You added cardio. You’ve been running or cycling three times a week for two months. The scale hasn’t moved — or it went up.
So you ask the question nobody wants to ask: is the cardio making things worse?
The short answer is: probably not directly. But there are three well-documented reasons why adding cardio produces dramatically less weight loss than the calorie maths would predict — and why some people genuinely end up weighing more after adding a cardio programme.
The Compensation Problem
Your body doesn’t simply burn the calories you expend during cardio and leave everything else the same. It compensates. In at least two highly consistent ways.
Appetite compensation. Most people eat more after adding cardio — sometimes consciously, through the “I earned it” logic, but more often through genuine hormonal changes. Sustained moderate-intensity cardio increases ghrelin (hunger hormone) and can reduce leptin (satiety signal) in the hours following a session. Research funded by the NIH followed participants through a 12-week supervised exercise program and found approximately 1,000 kilocalories per week of compensatory increase in energy intake. Nearly eliminating the expected fat loss from the programme entirely.
This isn’t willpower failure. It’s physiology. Your body fights to re-establish the energy balance it was maintaining before you started exercising.
NEAT reduction. After structured gym sessions, most people unconsciously reduce their spontaneous movement throughout the rest of the day. They sit more, take fewer steps, fidget less, skip the stairs. This is Non-Exercise Activity Thermogenesis — NEAT — the energy from all movement outside formal exercise. Research found that people adopting a 3x/week exercise programme reduced their NEAT more than people doing 1-2x/week — the more consistently they exercised, the more consistently their bodies compensated by becoming more sedentary elsewhere.
This is why exercise and spontaneous movement are separate variables: adding an hour of cardio doesn’t automatically mean you’re moving more across the day. For many people, it means moving the same amount — just differently distributed.
The Body Is Smarter Than Your Treadmill
There’s a third layer, and it’s the most striking.
In 2016, anthropologist Herman Pontzer published research on the Hadza — a hunter-gatherer population in Tanzania who walk miles daily as part of traditional life. His team expected this activity level to produce dramatically higher total daily energy expenditure than sedentary Western adults. It didn’t. The Hadza burned only marginally more calories per day than the average desk worker.
The finding led to the Constrained Energy Model: the body regulates total daily energy expenditure within a relatively narrow range regardless of activity level. When you add structured exercise, your body doesn’t simply stack those calories on top of existing expenditure. It compensates through slightly reduced resting metabolic rate, improved movement efficiency, and reduced energy cost of other biological processes.
A March 2026 paper in Communications Medicine confirmed this in a 12-week aerobic exercise programme: exercise induced metabolic compensation through reduced resting metabolism, improved movement efficiency, and selective shrinkage of highly metabolic organs. On average, research suggests only about 72 percent of exercise energy expenditure translates to actual increased total daily energy burn.
None of this means cardio doesn’t work. It means cardio’s effect on weight is much more complex than the display on your treadmill suggests.
What Cardio Is Actually For
Cardio does a great many things very well. It improves cardiovascular function, reduces blood pressure, lowers resting heart rate, improves insulin sensitivity, supports mood, reduces anxiety and depression risk, and protects long-term health independent of any effect on the scale.
For weight maintenance — keeping fat off once it’s been lost — regular cardio is one of the most powerful tools available. Research on people who successfully maintain significant weight loss long-term shows almost universally high levels of physical activity. Cardio is excellent at this.
What cardio is relatively poor at, on its own, is producing initial fat loss — precisely because of the compensation mechanisms above.
For body composition change, strength training has a meaningful advantage. Resistance training builds muscle, which is metabolically active tissue. It produces less appetite compensation than sustained cardio. It tends not to trigger the same degree of NEAT reduction. And the adaptations it creates — more muscle, higher resting metabolism, better insulin sensitivity — all work toward the outcome most people are seeking.
The combination consistently shown to produce the best fat loss and body composition results: strength training as the foundation, cardio as the supplement, dietary management as the primary driver of the caloric deficit.
Three Things to Do
Look at your intake first. If cardio hasn’t produced expected fat loss, appetite compensation is the most likely culprit. Adding cardio often increases calorie intake in ways that are genuinely hard to detect. If you haven’t been tracking — even roughly — you may have added both the cardio and several hundred extra calories per day without realising it. The treadmill’s calorie counter significantly overestimates your burn.
Add strength training. If fat loss and body composition are the goals, strength training is the more effective tool. Two to three sessions of resistance training per week, combined with cardio you genuinely enjoy, will produce better results than a cardio-heavy programme alone.
Keep the cardio — but know what it’s doing. Cardio is building your cardiovascular system, supporting mental health, and protecting long-term health in ways that have nothing to do with the scale. If you want the scale to move, dietary management is the primary driver. Cardio supports it — but it can’t do the work alone.
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Coach Chris Cooper is the owner of Catalyst Fitness in Sault Ste. Marie, Ontario. The Catalyst podcast releases new episodes weekly at catalystgym.com/blog.