Does exercise help you lose weight? Of course it does… right? Well, maybe not. As the research piles up on exercise and its true contributions to weight loss, it turns out that while exercise has astounding benefits for health, it may not actually move us closer toward our weight loss goals – and too much exercise could in fact sabotage our goals altogether. Let’s delve into the research and find out more.
Burning more calories than we consume (or the “move more, eat less” philosophy) is the gold standard for weight loss. Yet, studies show that this formula doesn’t always work.
Exercise contributes only a small amount to our overall daily calorie expenditure, making it challenging to create a meaningful calorie deficit for weight loss. There are three components that contribute to energy expenditure: 1) Food digestion, 2) Basal metabolic rate (BMR), or the set amount of baseline calories your body needs to carry out its daily functions, and 3) Exercise (this includes any physical movement beyond a resting state). Food digestion contributes approximately 10% to your daily calorie expenditure, BMR 60 to 80%, and exercise accounts for 10 to 30%. Because exercise contributes such a small amount to how many calories we burn on a daily basis, it’s very challenging to add a significant amount of calorie deficit through exercise.
Have you ever worked out hard at the gym, then sat down to eat, only to realize you consumed more calories in the first 5 minutes of your meal than you just burned during your entire workout? A 3500-calorie deficit is technically equal to 1 pound lost. This means burning 500 calories (as much as 1 hour of cardio) through exercise each day for 7 days, without consuming more food to make up for the calories burned. In other words, this is a lot of exercise with very little return.
Exercise sometimes results in more calories consumed and less calories burned. Exercise has been shown to increase appetite, hunger levels and hormones associated with hunger, making it difficult for most people to not eat more when participating in an exercise program. In addition, studies show that when people exercise, they mentally log the calories burned and reward themselves, often eating more than they would if they hadn’t exercised.
Exercise can also result in fewer calories burned throughout the rest of your day. If you exercise hard in the morning, you might be less likely to take the stairs, pace while on the phone, walk to the store, or fidget while working at your desk – all of which contribute to your daily calorie expenditure.
Recent and surprising scientific findings about our bodies may prevent us from expending too many calories through exercise. A 2012 study compared calorie expenditure between the Hadza, one of the last hunter-gatherer communities in Tanzania on the high end of the activity spectrum, and Westerners in the U.S. and Europe who spend most of their days on the low end of the activity spectrum. Results were astonishing showing that the two groups burned approximately the same amount of daily calories. While the study was small and participant pool unvaried, research points to some meaningful explanations about how this could be possible.
First, energy expenditure may be more fixed than previously thought. Research shows that there is most likely an upper limit as to how many calories we burn, and once this upper limit is reached, calorie expenditure plateaus.
Second, a scientific finding called “metabolic compensation” states that when we stress our bodies with physical exercise past a certain point, physiological changes kick in to preserve calories. Studies have shown that intense exercise could cause a lowering in our BMR as a type of “survival mechanism”, preserving fat stores for later use, and this BMR lowering can be lasting. Metabolic compensation could also be explained simply by the fact that when we intensely exercise, we preserve energy through the remainder of the day by moving (and fidgeting) less. While scientists are still figuring out the specifics regarding metabolic compensation, it is a well-documented phenomenon.
But doesn’t exercise increase your muscle mass and in turn your resting metabolic rate (RMR), which increases the amount of calories you burn throughout the day? Well, not exactly. It’s estimated that 1 pound of muscle burns approximately 7 to 10 calories per day at rest, while 1 pound of fat burns 2 to 3 calories per day. Replacing a pound of fat with a pound of muscle would therefore result in burning 4 to 6 more calories per day. When you think about the fact that on average, a 4-month strength-training program adds 3 to 5 pounds of muscle mass, you’re looking at burning no more than 30 extra calories per day. While some studies show a moderate increase in RMR in some individuals who strength train over long periods of time, these increases are not significant enough to induce meaningful weight loss. And remember, with an increase in RMR comes increased calorie needs, hunger, and most likely an increase in calorie intake.
For all of these reasons, exercise alone is of minimal value when it comes to losing weight. So why exercise? Well, the benefits of exercise are so incredible, that while exercise may not decrease the number on your scale, it will exponentially increase your protection against disease, your quality of life, your mental health, your lifespan, and just about every health marker that exists, even if you never lose a pound. Exercise is one of the keys to a healthy life, and while it’s difficult to remember this in a society that values weight loss above health, there’s more to life than the number on your scale.
At Gutbliss, we recommend exercising daily and especially outdoors for better health. And for those trying to lose weight, focusing on what you eat (check out Dr. Chutkan’s Veleo Diet, which is geared toward optimizing microbial health) is THE BEST place to start.
Why weight loss is all about the food
Lastly, and maybe most importantly, in the end, your caloric intake and expenditure doesn’t really matter; the kind of food you consume matters much more.
Take 500 calories of packaged chocolate chip cookies versus 500 calories of Brussels sprouts. After consuming the cookies your body is thrown into a biological cascade of spiked blood sugar, elevated inflammation, a rise in triglyceride levels, leptin resistance (feeling of fullness hormone), an increased addiction to sugar, and a rise in pathogenic gut bacteria. All of these biological changes increase hunger cravings, calorie extraction from food, and body fat storage, and decrease your nutritional status and microbial health – all factors that result in weight gain.
When consuming 500 calories of Brussels sprouts, your body reacts quite the opposite – blood sugar levels are regulated, inflammation reduced, good cholesterol and leptin levels increased, and beneficial gut bacteria multiplied. And in fact, while the Brussels sprouts contained 500 calories, only a portion of these calories are actually extracted and stored by the body – the rest are bound by fiber and travel to your colon to feed gut bacteria. These positive biological changes that occur when consuming a high fiber, whole food like Brussels sprouts create an environment that promotes appetite control, decreased body fat storage, and a healthy weight.
As is evident from the above description, processed, high fat, high sugar foods like chocolate chip cookies (and processed foods in general, even those geared toward weight loss), throw your inner biological machine out of whack, making weight management a never-ending struggle; while a diet comprised of 100% fibrous, whole foods optimizes your biological machine, making weight something your body naturally moderates, without you ever needing to work at it.
Let’s consider the Hadza. They burned the same amount of calories as sedentary Westerners, yet they possess a very lean body type. This is because the food they eat – like the Brussels sprouts – leads to better appetite control, decreased body fat storage, and a healthy weight.
You may wonder what role the gut microbiome plays in all of this. Not surprisingly, studies show that exercise positively alters your gut microbiome. Research also points to the idea that a disordered microbiome, specifically one higher in Firmicutes and lower in Bacteroidetes, can result in an increase in energy harvesting (more calories extracted from the food). So it makes sense that using exercise as a tool (one of many) to balance the gut microbiome could result in a healthier microbial profile that extracts fewer calories from food. Yet, no direct scientific evidence exists to quantify how positive microbial shifts through exercise affect calorie extraction, expenditure, and weight loss. This may be something we will see in the scientific literature in the future. But keep in mind, if you want to test this philosophy, the number one way to promote a balanced microbiome is through the food you eat.
Bottom line: Exercise daily for health, eat for health, and if you’re trying to lose weight, focus on the types of food you’re consuming, not the number of calories you take in and burn.