If you don’t use it, you’ll lose it. Wait—maybe you’ll gain it? When it comes to our bodies, we’ve all heard the advice that in order to lose weight, we need to eat less and exercise more (you know, calories-in, calories out). However, after reading Gary Taubes’ book Why We Get Fat: and what to do about it, I’ve learned that modern public health officials got it wrong. Why do we lose more weight when not exercising?
First and foremost, research shows that physical activity is good for us. Lifelong physical activity reduces the risk of many cancers, prevents insulin resistance and Type II Diabetes, and is great for our tendons and joints1.
However, what the research does not conclusively show is that exercise helps us to lose weight. As the authors of this 2018 review put it, “proving a causative relationship between exercise and weight loss maintenance is difficult at present”2.
In Why We Get Fat, Gary Taubes has us consider the things we would do before going to a celebratory dinner in order to be hungry for the food that will be served (Taubes, 2011, p. 40). Most of us would eat light beforehand, maybe skip lunch. Some of us would probably “go to the gym for a particularly vigorous workout…to work up an appetite”. Taubes’ goes on to highlight the irony in this…
Now let’s think about this for a moment. The instructions that we’re constantly being given to lose weight—eat less…and exercise more…—are the very same things we’ll do if our purpose is to make ourselves hungry, to build up an appetite, to eat more (Taubes, 2011, p. 40).
Americans used to be thin, but they exercised less than we do today
We’re a pro-exercise nation. For lots of folks, it’s routine to wake up and go for a three-mile run. Some can’t function without pumping iron at the gym after work. Still others prefer to get an at-home sweat session by doing a 20-minute HIIT workout. Despite all this, Americans are heavier than ever—today, we weigh about 30 pounds more than the average person did in the 1960s3.
In the 60s and 70s up to the 80s, people were less intentional with their physical activity than we are today. (check out the rise of fitness centers since their establishment in America in the early 70s). Back in the day, people simply lived their lives and yet were still fairly slim, at least compared with today’s standards.
Why do I Lose More Weight when Not Exercising?
Exercise is a type of intentional physical activity, which all falls under the umbrella term “energy expenditure”. Energy expenditure is the amount of energy (calories) that the cells of our bodies use (burn) to function. Some energy (calories) is sent to our adipocytes (fat cells) to be held temporarily for future energy, while other energy (calories) is sent to our muscle cells to be used (burned) as fuel for more immediate use. Generally speaking, we want our fat cells to be good at temporarily capturing energy, not storing it forever. And, we want our muscle cells to be good at capturing calories and burning them for energy. (This is what is meant by having a “fast metabolism”).
Yes, working out (expending energy), causes our muscle cells to burn lots of calories. But still, as in the case of the aforementioned celebratory dinner party, you will work up an appetite if you expend more energy. This is because there is a loose coupling of energy expenditure and energy intake—the more we expend, the more we intake; the less we expend, the less we intake4. This may be why, for example, there is weak evidence that workplace sedentary time interventions are effective at helping office workers lose weight5. There is no guarantee that the calories expended from their physical activity were not overcompensated by their consumption of a greater number of calories to replace those lost.
One study found that 50% of their participants were “compensators” because they consumed more food after they exercised compared to when they did no exercise6 (the other half were not compensators as there was no change in intake regardless of whether or not they exercised). This is in line with a conclusion of a review on much of the research on this topic that “Energy intake of humans is usually increased or unchanged in response to exercise training programmes”7. Specifically, the authors note, lean and athletic people tend to increase energy intake with exercise, while obese and non-athletic people tend to have no changes in energy intake with exercise. This may explain, in part, why many overweight people lose weight at the very beginning of their exercise journey, but after a while they reach a plateau—in the beginning, they are burning more calories than they are consuming, but after they lose a little weight, because their eating has not changed, they are no longer in a negative energy balance.
Importantly, there is evidence that in the long term, people reach for carbohydrates after working out8,9. These carbohydrates, especially the refined kinds, can cause a rush of insulin. This is the hormone that encourages our adipocytes (fat cells) to store fat.
Even if you are a non-compensator (you don’t eat more food after exercising), the way your body expends energy will change to keep you at a balanced state of energy. A group of researchers explain that “a long-term increase in activity does not directly translate into an increase in total energy expenditure because other components of [total energy expenditure] may decrease in response10“. Because exercise is just one aspect of total energy expenditure, the other aspects (non-exercise activities) of energy expenditure may reduce themselves in such a way to reach a balance between total energy expenditure and energy intake. Even the strictest dieters will not lose more weight from exercise alone.
There you have it, you lose more weight when not exercising because of the coupling between energy expenditure and energy intake—when we expend more energy, we usually: 1) increase energy intake in the form of fat-storing carbohydrates and 2) reduce energy expenditure in n0n-exercise activities
- https://pmc.ncbi.nlm.nih.gov/articles/PMC6027933/ ↩︎
- https://www.metabolismjournal.com/article/S0026-0495(18)30227-0/abstract ↩︎
- https://www.washingtonpost.com/news/wonk/wp/2015/06/12/look-at-how-much-weight-weve-gained-since-the-1960s/ ↩︎
- https://onlinelibrary.wiley.com/doi/10.1038/oby.2007.164#b35 ↩︎
- https://pmc.ncbi.nlm.nih.gov/articles/PMC6437332/ ↩︎
- https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0282501 ↩︎
- https://link.springer.com/article/10.2165/00007256-198806030-00002 ↩︎
- https://www.sciencedirect.com/science/article/abs/pii/S0031938497003533?via%3Dihub ↩︎
- https://journals.lww.com/acsm-msse/fulltext/1997/08000/effects_of_exercise_on_appetite_control_.14.aspx ↩︎
- https://pmc.ncbi.nlm.nih.gov/articles/PMC8551017/ ↩︎