How Much Do You Really Know About Your Metabolism?

Metabolism. A mysterious, complex force that many of us talk about, but perhaps few really understand…

When we think about metabolism, the discussion often turns to it’s effect on our weight. But in reality, our metabolism is much more than that!

A quick disclaimer: Some parts of this article deal with weight loss. If this type of information doesn’t jive with your current health goals, please feel free to check out some of my other articles instead!

By definition, Metabolism is the chemical processes that occur within a living organism in order to maintain life. To put it simply, metabolism is all of our body’s cells going about their daily business. Building new cells, producing enzymes and hormones, allowing us to breathe, digest, feel, and think – all of these processes in the body add up to what we simply call our “metabolism”. Each of these things requires energy in order for them to occur. The type of energy we use to refer to discussions about metabolism is calories. (A calorie is a unit of energy – specifically the amount of energy that is required to raise the temperature of 1 gram of water by 1 degree Celsius). Science!

In the nutrition and fitness world though, metabolism has taken on a bit of a different definition. Headlines touting various diets or supplements for their metabolism boosting power suggests that metabolism is the sole driving force behind weight and if we could just get our metabolism going- we’d reach our weight loss goals in no time.

So, now that you know what metabolism is, can you correctly guess the answers to this metabolism quiz?

How Much Do You Really Know About Your Metabolism?

Try to correctly guess the answer to these true or false questions. Scroll down to see the answers!

1. Genetics don’t play a role in our metabolic rate

2. People who have a hard time losing weight probably have a slower metabolism than everyone else

3. Intermittent Fasting boosts metabolism, which is why it works so well for weight loss

4. Eating 6 small meals per day boosts metabolism and is the best way to lose weight

5. Taking vitamin or mineral supplements can boost metabolism and enhance weight loss

6. Strength training increases muscle mass which boosts metabolism

7. The reason why people often have trouble “keeping it off” after they lose weight is because weight loss actually decreases metabolism

Check out the answers to the quiz below!

1. Genetics don’t play a role in our metabolic rate


There are definitely some genetic factors that play a role in our metabolic rate. Some genes can actually directly affect a person’s resting metabolic rate (RMR), while other genetic factors can influence a person’s RMR in a more indirect way. From a strictly mathematical perspective, your height really is the most predictive aspect of your overall metabolism- When we calculate an estimated RMR using your height, weight, and age, how tall you are has the biggest influence on that number. But, there is also a specific gene that has been identified which influences our metabolism. A variation of the UCP1 gene can cause someone’s metabolism to be slower than what would be predicted by the mathematical equations. People with the GG or GA allele of one of the sections of this gene (called SNPs) can have a metabolic rate approximately 150 calories less than we would predict. It may not seem like much, but could be a factor in why some people have a difficult time losing weight despite eating what we think is an appropriate number of calories.

Interestingly, the size of one’s internal organs has also been given credit for some of the person to person variation we see in our RMRs- cool eh?

2. People who have a hard time losing weight probably have a slower metabolism than everyone else


I mean, maybe they do (like I discussed in the previous question), BUT it’s important to remember that your resting metabolic rate (RMR) is only part of the energy balance equation. Exercise and energy input (ie- the food we eat) are other factors we need to take into consideration when talking about weight loss.

While we’re on the subject of energy balance… is the concept of calories in calories out (CICO) a myth?

The idea of CICO being false is often perpetuated by folks with diet books to sell. They love to claim that with their eating program you can eat as MUCH as you want, never count calories, never feel hungry, yet effortlessly lose weight…that’s a pretty tall order in my opinion! Unfortunately absolutely none of that is backed by science. There has yet to be a research study published that disproves the fact that one must reduce calorie intake in order to experience weight loss.

There have been plenty of tricks developed over the years to psychologically make us THINK we’re consuming fewer calories (such as restricting timing of meals or removing large numbers of foods from our diet, or taking appetite-suppressing supplements), but the fact is when we do studies that look at different diets and their weight loss outcomes, it’s always an overall reduction in calories that causes a person to lose weight. Always.

So, we know in order to lose weight a calorie reduction is necessary. So if it’s just that simple why is weight loss so hard?

The problem is that it can be challenging to really know exactly how many calories we eat and burn each day. We also need consistency over time to actually see weight loss occur. The method of CICO isn’t false, it’s just that we don’t have great methods of knowing exactly how many calories we burn in a day, or even really how many calories are in the food we eat, especially outside of a laboratory setting. The methods we do have (like apps for tracking intake or fitness tracking devices) are a good estimate, and work well in most cases, but if small inconsistencies add up over weeks and months, we can wind up disappointed.

Which brings me to another important point…

Calories on workout machines can be terribly inaccurate. Like REALLY, REALLY inaccurate.

