Tuesday, February 16, 2016

Short-term Metabolic Adaptation: Why Moving More Doesn’t Help with Weight Loss.

By: Andrew Jagim

We have previously described how throughout the process of losing weight our metabolisms undergo a negative adaptation in such a way that makes it challenging to continue losing weight and/or keep it off.  This adaptation is typically referred to as metabolic adaptation or adaptive thermogenesis.  A previously published study found evidence of how this adaptive response appears to occur even within our daily energy balance continuum and again provides evidence of just how “good” the body is at maintaining homeostasis. Unfortunately we do not always perceive this as a good thing as this ability to resist change is one of the many reasons that weight loss is a fickle beast.  Also, this adaptation is just another reason why the mantra “eat less, move more” that is often shouted at individuals who pose questions on how what strategies they can utilize to help them lose weight just doesn't work; as we’ve mentioned previous times before, this overly simplified strategy is clearly not successful, particularly long-term and here is just one of many reasons why:

The researchers who conducted this study found that when activity levels increased above moderate levels, total daily energy expenditure appeared to plateau rather than continually increase in a linear fashion, which would be expected, particularly if you believe moving more is the answer to weight loss as it would theoretically mean you are burning more calories throughout the day...Guess again: 

What appears to happen is that our bodies slow down our metabolic rate, even though we may be moving more (see figure on left).  One can assume this is some sort of survival mechanism in which our bodies perceive that we are in a high energy-demanding environment and we may need to save our energy for periods of famine or continued high activity so we better preserve what fuel (aka stored as potential energy, or calorie reserves) we have left.  This is a direct quote from the article:

Constrained total energy expenditure model, in which total energy expenditure increases with physical activity at low activity levels but plateaus at higher activity levels as the body adapts to maintain total energy expenditure within a narrow range.”

Clearly one cannot simply continue to move more and expect to "burn" more. We see this at play when individuals participate in excessive sessions of slow, steady-state cardio and expect infinite improvements in body composition and weight loss.

Although purely speculative at this point in time, I would presume this is how athletes are able to maintain a relatively stable body weight throughout the rigors of a season even though they tend to severely under-eat per their recommended energy needs based on predictive models; which in their case is a good thing.

So how do we avoid this? Is it pointless to exercise and move more throughout the day? No, being active still offers a lot of positive health-related benefits, you just can't solely rely on this for daily calorie expenditure and weight loss.  Instead, focus more on different strategies to increase your resting metabolism throughout the day which makes up a large majority of your daily calorie expenditure (60-70%).  Strategies such as strength training, high-intensity interval training and increasing your protein intake can all help to further increase daily energy expenditure and avoid this daily metabolic adaptive response.

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