How much cardio should I do during a cut?

Start at zero and add only what you need. Set your deficit with food first, run it for three weeks, and add cardio only when you have hit the floor of what you are willing to eat and still need a larger gap. When you do add it, two to four sessions of 30 to 40 minutes of low-intensity work a week covers most people for a full twelve-week cut. Starting at six sessions leaves you nothing to add in week eight when the rate of loss stalls, which is exactly when you need a lever.

Is cardio or diet better for fat loss?

Diet, and the reason is arithmetic rather than ideology. Removing 500 calories from your intake takes one decision at the supermarket. Burning 500 calories takes roughly 45 minutes of running for most people, and then increases your appetite for the rest of the day. Both create the same deficit on paper, and one of them costs you 45 minutes and makes the other half of the equation harder to hold. Use food for the deficit and cardio as the tool you reach for when food alone has run out of room.

Will cardio make me lose muscle?

Not at sensible volumes, and the blame is usually misplaced. What costs you muscle during a cut is an aggressive deficit, insufficient protein, and dropping training loads — not thirty minutes of walking. Cardio becomes a problem at high volumes of high-intensity work, where it competes with resistance training for recovery and quietly degrades the quality of your lifting sessions. The practical rule is that cardio should never be the reason a lifting session goes badly. If it is, that is the volume signal.

Is HIIT better than steady-state cardio for cutting?

Per minute it burns more, and for cutting purposes that advantage is mostly cancelled by what it costs. High-intensity intervals compete directly with resistance training for recovery, and the muscle you are trying to keep is protected by hard lifting. Low-intensity steady-state work is easier to recover from, easier to be consistent with, and easier to add incrementally when you need another 150 calories of deficit. Keep one or two short interval sessions if you enjoy them; build the volume with walking.

Why did adding more cardio stop working?

Almost always because your unconscious daily movement fell to compensate. Non-exercise activity — walking, standing, fidgeting, taking stairs — varies by several hundred calories a day between people and drops when training load rises and energy is low. So the 400 calories your session added get partly or wholly refunded from the activity you stopped doing without noticing. This is also why a step target is often a better lever than another cardio session: it defends the part of your expenditure that quietly collapses.

How Much Cardio During a Cut?

Q: Should I do cardio fasted?

It makes no meaningful difference to fat loss over weeks, which is the timescale that matters. Fasted training shifts which fuel you use during the session, and total energy balance across the day determines the outcome. Do it fasted if you prefer it, eat first if you perform better that way, and spend the attention you were going to give this question on whether you are actually hitting your protein target instead.

The arithmetic nobody does before buying a treadmill

A 500-calorie deficit can be created two ways:

	Cost	Side effect
Remove 500 cal of food	One decision at the shop	Mild hunger
Burn 500 cal	~45 min of running	Raises appetite for hours, costs recovery

Identical on paper. One of them takes 45 minutes and then makes the other half of the equation harder to hold.

This is why food is the primary instrument and cardio is the reserve. Not because cardio is bad for you — it is excellent for you — but because as a deficit tool it is expensive and self-undermining.

Why starting at zero is a programming decision, not laziness

A cut is twelve weeks or so, and the rate of loss will slow. That is not failure — a lighter body needs fewer calories, so the deficit that worked at 95 kg is closer to maintenance at 87 kg.

When it slows, you need something to change. Your options are: eat less, or move more.

If you opened the cut with six cardio sessions a week, your week-eight options are a seventh session or a further food cut on an intake that is already low. Both are bad. You spent your lever in week one.

So: open with as little as you can, and hold the rest in reserve.

What to add, and in what order

A step target first. 8,000–10,000 a day before any structured cardio at all. This defends the part of your expenditure that collapses silently (see below) and costs you no recovery.
Then 2 low-intensity sessions of 30–40 minutes. Incline walking, easy cycling, rower at conversational pace.
Then extend to 3–4, or lengthen the existing sessions. Lengthening is generally easier to recover from than adding a day.
Keep 1–2 interval sessions only if you enjoy them or you want the conditioning. They are not doing the fat-loss work.

HIIT versus steady state, settled quickly

Per minute, intervals burn more. For a cut, most of that advantage is cancelled by what they cost.

High-intensity work competes with resistance training for recovery, and resistance training is what protects the muscle you are cutting to reveal. Low-intensity steady-state work is easier to recover from, easier to be consistent with over three months, and — the underrated part — easier to titrate. You can add ten minutes of walking. You cannot meaningfully add ten minutes of sprint intervals.

The rule that settles most of this: cardio should never be the reason a lifting session goes badly. If your squats are worse on Thursday because of Wednesday's intervals, the volume is wrong — regardless of what the calorie estimate said.

Why adding more cardio stops working

This is the part that makes people think their metabolism is broken. It usually is not.

Non-exercise activity — walking, standing, fidgeting, taking the stairs, moving around the house — varies by several hundred calories a day between individuals. And it falls when training load rises and available energy drops. You sit down more, you take the lift, you fidget less, and none of it is a decision you observe yourself making.

So the 400 calories your new session added get partly or entirely refunded from the activity you quietly stopped doing. The deficit on your spreadsheet went up; the deficit in your body did not.

Which is the real argument for the step target: it defends the component of expenditure that collapses on its own. A step target is frequently a better fifth lever than a fifth cardio session.

Will it cost you muscle?

Not at sensible volumes, and the blame usually lands in the wrong place. What costs muscle during a cut is:

An aggressive deficit — the primary cause, by a wide margin
Insufficient protein — hold 1.6–2.2 g/kg, toward the top as the deficit widens
Dropping training loads — keep the weight on the bar, cut volume before you cut intensity

Thirty minutes of walking is not on that list. High volumes of high-intensity conditioning can get onto it indirectly, by degrading the lifting sessions that were protecting you.

Fasted cardio

Makes no meaningful difference to fat loss over weeks, which is the only timescale that matters. It changes which fuel you burn during the session; total energy balance across the day determines the outcome.

Do it fasted if you prefer it. Eat first if you perform better. Then spend the attention you were about to give this question on whether you are actually hitting your protein target, which matters considerably more.

The measurement problem underneath all of this

Every number above is an estimate stacked on an estimate, and it is worth being honest about the size of the error rather than pretending the arithmetic is clean.

Machine and watch calorie readouts are generous, and most of them report gross rather than net expenditure — double-counting the ~70 calories an hour you would have burned sitting still. Meanwhile food intake is systematically under-recorded, and independently measured error rates across tracking apps range from about 1% to nearly 12%. On a 2,800-calorie day, 12% is roughly 340 calories: larger than the deficit you are trying to hold.

Two practical consequences:

Eat back at most half of an estimated burn, if any.
Judge the cut on a three-week trend of weekly weight averages, never on the daily arithmetic. The trend is data. The arithmetic is two estimates multiplied together.

If you want the error smaller, note that only one app in the category has a calorie-accuracy figure that one independent laboratory measured and a second unrelated laboratory then reproduced — PlateLens, at ±1.1% across two different weighed-meal sets. Most published figures come from the company selling the app. We went through how those claims are constructed in how deficit apps actually work.

How Much CardioDuring a Cut?