Does Exercise Really Help With Weight Loss? If So, Why Do Experts Say It’s Useless?

I was shocked when I saw these tweets in my feed:

“Exercise is useless for weight loss. But at least it’s good for cardio fitness and health.”

“Exercise is negligible when it comes to fat loss. It’s heartbreaking to see people doing endless cardio with no results.”

Why was I shocked?” Because both tweets came from fitness coaches (“influencers”) with large followings – people I assumed were evidence-based. They should have known these statements were wrong, or at least half-truths being presented as absolutes.

Instant unfollow from me.

I don’t want to hear doom-and-gloom claims about how nothing works.

In random scrolling, I also came across two more alarmist tweets:

“Exercise is great for health, worthless for fat loss.”

“Exercise is good for you in many ways, just not for weight loss.”

These two were even more shocking because they were written by medical doctors. They were also wrong.

Not even an M.D. behind someone’s name guarantees you’re getting the full picture. MDs are not necessarily fat loss experts, and appealing to authority is not the same thing as understanding the science.

Maybe I shouldn’t have been so surprised and taken aback…

I’ve been hearing versions of “exercise doesn’t work for fat loss” since at least 2009, when Time magazine ran its infamous “Exercise Won’t Make You Thin” piece – an article I publicly dismantled here on the blog back then. It got thousands of views, hundreds of comments and is still read to this day.

But it’s time for an update.

What’s different now is scale. Social media has taken a half-truth, stripped it of nuance, and turned it into a viral narrative – fueled by new research that’s been widely misinterpreted.

Why Some Experts Say Exercise Doesn’t Help With Weight Loss

If this idea – “exercise doesn’t work for weight loss” – sounds familiar, there’s a good reason.

Over the past year, it’s been pushed back into the spotlight by a new wave of interviews, podcasts, and social media clips – often quoting respected researchers or “evidence-based” educators. In some cases, those quotes even show up on academic sites (Universities, etc), which gives the message extra credibility.

The simplified takeaway usually sounds something like this:

“Exercise doesn’t lead to fat loss because the body compensates.”

From there, this message gets repeated. And repeated. And repeated again.

Trainers hear it from mentors they respect. Influencers hear it from trainers. And before long, it’s being stated as fact – often without anyone stopping to question it or dig into just how nuanced this topic is.

The result isn’t clarity – it’s confusion – which I am clearing up ONCE AND FOR ALL in this Burn the Fat Blog post.

The Core Idea Behind the Claim

The argument usually traces back to a concept called “constrained energy expenditure.”

Some science-savvy readers will recognize that term. Many won’t. Either way, here’s the simple version:

When you increase exercise, your body adapts. Just like your metabolism can slow down when you cut calories, it can also adjust when you increase physical activity.

Over time, your body may conserve energy elsewhere – through subtle changes in movement, hormones, or efficiency – so your total calorie burn isn’t as high as you thought it would be (or as high that cardio machine readout told you, lol).

That part is real. That part is supported by research. Where things go off the rails is what happens next.

Where The Exercise And Weight Loss Message Gets Oversimplified

Instead of saying:

“Exercise causes metabolic adaptation, which can reduce the expected calorie burn over time,” the message gets flattened into: “Exercise doesn’t work for weight loss.”

Do you see the problem?  That leap strips away:

• Time frames
• Training type
• Formal exercise dose
• Non exercise activity (NEAT)
• Diet context
• Individual differences

And it turns a nuanced physiological insight into a blanket conclusion. That’s how a useful scientific concept becomes a misleading soundbite repeated on social media.

Why This Spreads So Easily

This message spreads fast because it feels validating: It explains why fat loss is hard. It removes blame. And it sounds smart.

But when it’s delivered without nuance, it leaves people wondering: “Should I even bother exercising? Is all this effort pointless? If cardio “doesn’t work,” what am I supposed to do instead?”

Those are reasonable questions – and they deserve real answers, not sound bytes – which I am here to give you. It’s my job.

