expenditure, aka how many kcals you burn. In this study, the researchers also used the device to measure the participant’s VO2max and the ratio of fat vs carbs burned. As I said above, all of these were measured before and after the study period.
This is the first time we’ve come across the use of DLW. It’s a technique that researchers use to measure energy expenditure in free-living people. The participants drink a specific amount of water that has been labeled with stable, naturally occurring isotopes of hydrogen and oxygen. As people go about their lives and burn calories, carbon dioxide and water are made and passed from the body. The differences between the starting amounts and the body’s removal of these isotopes over a set amount of time are used to calculate the total calories burned. That provides the average TDEE in free-range people. In this study, the researchers measured the TDEE of the participants over 10 days, both before and after the study.
In order to calculate the energy expenditure of physical activity, the researchers took the measured TDEE and they subtracted the measured RMR and the established average caloric expenditure from eating food (“thermic effect of a meal”, TEE). The TEE is 10%/day. The remaining kcals provided the count of how many kcals the participants burned as they were active throughout their day.
As always, let’s cut to the chase.
There was no lasting effect of cardio or weight lifting on TDEE. Below are the results of the kcals measurements, which are the averages for the groups.
The only change found was the RMR for the resistance training group, but that increase was no different from the start when it was adjusted for the final LBM of the group. That’s to say, the resistance training group gained 3 lbs of LBM by the end of the study, which brought with it an increase of 60 kcals to the RMR. There were no other body composition changes for that group or the others.
The VO2 max for the cardio group increased significantly, by 18%. No other group had a change in VO2 max. No group had any change in their fat/carb burn ratio, either.
The resistance training group had increases in the final 1RM tests of strength, while no other group did.
Implications / Thoughts
Other studies have shown short-term enhancements to calorie burn from training, but this study did not find any in the long run. These results suggest that we only burn extra kcals if we’re keeping up with our training. That’s the case whether our VO2 is more maxed or our strength is stronger. Our total daily metabolism will not stay high if we’re not keeping active. I’ve found this to be the case for myself, empirically.
Magazines and supplement companies love to say that if we can increase our LBM, then our metabolism will increase. The increase in this study from the gained LBM was only an average of 60 kcals. Three extra lbs of LBM is a desirable amount for those of us who have been lifting for a while. That increase in RMR, though, is far from the jacked metabolism that magazines and supplement companies would have us believe.
The authors discussed that a potential explanation for no long-term enhanced metabolism may be that there was a ceiling effect. The participants, while not “trained”, were healthy and well enough to complete the study. They may have already been at their natural high end of TDEE, such that training did not boost it in a lasting way. Less fit/less healthy individuals may get a longer enhanced effect from cardio or weight lifting. Since they were not included in the study, we cannot rule that out.
This study shows that the calorie burn from training does not extend beyond the established max 72 hours of recovery. We just cannot expect to have the same “metabolic rate” if we stop our training. Any eating for our training that we may do must stop when our training also stops. None of us like to think about that, but one day we may stop training. We may just have periods of no training because we’re too busy or because we have an injury that needs to heal, and we’ll get back into the game. Either way, our TDEE will not be so great during that time off. Our body composition and health may thank us for being considerate of this study.
If you have any questions about this study or anything I said, please feel free to leave a comment. I will get back to you and others may have insight to offer, too. If you have any questions or topic suggestions that you would like answered as a post, then please email me at firstname.lastname@example.org.
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