We’ve talked about metabolism before on the blog many times in varying ways, but we wanted to clear up some misconceptions about how our body works, and more specifically, how the metabolism works to help you understand how to best get it to work for you.
The word metabolism gets thrown around a lot, like it is something that you can just chug a drink, or take a pill and manipulate easily to burn more calories and lose weight. There are a few methods that can most definitely cause a ‘healthier’ metabolism, which we’ll get to, but the body’s metabolism is actually still a somewhat mysterious topic that researchers are continuing to work to understand.
There is still a lot that we do know about the body’s metabolism, so we wanted to share the 4 things you need to know about the metabolism to help you get the most out of your nutrition, your training, and more importantly, feel your best!
Unfortunately, for females especially, there is this belief that we must eat as little as possible to lose weight. We regularly see diets that are 1200 calories or less, no matter how much you weigh. For us to be able to portray why this amount of calories is not enough for any adult human for prolonged periods of time, we must first understand our basal metabolic rate.
The basal metabolic rate is the amount of energy the body burns at rest each day. Basically, if you were to lay in bed all day, it is the number of calories required for the brain and central nervous system, heart, kidneys, liver, lungs, muscles, and skin to function properly (SOURCE). This can be extremely hard to measure with 100% accuracy, but utilizing a body-fat scanner, like an InBody machine or a DexaScan can get most people a pretty good idea.
The things that mostly determine this are your age, height, weight, and lean muscle mass. In one study, they measured that females have, on average, a basal metabolic rate of about 1300 calories, and males were about 1900 calories [1].
That isonly to keep your body functioning at rest, that does not include the thermic effect of food, the exercise we do, and the daily movement like our 10,000 steps we get in. When you add all of these things together, a female's total calorie burn can range anywhere from 1700-2400+ calories/day, where males can range 2500-3000+!
This is precisely why we cannot eat 1200 or less calories per day and expect effective, long-term weight loss without our body adapting negatively.
Wait, what? But, my fitbit told me that the 3 hours of exercise I do each day burns 4000+ calories! Our question is always - are you still struggling with your weight? And the response is usually a resounding yes. So why? Why can we not just ‘burn off’ the 800 calorie cinnamon roll we indulged on at breakfast?
Well, from what research seems to show us, the metabolism is not additive in nature, it is actually adaptive and compensatory. This means that when we continue to work out more, and more, the body doesn’t actually burn more and more, it compensates. This is what is known as the constrained total energy expenditure model (SOURCE). At a basic level, this is the idea that as we increase physical activity at high levels, total energy burned in a day levels off. The body does not in fact just continue to burn more and more calories, there are compensation effects that happen throughout the body to slow down your total daily burn to keep you from burning too many calories. This is known as the constrained effect, and is demonstrated with the graph below.
The one exception that the body seems to have with this is non-stressful movement - meaning walking! So instead of spending 2 hours on the treadmill or spin bike trying to sweat out 700+ calories, we recommend lifting heavy, and walking more. These two things seem to have the most beneficial effect on our metabolism.
Like we said in the beginning of this blog, the metabolism is not some mechanism that only burns calories for us to lose weight, the metabolism is actually in every cell of your body. It actually is a series of chemical processes in each cell that turn the calories from the food we eat into the fuel that literally keeps us alive. Pretty important, right?
The basal metabolic rate that we discussed earlier represents this well - it is what measures the summary of different tissues with different needs and how many calories it takes to keep them functioning (SOURCE). I don’t know about you, but I’d rather eat enough to make sure my brain, liver, and kidney have what they need to keep me going! Ever wonder why you diet for so long and you start to notice brain fog, struggling to remember things, poor sleep patterns, digestive issues, and more? This is because your body is not getting enough energy (calories) to support the function of all of these essential parts of the body!
A lot of people think that their metabolism is broken, or just genetically slow, or they were dealt a poor hand of cards at birth. We will not argue that there are some components of metabolism that are purely genetic, but there is actually quite a bit we can do to ‘speed up’ or ‘slow down’ our metabolism. The main two things that slow down metabolism are dieting and aging.
As we age, the metabolic slow down happens gradually, and it can start as young as your 20’s. Some of it has to do with how we process food, some of it has to do with muscle tissue change, but the majority of the reason is still somewhat unknown (SOURCE).
As for dieting, it seems to be the more extreme or chronic dieting that slows the resting metabolism the most significantly. We discussed this more in our blog on metabolic adaptationHERE, but as people lose weight, the energy used for basic functioning slows down quite drastically. This can best be shown by the ‘Biggest Loser Effect,’ which was the show where dozens of people lost massive amounts of weight very quickly through crash dieting and extreme exercising. When these contestants were revisited 6 years after the show, the participants' metabolisms had vastly slowed down and their bodies were burning about 500 calories LESS on average daily than would be expected given their weight, age, height, etc. This shows us that their metabolic adaptation never actually rebounded back, their metabolism stayed slower from the extreme dieting.
So if crash dieting and aging slow down the metabolism, what can increase it? The main things that bring your total daily calorie burn up, based on the research, appear to be:
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