Why Cardio Alone Won't Help You Lose Weight

I had a client who ran four days a week for eight months. She was consistent, dedicated, and completely demoralized by the results. She'd lost some weight initially, then plateaued. Her appetite was through the roof. She felt tired all the time.

This is an extremely common experience. And it's not her fault — she was doing exactly what she'd been told.

The Compensation Problem

Cardio burns calories. That's true. But it also makes you hungry — more hungry, in many cases, than the calories you burned justify. The body is very good at protecting its weight. When you consistently burn extra calories through cardio, it often compensates by increasing appetite and reducing unconscious movement throughout the rest of the day.

Research by Dr. Herman Pontzer and colleagues on the Hadza hunter-gatherers showed that total daily energy expenditure is surprisingly similar across activity levels — because the body downregulates background activity when structured exercise goes up. This is called the constrained energy expenditure model. It explains why many people who take up running don't lose as much weight as the calories-burned math would predict.

Muscle Drives Metabolism

Cardio burns calories during the session. Muscle burns calories constantly — at rest, while you sleep, during the hours between workouts. A pound of muscle burns approximately 6 to 10 calories per day at rest. That doesn't sound like much, but across 10 to 15 pounds of lean muscle (a realistic two-to-three-year adaptation from resistance training), it adds up to 60 to 150 additional calories burned every day without any extra effort.

More importantly, muscle preserves your metabolic rate as you age. Cardio does not build muscle. Cardio does not prevent the muscle loss that comes with aging and low protein intake. Only resistance training does.

What Cardio Is Actually Good For

I'm not anti-cardio. Cardiovascular exercise is excellent for heart health, stress reduction, mental clarity, and endurance. Walking in particular is one of the most underrated health behaviors that exists — low impact, accessible, and supported by a mountain of research on longevity and metabolic health.

Cardio is a great supplement to a training program. It's a poor foundation for one.

The Combination That Works

Two to three strength training sessions per week is the foundation. Add walking — 7,000 to 10,000 steps per day is a target I use with clients — as your aerobic base. Throw in a cardio session or two if you enjoy it. This combination builds muscle, maintains cardiovascular health, manages appetite better than cardio alone, and produces results that actually stick.

The woman who was running four days a week with no results? We replaced two of those runs with lifting sessions, kept two as walks, and adjusted her protein intake. She was down 14 pounds in four months. Same amount of time invested. Very different approach.