The trouble with the calorie counting features on fitness equipment is that the machine collects relatively little information about you (if any) in order to give you feedback on the calories you’ve burned. How physically fit you already are, your height, weight, and muscle mass will all influence the actual number of calories you expend while doing a workout. Most people are actually very surprised at how FEW calories they burn during a workout, especially when compared to how easy it is to eat that many calories in a sitting.

For example in a 60 minute walk on my treadmill yesterday (moderate pace) the treadmill estimated that I burned 490 calories. My Fitbit on the other hand says I only burned 385 calories. If I were using the treadmill numbers to guide my “calories in” I may not see the changes I’m expecting. So accuracy is key!

3. Intermittent Fasting boosts metabolism, which is why it works so well for weight loss


Unfortunately, this one just isn’t true. Intermittent fasting has no effect on metabolic rate and any weight loss experienced while following this pattern of eating is strictly from eating fewer calories throughout the course of the day. You can read more about IF and it’s effects here.

4. Eating 6 small meals per day boosts metabolism and is the best way to lose weight


The concept of 6 small meals per day boosting metabolism is a bit of a myth as well. The idea that more frequent eating in smaller quantities keeps our metabolism running at a higher rate is definitely not valid, and snacking all day could actually lead to excess calories being consumed if we’re not being mindful about our choices. You’ve probably made the connection by now that few things really influence our metabolic rate to any meaningful degree, and that it’s our total energy balance throughout the days, weeks, and months that really matters when it comes to our weight.

What’s really important is listening to our bodies and paying attention to our hunger and satiety signals. Whether we eat only 3 meals per day, or eat 6 smaller meals/snacks if we’re in a slightly negative energy balance we will see weight loss occur. The opposite is true as well where if we’re consuming more calories than we burn. Finding the meal pattern that is sustainable for you long-term is critical for success!

Fun fact: Did you know that eating any food at all actually boosts your metabolism? It’s true! It’s called the “thermic effect of food”, and encompasses the energy required for the body to digest and absorb nutrients from a meal. It’s the equivalent of about 10% of our metabolic rate each day, so for most people between 120 and 200 calories each day. Eating specific foods or following a certain diet has no effect on this process, it’s just part of the overall metabolic picture. If a company or diet book promises you a “metabolism boost” from their eating according to their plan, it’s BS.

5. Taking vitamin or mineral supplements can boost metabolism and therefore enhance weight loss


This one can be a bit tricky because as I mentioned in the intro to this article, the way we think about metabolism in terms of our weight is only part of the overall metabolism picture. Certain vitamins and minerals are key in the metabolic processes that take place at the cellular level within our bodies- so all of those chemical reactions that are going on each day within our bodies’ cells require vitamins and minerals in order to occur. One example is Vitamin B12. Vitamin B12 does a lot of really important things in our bodies, and one of the roles it plays is in the energy production in our cells. So the chemical energy that keeps our cells alive and functioning. Now, this chemical energy is NOT the same as the mental energy or alertness that we all want to feel throughout the day. If we become deficient in vitamin B12 some of the effects do include fatigue and muscle weakness, which can be rectified with B12 supplementation, but unfortunately taking additional vitamins and minerals in the absence of a clinical deficiency is not going to make us feel any more energized – and certainly not going to cause us to lose any weight.

However, for many supplement companies this concept is a bit of a marketing goldmine. Everyone wants to feel more energetic, and everyone is looking to boost their metabolism. So sticking these buzzwords on your B-vitamin supplement label is a fantastic way to sell product. But buyer beware on this one! Always talk to a registered Dietitian before spending money on supplements to determine which ones are right for you and which are just a waste of money

6. Strength training increases muscle mass which boosts metabolism


Finally, one that isn’t a myth!

Lifting weights regularly increases the muscle mass on our bodies, which in turn increases the daily energy our bodies need to function. This is because muscle tissue is slightly more metabolically active than fat tissue is, meaning that each pound of muscle on our bodies requires more calories each day to maintain it vs each pound of fat. The difference at rest isn’t huge (about 6 calories for muscle vs 2 calories for fat), but if you also take into account the exercise that needs to be done in order to BUILD that muscle, I’m all for it. Especially since there are so many benefits of physical activity and strength training way beyond weight that we should all make an effort to get more active!

7. The reason why people often have trouble “keeping it off” after they lose weight is because weight loss actually decreases metabolism

TRUE! Well, it can be one of several reasons anyway!

Since you already know now that our metabolic rate is largely determined by our body size, obviously a change in that body size will have an impact on our metabolic rate. You can see this demonstrated in the calculations we use to estimate someone’s metabolic rate. As someone loses weight, their metabolic rate is decreased, which in turn means they may need to further reduce calories in order to continue to see weight loss (or, increase their output with physical activity!). However, this can be a tricky balancing act and unfortunately I often see clients who overdo it on the calorie reduction and wind up undereating and getting absolutely nowhere. So, if weight loss is your goal please work with an experienced Registered Dietitian who can help you find the right balance to ensure you reach your goals!

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