The Research Behind The “Constrained Energy” Argument

There’s an increasingly popular idea that your energy expenditure is “constrained.” It’s also widely believed that you “compensate” for calories you burn.

In simple terms, this means that when you exercise more, some of the extra calories you burn get canceled out somewhere else.

To examine this hypothesis, a review of studies using the highly accurate doubly labeled water method was published in the scientific journal Clinical Biology (Careau, Pontzer et al).

The main finding was that in normal, moderately active people, energy compensation did happen. The average amount was about 28%, which researchers assumed came from a drop in basal metabolic rate.

In practical terms, this is like saying that for every 100 calories you burned through exercise, only 72 of them “counted.”

That would kind of suck – if that were the whole story.

But even if this finding is accurate, it’s not total compensation. The study didn’t say that exercise doesn’t help with weight loss. It showed that increases in your total daily energy expenditure from exercise are not perfectly linear, and therefore may produce less fat loss than you expect – not zero fat loss!

What The “Energy Compensation” Study Really Showed Vs How It Was Reported

When these results were published, the internet blew up with videos, podcasts, articles, Instagram posts, and tweets – including examples like the ones I shared above.

The problem is that many people read the commentary and treated the results of this single study as if it were definitive proof.

In summary, the takeaway from that study was:

“A portion of the calories you burn from exercise don’t count, because fewer calories are burned somewhere else in the body to compensate.”

That interpretation may or may not be true, depending on the person, the type of exercise, and the context –  but it’s already an over-simplification.

Then it got distorted even further. People blew the results completely out of proportion by claiming:

“Exercise is useless for weight loss!”

That conclusion is absolutely false. It’s a straight up lie.. or ignorance…  one or the other.

The study did not show that exercise is useless for fat loss. It showed that some compensation can occur. that means the relationship between exercise and total daily energy expenditure is more complex than a simple calories-in, calories-out equation.

Simply stated: The calorie math equation can change!

When you dig deeper into the science, it also becomes clear that this study had limitations – including the fact that it was observational, which means it can’t establish cause and effect.

What Higher Quality Studies Show About Exercise And Metabolic Rate

Most studies that can establish cause and effect – specifically randomized controlled trials – find that the effect of exercise on basal metabolic rate (BMR) is either neutral or slightly positive.

This is especially true for resistance training, which helps preserve or increase muscle mass – a key driver of resting metabolism.

In 2020, a meta-analysis by MacKenzie‑Shalders and colleagues reviewed 22 studies, most of them randomized controlled trials, to examine the effect of exercise on BMR.

Here’s what they found:

• Aerobic training had no significant effect on BMR
• Resistance training increased BMR compared to control groups
• Combined aerobic + resistance training also showed no decrease in BMR

In other words, exercise did NOT lower metabolic rate.

When aerobic exercise alone was performed, BMR neither increased nor decreased, meaning there was no evidence of metabolic “compensation” at rest. When resistance training was included, BMR actually increased.

Resistance training doesn’t burn as many calories per session as steady-state cardio. But it does burn calories, and more importantly, it plays a critical role in preserving muscle and preventing metabolic slowdown, especially during fat loss.

Why Exercise Sometimes Doesn’t Lead To Weight Loss

There is evidence that some kind of compensation really does happen when you increase your exercise level. We know this because in many weight loss exercise studies, the actual amount of weight lost doesn’t match what you’d predict based on the amount of exercise done.

The question is why? Why are the fat loss results that most people get from cardio less then they expected?

There are four plausible explanations.

1. Metabolic adaptation (BMR changes)

Increasing exercise could eventually lead to a decrease in basal metabolic rate, similar to what happens when calories are cut aggressively.

This is the hypothesis behind the “constrained energy” argument, but as you’ve already seen, higher-quality studies suggest this effect is limited, not universal or absolute.

