Become a Sustainavore!

Eat for your health, the planet, and your values.

Become a Sustainavore!

Eat for your health, the planet, and your values.

Aerobic Fitness and Metabolic Health

TL;DR: Basically – you can’t work off that Big Mac, large fries and 72oz soda – diet first, then movement! Aerobic exercise is not a quick fix solution to all health problems. Instead of focusing on aerobic fitness, preventing metabolic syndrome should start with improving diet quality, which will help in controlling weight, THEN you can worry about increasing physical activity. This can happen all at once, but #1 is to focus on what you put in your mouth. The amount of fat somebody had in this study was more predictive of their risk for disease than their fitness, so that should be the initial focus in improving health. No amount of movement can outrun overconsumption.

I’m back with another study summary, and this time we are looking at aerobic exercise and its impact on overall health when measured alone.

A new study recently came out detailing how cardiorespiratory fitness (CRF), or what many people call aerobic fitness, and to the shock of many influencers on social media, its not as good a predictor of metabolic health as many have previously thought. 

This highlights a misconception I see all the time in my practice and it illustrates to you why I have a certain outlook on the balance between diet and exercise and how they relate to health. 

Think of it like this – 80/20. Diet is 80 and movement, sleep, stress, community, etc is the 20. 

This study is called “Is low cardiorespiratory fitness a feature of metabolic syndrome in children and adults?”. You can find it here. 

So, let’s get started

Goal of the Study:

Research how cardiorespiratory fitness (CRF) relates to metabolic health in both children and adults when adjusted for body size and composition. Previous studies have accessed similar metrics and have adjusted their findings for body size when looking at the relationship between CRF and metabolic health but never using body composition. Thus, their goal was to see if adjusting for body composition instead could show a different relationship between CRF and cardiometabolic disease (CMD).

Confused? Don’t worry – if you didn’t understand that I will explain it more below.

Important Terms:

Cardiorespiratory Fitness: CRF

Cardiometabolic Disease: CRD. In this study the researchers are looking at the risk someone has for metabolic and cardiac problems based on blood markers including insulin, HDL and LDL cholesterol, HOMA-IR, and triglycerides.

Adjust/Scale: In this study the authors frequently discuss how they scale one studied metric with another in the study. This is a statistical technique used in observational studies to try and remove other variables in order to determine if there is actually a relationship between two things. For example, a person with a higher body mass and lower fitness has a larger risk for CMD. Is that risk caused by the body mass, the fitness, or both? 

Previous researchers had scaled a metric of CRF (VO2 max) with body mass to determine the relationship between CRF and CMD. This looks something like this example: two people of the same weight have different VO2 max scores. The person with the higher score, and thus the higher CRF, has better blood markers and less risk of disease. Thus, their lower risk is correlated with their fitness and has nothing to do with body mass as the weight is the same between both subjects. This would show a correlation between CRF and less CMD risk. 

In a study, there is no perfect situation like that, but using statistical tools the researchers attempt to remove one variable and isolate the other. This is how past studies have found a relationship between CRF and less CMD risk.

Fat Free Mass: This is a measure of body composition. As the name says, it is the mass of the body that is not composed of fat. A common way of saying the opposite of this number is body fat percentage.

This is an essential metric in this study as some people may have the same total body mass but different fat free mass. The researchers hypothesized that this metric may be more influential on CMD than total body mass and may influence the relationship between CRF and CMD. 

What the Researchers Did:

They collected data through blood draws to get the markers for CMD, did a VO2 max test to measure CRF, measured weight, and measured body composition for children and adult men.

They then analyzed their data to analyze the correlations between the different variables.

What They Found:

When scaling the VO2 max with body mass, the findings were the same as previous studies showing a correlation between CRF and less CMD. However, when they scaled the CRF with fat free mass instead of only body mass, the association lessened considerably. 

What does this mean in plain english? It means that cardiorespiratory or aerobic fitness may not be as important as we once thought in determining risk for metabolic and cardiac disease. The most important factor in this study was the amount of fat somebody had. 

The authors suggest that low CRF is not necessarily a feature of CMD risk. Meaning, just because somebody is not aerobically fit, doesn’t mean they are at risk metabolically. 

Also, as the authors say, “Our results show that being overweight or obese increases the risk of metabolic syndrome regardless of the level of aerobic fitness.”

Why Is This Important?

This is why I believe the number one lever in improving health has to be diet and lifestyle aimed at correcting metabolic dysfunction. I don’t advise my clients just to go out and run until they are more fit without any consideration of diet, because that doesn’t work. Also, to only focus on aerobic fitness with no weight baring component (lifting) can, in some cases, actually increase hunger and make the problem worse.

As I mentioned earlier, this is a misconception some people come to me with thinking they can just exercise enough to fix their poor diet. It doesn’t work like that. 

As the authors say: “Instead of focusing on aerobic fitness, preventing metabolic syndrome should start with increasing physical activity, improving diet quality, and controlling weight.” It all has to go together.

This is important to understand as holidays are coming up. That 5k turkey trot in the morning isn’t going to fix all the pie you eat at dinner! I’m not saying you can’t ever indulge as I do it too, but we have to understand that what we eat has lasting effects regardless of anything else you do. 

This also highlights why I push back against some of the recent trends in the arena of weight loss and dieting. I am all for loving your body no matter what, but I also recognize that having excess body fat is a risk factor for cardiometabolic disease. That is simply a scientific fact.

Additionally, some common dieting advice is deeply flawed in its assumption that all food is okay as long as it is in moderation. 

These are nuanced and complex concepts in and of themselves that I may write about later. However, if you want to learn more now, checkout this documentary called Fed Up or read my book Sacred Cow where I mention these ideas.

In conclusion, despite what many in the diet and fitness industry might tell you, aerobic exercise is not the solution to metabolic disorders. A better solution is to use diet and exercise in conjunction, with the consideration of body weight, to improve the metabolic health of an individual. 

-Diana

Reference Study: https://www.jsams.org/article/S1440-2440(22)00213-4/fulltext

My posts may contain affiliate links, which means you don’t pay any more, but I may make a small commission, which helps me continue to bring you great new posts. Read my full disclosure/disclaimer here.

Enjoy This Post? Share It With Friends!

Facebook
Twitter
LinkedIn
Pinterest

1 thought on “Aerobic Fitness and Metabolic Health”

  1. I agree with everything you said here, I’d add though that the two things that jumped out to me are:
    1) The conclusion makes a lot of sense; if you’re less fat, you’re less dependent on aerobic fitness (alone) to reduce your risk of CMD; seemingly regardless of how you got there (in the kitchen, or being “fit” with other energy systems). It would be neat to see this repeated with say lactate threshold (capacity) or max force production (strength).
    2) “V̇O2peak was consistently and positively associated with high-density lipoprotein cholesterol in children and adults irrespective of the scaling approach” — needs echoed again!

Leave a Comment

Your email address will not be published. Required fields are marked *

Recent Articles

Stay Up To Date

Join 60,000+ advocates just like you!

Stay Up To Date

Join 60,000+ advocates just like you!

Scroll to Top

Sign Up for my newsletter Below, and You'll Receive Instant access to all my Free Monthly Downloads!