I avoided cardio for the first decade of my training. I told myself it was for people who didn’t know how to lift, that it killed your gains, that walking was for retirees. Most of what I told myself was a coping mechanism for not wanting to do the work. I was wrong on every count, and the version of me who eventually started doing some cardio at 35 found out that almost nothing about it is what gym culture said it was.
If you’ve come to this article because you’re trying to lose weight and you keep getting told you have to do HIIT five days a week or it doesn’t count, this is the version that pushes back on that.
What I Got Wrong About Cardio
For years I believed three things that turned out to be either wrong or much smaller than the marketing said.
The first was that cardio was for people who weren’t serious about training. That belief was mostly a brand identity. The second was that the only cardio worth doing was the hardest kind. The third was that walking didn’t count.
The actual research is more boring than any of those positions. What it consistently shows is that the kind of cardio you do matters much less than whether you do it at all. The total time and total energy moved across a week matters more than whether you got there through sprints, an elliptical, or a long walk.
HIIT Versus Steady-State (The Boring Tie)
The argument the fitness internet loves is HIIT (high-intensity interval training) versus MICT (moderate-intensity continuous training, the boring jog). HIIT looks better in marketing. It promises more results in less time. The actual research doesn’t support most of those claims.
A 2017 meta-analysis in Obesity Reviews pooled 13 studies comparing HIIT to MICT in adults with overweight or obesity and found that the two produced similar reductions in body fat and similar reductions in waist circumference. HIIT was time-efficient and worked well for people who could tolerate it. MICT was easier on joints, easier on motivation, and produced the same body composition results when total work was comparable.
That’s the headline finding. Pick the kind of cardio you’ll actually do. The studies aren’t telling you HIIT is special. They’re telling you it’s the same as the boring version in terms of fat loss, which is the only thing that matters if your goal is weight loss.
What Actually Drives Fat Loss From Cardio
Cardio contributes to fat loss in three ways that are real and one way that is mostly a myth.
The real ones: it burns calories during the session, it raises total daily energy expenditure modestly over time, and it makes you better at recovering from training. None of these are dramatic individually. They add up.
The myth is that cardio cranks up your metabolism for hours after you’re done. The “afterburn effect,” or EPOC, exists but is much smaller than the marketing suggests. For most cardio sessions a typical person does, the calorie burn after the workout is in the tens of calories, not hundreds. A 2014 review by Swift and colleagues in Progress in Cardiovascular Diseases noted that exercise contributes to weight loss primarily through energy expenditure during the activity, and that the aerobic training volume required to produce meaningful weight loss is substantially higher than what most people doing a few short cardio sessions a week actually do.
The practical implication: don’t pick a brutal workout because you think the afterburn justifies it. Pick the workout you’ll repeat.
The Walking Caveat
The single most underrated form of cardio for fat loss is walking, and the fitness internet hates this fact. Walking doesn’t sell programs, doesn’t require equipment, doesn’t make for compelling content. It also works.
The piece Tom wrote on walking covers this better than I can from the lifestyle side. From the fitness side I’ll say this: brisk walking, daily, accumulates more meaningful weekly cardio than most people’s three-times-a-week gym cardio sessions ever do. If you walk 40 minutes a day for a year, you’ve done roughly the energy equivalent of about 220 hours of moderate cardio. Almost nobody who joins a gym does that volume in their first year. Walking quietly beats it.
What I’d Actually Do
If you’re starting from very little cardio and your goal is fat loss, the plan I’d run is the same one I eventually ran on myself, and it’s significantly less impressive than anything you’d find on Instagram.
- Walk most days. 30 to 45 minutes, conversational pace. Doesn’t have to be at once. Tom’s article on walking explains why this matters more than people think.
- One longer cardio session per week. A bike ride, a hike, a swim, a slow jog if you like that. 45 to 60 minutes at a pace you can sustain. The point is the steady work, not the heart rate.
- One shorter harder session per week, optional. If you like intervals or hill sprints or rower intervals, this is the slot for them. 15 to 25 minutes, hard but not insane. Skip this entirely if you don’t enjoy it and your weight is still moving.
- Strength training stays the same. Two sessions a week, separate from the cardio. Cardio doesn’t replace lifting for body composition.
That’s the whole plan. Boring. Effective. Sustainable for years.
The Diet Part That Always Wins
I have to say this in every fitness article I write on this site, because it’s true. Cardio doesn’t lose weight on its own at any meaningful rate. The energy cost of an hour of moderate cardio is roughly 300 to 500 calories for most adults. That’s a bagel with cream cheese. Cardio supports weight loss by raising your energy expenditure and improving how you recover, but the actual calorie deficit comes from food. Lauren writes about what holds up in the kitchen, and that’s where the weight loss work happens.
If you’re crushing cardio five days a week and eating the same way you always did and the scale isn’t moving, the cardio isn’t the problem.
What I’d Skip
I’d skip every “fat-burning zone” calculator and every workout app that tells you to stay between 60 and 70 percent of your max heart rate to “target fat.” That terminology is technically true (lower-intensity exercise uses a higher proportion of fat for fuel) but practically misleading. Higher-intensity work burns more total calories, and total calories matter more than fuel source for weight loss. The “fat-burning zone” branding has cost a lot of people a lot of time on treadmills that didn’t need to be that slow.
I’d skip the all-HIIT-all-the-time approach for anyone over 35 who’s just getting into cardio. The injury rate is higher, the recovery cost is steeper, and the results aren’t better than the boring version.
And I’d skip every cardio machine that asks for a credit card to unlock features. The cheap stationary bike, the treadmill at the basic gym, the pavement outside your house, the walking shoes you already own. All of these do the job, and they have for everyone who’s ever lost weight through cardio.
The version of me who avoided cardio for ten years missed out on a long, slow benefit that wasn’t dramatic but was real. The version of me who eventually walked his way into the habit didn’t get aesthetically transformed. He just felt better, slept better, recovered better from lifting, and saw the scale move because the diet side was finally being supported by some movement. None of it is the version Instagram sells. It’s just the version that holds up.