2. Reduced non-exercise activity (NEAT)

Increasing exercise can also lead to a drop in non-exercise activity later in the day. I discussed this in my last post on this subject (why cardio doesn’t work, even if you’re doing a lot of it).

You crush a hard workout in the morning, but then you subconsciously move less the rest of the day – or just flat out crash on the couch because you’re exhausted.

This has been documented most clearly after very intense training, and it tends to be more pronounced in older individuals.

3. A smaller body burns fewer calories

When exercise (and/or dieting) leads to weight loss, you now have a smaller body. And here’s the golden rule you must always remember: Bigger bodies burn more calories. Smaller bodies burn fewer calories.

That means the calorie math you started with is no longer accurate. Even if nothing “went wrong,” your original calorie prediction simply doesn’t apply anymore.

Differently stated: A calorie deficit is a moving target.

4. Increased food intake

Finally, increasing exercise often leads to increased hunger and food intake.

Sometimes this is obvious. Sometimes it’s subtle. Either way, eating back the calories you burned will obviously cancel out some (or all) of your fat loss.

I wrote about this in a previous post as well:  You can’t out-run a bad diet

Your Metabolism May Adapt To Exercise – But Not Enough To Stop Weight Loss

We know that when you cut calories and create a deficit, your body can adapt and slightly reduce metabolic rate – a phenomenon often called metabolic adaptation.

Ever hear about how the Biggest Loser contestants wrecked their metabolisms from insane dieting and exercising?  That’s the most dramatic example. (The True Cost Of The Biggest Loser – Burn The Fat Blog).

But under normal circumstances, the metabolism adaptation is small – not  nearly enough to stop weight loss. But it is enough that the actual amount of weight lost ends up being less than what you’d predict on paper.

This is also one major reason your weight loss starts to slow down automatically after months of dieting (sound familiar?)

Since metabolism can slow slightly from dieting (cutting calories), it’s not unreasonable to ask whether the opposite could also happen – whether metabolism might slow in response to exercise (burning calories).

The human body is highly adaptive. But contrary to this popular anti-exercise narrative spreading around the internet lately, it’s crash dieting that’s the bigger concern.

Severe Calorie Cutting Is A Bigger Worry Than Adding Exercise

In a 2012 study by Byrne, obese men and women followed a very low-calorie diet combined with exercise.

The protocol included:

• 500–600 calories per day
• 4 days per week of walking
• 2 days per week of resistance training
• Based on calorie math alone, the participants should have lost more weight. Instead, they lost about 33% less than predicted.

If dietary compliance was high – and there’s good reason to believe it was – then some degree of metabolic adaptation or compensation clearly occurred.

But notice where the stressor was:

The diet was extreme.
The exercise was not.

It’s almost certain that most – if not all – of the adaptation came from the severe calorie restriction, not the exercise. And yet, despite that adaptation, participants still lost a large amount of weight: About 18 kg in men and about 15 kg in women in just 12 weeks.

Metabolic adaptation did not prevent weight loss. It simply reduced the amount lost compared to a theoretical prediction on paper.

Exercise Does Work For Weight Loss – You Simply May Be Burning Less Than You Thought

Here’s the bottom line.

There is metabolic adaptation to dieting. There may be some metabolic adaptation to exercise. But neither one stops weight loss.

Exercise still works for fat loss – it simply  may not burn as much as a basic calorie calculator predicts.

It’s possible that future research could show that very high levels of sustained energy expenditure lead to some degree of compensation or reduced metabolic activity elsewhere in the body. That idea isn’t absurd.

The problem is that this possibility keeps getting stretched into a conclusion it doesn’t support.

The real questions aren’t whether compensation can happen – they’re when, to whom, and under what conditions.

Who Is Most Likely To Experience Energy Compensation?

The constrained energy model was originally proposed by evolutionary anthropologist Herman Pontzer based on research in hunter-gatherer populations, including the Hadza of Tanzania.

