In 2010, I wrote an article that presented the difference between physical activity and exercise. At the time, I thought it would be a piece that potential readers would find redundant and unnecessary, mainly because everyone knew how to distinguish between physical activity and exercise.
It may seem simple, but even today, there is still a lot of confusion on the subject.
Not just among the general population.
Among health professionals, too.
Even within the scientific community, yes.
According to the World Health Organization, physical activity is defined as any bodily movement produced by skeletal muscles that requires energy expenditure. Physical activity refers to all movements performed, notably during leisure time, at work, or to get from one place to another.
As early as 1986, Caspersen and colleagues had proposed a very similar definition, but with some interesting clarifications: Physical activity is defined as any bodily movement produced by skeletal muscles that results in energy expenditure. Energy expenditure can be measured in kilocalories. Physical activity in daily life can be classified as occupational, sports, household, or other activities. Exercise is a subset of physical activity that is planned, structured, and repetitive, and has as a final or intermediate objective the improvement or maintenance of physical fitness. Physical fitness is a set of attributes related to health or skills. The degree to which people possess these attributes can be measured using specific tests.
We can therefore state that exercise is certainly a form of physical activity, but physical activity is not necessarily exercise.
We regularly read scientific articles that mention using physical activity as an intervention on X or Y element, when in fact it is an intervention involving exercise.
In the 2000s, I studied the effect of exercise and caloric restriction on physical activity and body composition. If physical activity and exercise were synonymous, it would have been impossible for me to conduct such a study. I could not measure the effect of a variable on itself.
Physical activity and exercise are two different things.
Yet, we regularly read and hear statements claiming that physical activity has no effect on weight, that physical activity is important for improving physical fitness, etc. When we look closely at these statements, we realize that they are actually referring to exercise, not physical activity in the strict sense of the definition.
It is true that for many, many people, exercise has relatively little effect on weight. Overall, the effects of exercise on body composition seem more interesting in terms of reducing visceral fat, but not to a sufficient extent to significantly change weight. So, it is not “false” to say that exercise, in many cases, will not have a major effect on total weight or even on total fat mass.
I should clarify that this does not mean that exercise is useless for people who want to lose weight (and even for those who do not want to!). Exercise is particularly effective for improving physical fitness. Whether it’s aerobic capacity, aerobic endurance, muscular strength, muscular endurance, flexibility, power, agility, etc., exercise was entirely and totally designed for that.
For many people, exercise generally has little or no effect on total energy expenditure. Just because we exercise does not mean we will burn more calories during the day. Also, exercise tends to stimulate appetite, especially when energy reserves are depleted. The increase in energy expenditure during exercise can be quite easily offset by an increase in appetite. This relationship is not as clear when it comes to physical activity, especially when the intensity of activities is lower.
People who train do not necessarily burn much more calories than people who do not train.
Allow me to present data from energy expenditure measurements by accelerometry (measured on the non-dominant wrist), which I have conducted in recent years.
After cleaning the data, I was able to divide a group of 147 people into two groups: 1) people who report training between 1 and 8 times per week (n=125); and 2) people who report not training (n=22), that is, people who do not engage in planned physical activity with the goal of improving their physical fitness (exercise). By comparing the size of the groups, you will see that the majority of people who consult me exercise (n=125) and a minority do not (n=22).
Let’s start with the total amount of energy expended, that is, resting metabolism plus total physical activity. I am deliberately and necessarily neglecting dietary thermogenesis because it is not measured. However, it is a negligible value in total energy expenditure, generally about 10% of total calories.
Back to our groups…
The Exercise group expends about 2392 kcal per day, while the Non-exercise group expends 2420 kcal daily. In absolute terms, both groups expend the same amount of energy daily, and if they consume the same, their weight will remain relatively stable, exercise or not.
To obtain a more specific analysis independent of body size, we can remove resting metabolism and focus on energy expenditure associated with physical activity. We might expect the Exercise group to expend 200, 300, or even 400 kcal more due to the energy expenditure associated with their training.
Let’s see…
The Exercise group performs, on average, 409 minutes of physical activity per day for an energy expenditure of 1166 kcal. The Non-exercise group completes an average of 389 minutes of physical activity per day for an energy expenditure of 1042 kcal.
Statistically speaking, we cannot distinguish a difference between the groups at this level. Exercise, in our sample, does not seem to add to daily physical activities, but rather to replace part of them. If there were an additive or cumulative effect, we would observe a greater energy expenditure of a few hundred calories for the Exercise group. This may be the case on training days.
In terms of body composition, we do not observe a significant difference in fat mass index, a measure used to assess adiposity relative to body size (for statistics enthusiasts, the effect size for this comparison is extremely small).
