Yes, for your cardiovascular health. Not as a way to keep muscle, and not instead of resistance training. Those are three separate answers to what people usually ask as one question.
What cardio does not do
It does not preserve lean mass. This is the misunderstanding worth clearing up first, because a great deal of exercise advice aimed at people losing weight is cardiovascular, and it does not address the muscle question at all.
Preserving muscle requires loading it. Walking, cycling, swimming and running do not provide meaningful resistance to the muscles involved, so they do not send the signal that muscle is worth keeping. Some endurance work provides a small stimulus to the legs in untrained people, and that is genuinely marginal.
It also does not accelerate weight loss much in this context. On a GLP-1 the deficit is already being driven by appetite suppression, and adding cardio to increase it further is rarely the constraint — and it pushes rate of loss in the direction associated with a worse lean split.
What cardio does do
It improves cardiorespiratory fitness, blood pressure and a range of health markers that matter independently of body composition. Those benefits are real and well established, and they are reason enough on their own.
It is also the easiest form of activity to actually do. Walking requires no equipment, no skill and very little energy — which matters on a medication that leaves many people with less of it.
Where it goes wrong
The problem is not cardio. It is cardio instead of resistance training.
Someone with limited energy, doing four cardio sessions a week and no resistance work, is spending all of their available capacity on the input that does not protect muscle while doing none of the input that does. That is a common pattern and it is worth naming, because each individual session feels productive.
If you have the capacity for two sessions a week, both should be resistance training. If you have capacity for four, do two of each.
A workable arrangement
- Two or three resistance sessions, thirty minutes each. This is the non-negotiable part.
- Walking, as much as suits you. It is low-cost, does not interfere with recovery, and is the easiest thing to sustain.
- Harder cardio, optional. If you enjoy it, do it. Keep it away from resistance sessions if energy is limited, so the resistance work gets your best effort rather than your leftovers.
On very low energy
Some weeks you will not have four sessions in you. When that happens, resistance training is the one to protect, and walking is the one to keep because it costs almost nothing.
Dropping the harder cardio for a while is not a setback. Dropping the resistance training is the one that shows up later in your body composition.
The honest summary
Do cardio because it is good for your heart and because you like it. Do resistance training because it is the only thing that tells your body to keep the muscle it has. If you only have room for one, it is not a close call.
The muscle check counts strength sessions specifically for this reason — it does not ask about cardio, because for the question it answers, cardio is not one of the inputs.