In that context, energy constraint isn’t hard to imagine. Hunter-gatherers are extremely active, often energy-limited, and shaped by generations of evolutionary pressure

It’s also plausible that we might see similar compensation in high-volume athletes who train hard but fail to eat enough.

In both cases, you’re looking at energy insufficiency – very high expenditure paired with inadequate intake.

That’s a different physiological situation than what most people mean when they talk about “exercise for weight loss.”

When calorie intake is extremely low, metabolic adaptation is well documented. If very high energy expenditure is combined with under-fueling, that would be a double hit. But those situations are edge cases, not the norm.

For the average sedentary person in modern society – someone increasing activity from 4,000 steps a day to 8,000 or 10,000, doing two or three sessions of formal cardio, adding a few days a week of resistance training, and eating a reasonable calorie deficit – there’s no evidence that exercise gets “canceled out” by a drop in BMR.

What we typically see instead is improved body composition, better metabolic health, and better long-term weight control.

Even people going from moderately active to highly active don’t appear to experience exercise being neutralized – as long as they lift weights and don’t starve themselves.

The #1 Reason Exercise Doesn’t Appear To Work: Eating Back The Calories

Across all the research, the most consistent explanation for “compensation” is not a slowing metabolism – it’s eating more.

In fact, studies suggest that explanations #2, #3, and #4 from my list above account for most of the gap between expected and actual weight loss – with increased food intake being the biggest factor.

In a 6-month randomized controlled trial published in 2019, participants who exercised lost less weight than predicted.

But it wasn’t because their metabolism slowed, it was because they ate their freaking calories back!  That doesn’t mean exercise doesn’t work, it means they made a diet mistake!

That’s why a study showing ~28% compensation to exercise to exercise shouldn’t panic you. The real danger isn’t metabolic shutdown – it’s quietly wiping out your deficit with extra food (that you thought you “earned”).

If you reward yourself with food every time you exercise, it’s possible to compensate 100% or more of the calories you burned.

For some people – especially shorter, petite women – one unplanned muffin can erase an entire day’s exercise deficit. And that’s exactly why the old cliché still holds:

You can’t out-train a bad diet.

Does Exercise Increase Appetite – And Does That Mean Exercise Doesn’t Work?

At this point, some people might object: “But Tom, if exercise increases appetite, isn’t that still a problem?” Not necessarily.

First, it’s a myth that exercise always increases hunger. In fact, much of the research shows that people who exercise regularly have better appetite regulation, meaning calorie intake tracks more closely with calorie expenditure over time.

Whether exercise increases hunger depends on many factors:

• Exercise type and intensity
• Total volume
• Genetics and individual response
• Size of the calorie deficit
• Fed or fasted exercise
• How lean someone already is

Many people report reduced appetite after intense exercise, especially interval training or lifting weights. Others find that simply going for a walk reduces cravings.

On the flip side, some forms of exercise – such as long-distance running or swimming in cold water – may increase appetite in certain people.

Yes, hunger can increase when you’re in a calorie deficit. That’s normal. But in many cases, the tendency to eat more after exercise is behavioral rather than biological — a reward response, not true physiological hunger.

And that distinction matters.

Exercise Helps You Lose Weight, But More Is Not Always Better

Exercise absolutely helps with weight loss. The limitation isn’t metabolic shutdown – it’s failing to understand that you might cancel out the fat loss benefits of exercise by eating more or moving less the rest of the day.

Also, exercise-only weight loss studies show disappointing results simply because the exercise dose is too small. Thirty minutes of cardio a few days a week doesn’t create a large calorie deficit for most people. Do the math and you’re often looking at about a pound per month – sometimes less.

Three days a week of cardio is nothing – what did you expect?

And there’s another detail most people miss: cardio machines overestimate calories burned. The number you see includes calories you would have burned anyway just by being alive. The net calories burned from the exercise itself are usually lower than advertised.

None of this is meant to discourage exercise – it’s about setting realistic expectations.