So, all things considered, people in the Exercise group do not seem statistically less fat than those in the Non-exercise group.
In our sample, on training days, the Exercise group performs 422 minutes of physical activity for 1223 kcal expended. That’s about 30 minutes and 200 kcal more than the Non-exercise group on a typical day. It is interesting to note that the duration of training sessions for participants in the Exercise group was rarely less than 60 minutes. We might have expected to see an increase of almost 60 minutes, instead of the 30 minutes we counted. Several factors can influence these results, from measurement error to seasonal variability in physical activity, but it remains possible that exercise is not fully cumulative.
This is where things get very interesting… (at least in my opinion)
We can split our exercise group into two: those who increase their energy expenditure on training days, and those who decrease it.
Of our 125 participants who reported training, 91 managed to increase their energy expenditure compared to their rest days. However, 34 participants had lower energy expenditure on training days compared to rest days.
On average, the group that managed to increase their energy expenditure on training days accumulated 378 kcal more than on rest days. The group that decreased reduced their energy expenditure by 214 kcal on training days compared to non-training days.
When it comes to total physical activity time, we observe an increase of 110 minutes of physical activity for the group that increases, and a decrease of 74 minutes for the group that decreases.
Now, let’s compare the body composition of participants who increase their physical activity level on training days with those who decrease it. The group that increases has a fat mass index of 5.6 kg/m², while the group that decreases has values of 7.3 kg/m². For an average-sized person, this represents a difference in fat mass of 4.3 kg (nearly 10 pounds).
It would be risky to draw robust conclusions from these analyses. However, these data force us to question the impact of interventions focusing on exercise on energy balance.
Before resorting excessively to exercise to promote weight loss, it would be wise to ensure the real effects and repercussions of the intervention on energy balance. Conversely, to assert with certainty that in all cases exercise has no impact on weight loss would be just as risky. First, we must establish whether exercise contributes favorably to energy expenditure while being part of a process of negative energy balance.
Of course, it is essential to point out that the physical fitness of participants is not included in the analyses. It is possible that the fitness level between groups is different, which is an important factor for health. These analyses still require some data cleaning…
What should we remember? Let’s stop getting tangled up in the terms exercise and physical activity. It is advisable to adopt the WHO’s proposed definition and strive to use it daily. Exercise, yes, is physical activity. But physical activity is not just exercise. When it comes to weight management, it is crucial not to confuse exercise and physical activity. It is important to determine the impact of our intervention on energy balance. Exercising is unlikely to make you lose weight. Not because muscle increases more than a bodybuilder pumped with anabolic steroids. Let’s stop telling people that because they do strength training, they will gain a lot of muscle and the scale won’t go down. You don’t gain that much muscle that easily. Exercising is for improving your physical fitness, to become better. It contributes to our physical and mental health. It may be disappointing for many people if the only goal associated with exercise is weight loss. You will not systematically move more if you exercise. You will not systematically burn a lot more calories if you exercise. Stop saying that weight management is not a matter of energy balance. In the end, changes in weight and body composition are the result of a change in energy balance. Weight management is not about counting calories consumed and calories expended. Why? Because we are, even today, extremely imprecise at doing that. Your real energy balance that dictates your weight, we are not able to determine it precisely. That’s why trying to count everything is not really useful for determining if you are consuming more or fewer calories than you expend. But, if you gain muscle mass or fat mass, you must have been exposed to an energy surplus. If you lose it, you must have been exposed to an energy deficit. Now, where there is a lot of variability is in what influences this energy balance. What makes you ingest the calories you ingest and expend the calories you expend, that, that is very variable from one person to another and even from one day to another.
Exercising nowadays is beneficial for the vast majority of us. But it may not appeal to everyone. Doing physical activity is extremely beneficial for all of us. But, if it improves our health, it does not necessarily improve our physical fitness. Also, if we want to fully benefit from the advantages of physical activity, it helps to be fit.
In short, exercising to improve our physical fitness and increasing our level of physical activity with pleasure is an excellent combination. Exercising to lose weight is not as simple as pushing yourself and getting sweaty.
References:
Caspersen CJ, Powell KE, Christenson GM. Physical activity, exercise, and physical fitness: definitions and distinctions for health-related research. Public Health Rep. 1985;100 (2):126-131.
Garrow J, Summerbell C. Meta-analysis: effect of exercise, with or without dieting, on the body composition of overweight subjects. European journal of clinical nutrition. 1995;49(1):1-10.
Verheggen RJHM, Maessen MFH, Green DJ, et al. A systematic review and meta‐analysis on the effects of exercise training versus hypocaloric diet: distinct effects on body weight and visceral adipose tissue. Obesity Reviews. 2016;17(8):664-690.