With consistent training & a fit body, even doing 50 chin ups & 300 squats at one go can be a trivial task & even becomes more enjoyable. What earlier seemed like a herculean task soon became your Dopamine( neuro-transmitter that makes you feel good).
As we indulge in workout consistently, our bodies adapt to demands of the training: muscle grows & metabolism improves. Due to these positive adaptations, exercise becomes easier. However, does this mean that you burn fewer calories during the exercises. Do Olympic winners & star athletes require less energy as compared to a newbie runner?
If two people of identical bodyweight were to run the same distance & at the same speed, they would burn exactly the same amount of calories as per law of thermodynamics. The problem is, calories burnt during workout is only one end of spectrum
Our total daily energy expenditure(TDEE), the total amount of calories burnt is a day consists of the following:
- Activity induced energy expenditure(AEE): Energy your burn in a day due to physical activity & workout you undertook
- Resting energy expenditure or resting metabolic rate(REE): The number of calories burnt by internal reactions that maintain our body at rest.
- Diet induced energy expenditure(DEE): The number of calories used while digesting & processing food.
The more your workout, the higher is AEE while REE & DEE remains the same. This is called the additive model.
Although a lot of us lead lives with high level of physical activity, farmers & hunter gatherers have similar energy expenditure to us. Do you really think this is true? It is possible that our bodies adapt & compensate for increased physical activity? Is our TDEE regulated at fixed level just as we tightly control our body temperature.
As per a recent study, total energy expenditure begins to plateau with extensive training. Although, it is right to say that we burn more calories during exercise- we burns higher number of calories through AEE , REE subsided- we burn less calories when not exercising
What are the reasons for this theory? Again it is our body’s adaptation to training. A lower resting metabolic rate is efficient since more energy from food is used to converted for use by cells in our body & less is wasted as heat. With long term exercise, our body endeavours to boost this efficiency- wasting less energy as heat & converting a greater proportion to be used by muscle.
Trained muscle produces less of uncoupling protein compared to untrained muscles. These proteins encoded by UCP genes serve to uncouple cell respiration from production of chemical energy instead dissipating as heat. As your trained muscles become more efficient, they express less uncoupling protein ( UCP3), thereby making a greater fraction of energy available for muscle contraction & doing mechanical work.
Considering this compensatory reduction in resting metabolic rate, total energy expenditure follow a restrained model-it does not rise linearly with physical activity rather start to tail off beyond a point.
When we have intense workout sessions at the gym or at home, we compensate for it later by moving less. We stand up for less duration & we change posture less frequently. As far as calories are concerned all these activities start for add up. Increase in exercises are partially offset by a decrease in non-purposeful muscle activity like fidgeting & change in postures.
Key takeaway
Total energy expenditure is one aspect, how, when & what you eat also have a great bearing on your energy expenditure. If your fitness goal weight loss, none of the above discussion suggest you to give up exercise after a certain point in time. A potential low & efficient resting metabolic rate is good for your body since high metabolic rate can impair your muscle building & weight loss.
Depending on your genetic code-which version of UCP you carry, game plans such as HIIT & intermittent fasting can help you optimise your metabolism.
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