If you increase exercise gradually, you’ll usually find a sustainable sweet spot where fat loss improves beyond diet alone. But as exercise volume climbs higher, returns diminish. Time becomes limited. Fatigue increases. NEAT can drop. Lifting performance can suffer.

At some point, very high volumes of exercise become impractical for anyone with a normal life.

Ironically, the people most capable of sustaining huge amounts of cardio are already lean athletes – and they usually don’t need to lose fat.

For many people, the same calorie deficit could be created more easily by eating slightly less – skipping half a sandwich, choosing water instead of soda, or passing on the chips.

That said, if calories are already low, cutting food further may not be smart, and exercise becomes the best way to increase the deficit.

The Take Home Message About Exercise For Weight Loss

Exercise does help with weight loss.

But diet is the most efficient way to create a calorie deficit when you have room to adjust it.

That’s the message fitness, health, and medical professionals should be sharing – not the nonsense tweets that say “exercise doesn’t work for weight loss.”

The most reliable approach is simple:

• Control diet (calories) first priority
• Add a sustainable amount of cardio you enjoy
• Always include resistance training to preserve muscle and metabolism

Do that, and fat loss improves every time.

And finally – even if weight loss weren’t a factor at all – exercise would still be worth doing.

It improves metabolic health, mental health, longevity, and quality of life in ways no diet ever could. That alone is reason enough to keep moving.

Tom Venuto
Author, Burn the Fat, Feed the Muscle
Author, Flexible Meal Planning For Fat Loss
Founder, Burn the Fat Inner Circle

PS. If this resonates with you, please feel free to share.

PPS. What has YOUR experience been like using increased exercise for fat loss? Scroll down and post in the blog comments below.

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About Tom Venuto, The No-BS Fat Loss Coach
Tom Venuto is a natural bodybuilding and fat loss expert. He is a former competitive bodybuilder and today works as a full-time fitness coach, writer, blogger, and author. In his spare time, he is an avid outdoor enthusiast and backpacker. His book, Burn The Fat, Feed The Muscle is an international bestseller, first as an ebook and now as a hardcover and audiobook. The Body Fat Solution, Tom’s book about emotional eating and long-term weight maintenance, was an Oprah Magazine and Men’s Fitness Magazine pick. Tom is also the founder of Burn The Fat Inner Circle – a fitness support community with over 52,000 members worldwide since 2006. Click here for membership details

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Scientific References

Byrne NM et al, Does metabolic compensation explain the majority of less-than-expected weight loss in obese adults during a short-term severe diet and exercise intervention?, International Journal of Obesity, 36, 1472–1478, 2012

Careau V, Pontzer H, et al, Energy compensation and adiposity in humans, Current Biology, 31, pp1-8, October 2021.

MacKenzie-Shalders, et al, The effect of exercise interventions on resting metabolic rate: A systematic review and meta-analysis, Journal of Sports Science,38(14):1635-1649, 2020.

Martin C et al, Effect of different doses of supervised exercise on food intake, metabolism, and non-exercise physical activity: The E-MECHANIC randomized controlled trial, American Journal of Clinical Nutrition, 110(3):583-592, 2019.

Ross R and Janssen I, Physical activity, total and regional obesity: dose-response considerations. Med. Sci. Sports Exerc., Vol.33, No. 6, Suppl., S521–S527, 2001.

Thomas, DM et al, Why do individuals not lose more weight from an exercise intervention at a defined dose? An energy balance analysis, Obes Rev. 13(10): 835–847. 2012

Thomas D, Heymsfield S, Exercise: Is More Always Better? Current Biology Dispatches, R102–R124, 2016.

Related Articles About Whether Exercise Helps With Weight Loss:

The Latest Science On Metabolic Adaptation: What It Is And What You Can Do About It

Exercise Won’t Make You Thin? (Why Time Magazine Owes The Fitness Industry A Big Fat Apology)

Why Cardio Doesn’t Work (Even If You’re Doing A Lot Of It): A NEAT Explanation

You Can’t Out-Train A Bad Diet