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Exercise is one of the best things you can do for your health, but it’s not a reliable weight-loss tool. Most people burn fewer calories than they think, and the body often compensates with increased hunger and reduced movement later in the day. If weight loss is the goal, diet changes tend to move the needle far more than workouts do. The win is still massive, though: exercise improves mood, metabolism, strength, longevity, and disease risk in ways food alone can’t replace.
Exercise is good for you. Extremely good for you. In fact, it’s now occurring to our best experts that we’ve been drastically underestimating how important activities like cardio and strength training are for giving us longer, richer, happier lives. And it’s already been a cliche that if we could swallow a pill that does as much for our health as exercise, it would rightfully be the hottest-selling wonder-drug in human history. But despite all of its incredible benefits, there is one thing it simply isn’t good for: helping us lose weight.
The prevailing narrative of “eat less, move more” has been the cornerstone of weight loss advice for decades. The importance of the ‘move more’ component, in particular, has been fiercely championed by high-profile actors. Michelle Obama waged her ‘Let’s Move’ campaign to end childhood obesity, and Coca-Cola funded an entire non-profit organization called the to remind us that a couple extra sodas are no big deal as long as we keep active. Whether well-intentioned or (decidedly) not, the problem with this advice is that it sets people up for failure.
Countless studies affirm that exercise alone has minimal impact on weight loss:
An enormous systematic review and meta-analysis published in the Journal of American Medical Association in December 2024 looked at no less than 116 randomized clinical trials involving 6880 participants. This sweeping overview of all available high-quality research found that every 30 minutes of aerobic exercise per week was associated with a reduced body weight of about one pound. So, technically, exercise can help with weight loss. However, as the authors concluded, “...aerobic training exceeding 150 minutes per week at moderate intensity or greater may be needed to achieve clinically important reductions.” In other words, if you want to lose more than 5 pounds on an exercise program, you will have to really go for it on the treadmill for more than half an hour, five days a week.
An earlier review from October 2023 concurred with this consistently found observation: while exercise is associated with some weight loss, “.” It’s important to point out that findings like these can be (and are) used to make the point that exercise does, in fact, result in ‘significant’ weight loss. But that’s a deeply misleading presentation of the truth. If more people understood just how hard, consistently, and long-term they would have to work out for a measly 6 pounds of weight loss, they might, understandably, lose interest, patience, and motivation even sooner.
None of this is to say exercise isn’t invaluable. The health benefits of physical activity are so profound and far-reaching that they are literally beyond compare:
Exercise is one of the best things you can do for your health. It might even be the very best thing you can do for your health. It’s hard to overstate the ability of an enjoyable exercise routine to improve life in countless ways. But if weight loss is your goal, focusing on what you eat will yield far better results.
The “eat less, move more” mantra oversimplifies a complex problem. This can, and does, frequently mislead well-intentioned people who are then inclined to blame themselves for failure when the advice itself is at fault. Instead, let’s celebrate exercise for what it really is: a transformative game-changer for living a longer, happier, and radically healthier life- just not a much slimmer one.
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Even if we cling to the essentially debunked notion of ‘calories in, calories out’, exercise alone simply doesn’t burn enough calories to make a meaningful dent in body weight. For example, speed walking for half an hour burns roughly 140 calories, less than one can of Mountain Dew. Some would argue it’s easier not to drink the pop than try to walk it off.
In controlled trials where participants drastically increased their physical activity, weight loss was modest at best. In one study, 81 overweight women stuck to an intensive 12-week treadmill program. But instead of shedding pounds, many of them actually gained weight.
Why? Because, when you exercise, your body compensates in two primary ways. The first is by increasing appetite. As Gary Taubes relatably illustrates, if someone invited you to a deluxe dinner feast and told you to make absolutely sure to arrive ravenous, what would you do?
Chances are you’d go for a vigorous workout. The phrase ‘working up an appetite’ contains the same intuitive truth: exercise makes us hungry. We might decide to skip the Mountain Dew and go for a brisk walk around the block instead, but when we return home, we have a new and potentially irresistible desire to drink that soda after all.
The body’s second compensatory mechanism for maintaining energy balance works by decreasing non-exercise activities like fidgeting or standing. It’s not uncommon for people to get home from the gym and just lie down looking at their phones or watching TV. Taking it easy after you work hard, or work out, is another intuitive reality that’s all too relatable.
All in all, the body’s self-regulation and conservation of energy represent a sophisticated metabolic system honed by evolution to preserve energy and maintain homeostasis for survival. And as it turns out, physical movement is a pretty small part of this puzzle.
Exercise accounts for a surprisingly small portion of total daily energy expenditure. The vast majority (from 60 per cent to 80 per cent,) is burned at rest, fuelling essential functions like cell repair, immune system upkeep, digestion, and brain activity. Physical activity contributes only about 10 per cent to 30 per cent. Herman Pontzer’s landmark research on the Hadza hunter-gatherers in Tanzania brought this fact of physiology into stark relief. Somewhat astonishingly, Pontzer’s rigorous fieldwork and lab analysis unearthed the profound discovery that some of the most physically active people in the world burn scarcely more calories than sedentary Americans. Whether moving a lot or a little, our metabolism has evolved to constrain energy expenditure.
The energy balance equation breaks down further when we consider the body’s adaptability. Metabolism slows as we lose weight, as demonstrated by follow-up research on contestants from The Biggest Loser reality show. Despite intense exercise regimens, rigid caloric restriction, and drastic weight loss, participants saw their metabolism plummet by an average of 500 calories per day. This metabolic adaptation makes it nearly impossible to sustain significant weight loss through exercise alone. This speaks, once more, to an evolved set of regulatory systems our bodies are equipped with that stop us from burning too many calories or losing too much weight.
A 2017 controlled trial compared a group that restricted carbohydrates but did not exercise with a group that ate normally but exercised consistently. After 10 weeks, it was abundantly clear that the carbohydrate-restricted group outperformed the exercise group in terms of weight loss, blood sugar balance, and body fat percentage. It might not be intuitive that eating differently- even without a specific focus on caloric restriction- can be more effective than exercise for losing weight. But that’s exactly what the study found. In fact, multiple meta-analyses have confirmed that while exercise alone isn’t an effective way to lose weight, eating differently really can be.
It reduces the risk, or delays the onset, of over 40 specific chronic diseases, including diabetes, osteoporosis, cancer, heart disease, non-alcoholic fatty liver disease, arthritis and stroke.
Regular exercise improves cognitive function and mental health. One narrative review described the evidence of exercise’s ability to reducing symptoms of stress, depression, and anxiety, as “irrefutable,” which is uncharacteristically strong language for scientific literature, to put it mildly.
A large 2023 review in the Journal of Sport and Health Science outlined in detail the mechanisms whereby exercise improves gut microbiome diversity, immune function, cardiovascular fitness, leaky gut, the strength of the blood-brain barrier, overall metabolism and more.
A gargantuan meta-analysis of 150 Cochrane systematic reviews concluded exercise reduces mortality and improves quality of life “with minimal or no safety concerns.” In other words, there is only profound, life-changing benefit and essentially zero downside to doing it.
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Lead image by Victor Freitas on Unsplash.
