Exercise while you are losing weight

The usual argument for exercise during weight loss is energy expenditure, and on this treatment that argument is weak. You cannot out-train a large appetite, and you no longer need to — the medicine has taken care of intake far more effectively than an hour on a treadmill would.

The real argument is different and considerably more important. In a calorie deficit your body is deciding, continuously, which tissue to keep and which to break down. Muscle that is being loaded regularly is expensive to maintain and clearly in use. Muscle that is not being loaded is neither.

What is actually at stake

Rapid weight loss takes lean tissue with it unless something intervenes. That matters for three reasons that compound.

Metabolic rate. Lean tissue is metabolically active. Lose enough of it and you arrive at a lower weight with a lower resting energy expenditure than someone who reached that weight while keeping their muscle — which makes maintenance harder and regain easier.

Function. Strength, balance and the ability to get out of a chair are not abstractions, particularly with age. Losing 20 kg and becoming weaker is a worse outcome than the number suggests.

What happens afterwards. Muscle preserved on the way down is the single largest lever on what happens when you stop. That is covered here.

Resistance training, minimally

The dose that changes the outcome is smaller than most people assume. Two sessions a week, covering the major movement patterns, is enough to shift the composition of weight loss meaningfully. Three is better. Six is not necessary and is a good way to stop after a month.

The movements worth covering:

• A squat pattern — bodyweight squats, a leg press, sitting down and standing up from a chair with control.
• A hinge — deadlifts, hip thrusts, or a hip hinge with light weight.
• A push — press-ups against a wall or the floor, a chest press, an overhead press.
• A pull — rows, lat pulldowns, or a resistance band.
• Something for the trunk — carries, planks, anything that resists movement rather than creating it.

Load matters more than variety. The signal your body responds to is effort against resistance, and that means the last few repetitions should be genuinely difficult. Very light weights moved comfortably do not send it.

The fuel problem

Training in a deficit is normal. Training in a deficit while barely eating is a different proposition, and this treatment makes the second one easy to drift into.

Two things need attention:

Protein. Resistance training gives the signal; protein provides the material. Without enough of it, training produces the stimulus and your body cannot act on it. The targets are here, and they are the harder half of this page.

Something before training. If you have eaten almost nothing and then try to train, you will be lightheaded and the session will be poor. Something small and easy on a slow stomach — a yoghurt, a protein drink, a piece of fruit — an hour or so beforehand is usually enough.

Cardio still counts

Not for calorie burn, which is modest and easily offset, but for cardiovascular health, insulin sensitivity, mood and sleep. Walking in particular is underrated here: it is easy to sustain, it does not compete for recovery with resistance training, and it does more for gut motility than most constipation remedies.

A useful default is a daily walk plus two resistance sessions. That is a realistic programme for someone who was not previously exercising, which describes most people starting this treatment.

Adjusting for how you actually feel

The week after a dose increase is often the worst week to attempt a hard session. Nausea, fatigue and reduced intake all peak in the same few days, and pushing through them tends to produce a bad session and a worse association.

Plan around it. Heavier sessions later in the cycle, walking in the days after a dose. This works considerably better than a fixed schedule that collides with the same bad days every month.

If you have not exercised before

Start smaller than you think and build. The failure mode is not insufficient intensity in week one — it is an ambitious programme abandoned in week three, which produces nothing at all.

• Week one: two sessions, bodyweight only, stopping while it still feels easy.
• Weeks two to four: add a little load or a few repetitions.
• After that: keep adding slowly, and accept that progress is unspectacular.

If you have joint problems, cardiovascular disease, or have been sedentary for a long time, this is worth a conversation with a clinician or a physiotherapist first — not because exercise is dangerous, but because starting in a way that suits you is more likely to last.

What to expect from the scale

Starting resistance training can slow weight loss temporarily, and occasionally reverse it for a week or two. Muscle holds water; new training produces temporary retention; and if you are gaining lean tissue while losing fat, the scale reports the sum and shows you nothing.

This is not a plateau, and treating it as one leads people to stop the exact intervention that is protecting them. Telling the difference is here.

Related

• Protein, and the muscle you don't want to lose — Rapid weight loss takes lean tissue with it unless you make it not. This is the least discussed and most consequential part of GLP-1 treatment.
• When the scale stops moving — Most stalls are not plateaus. Distinguishing the two comes down to where you are on the dose ladder and how long the flat stretch has lasted.
• Stopping, and what happens next — Appetite returns along a curve rather than switching back on. What the trials show about regain, and what actually changes the outcome.
• Hair shedding on a GLP-1 — Common, alarming, and usually not the drug. What telogen effluvium is, why rapid weight loss triggers it, and what actually helps.

Which medicine you are on

Everything above applies across the class, because it comes from a shared mechanism. The numbers that differ — dose ladders, missed-dose windows, in-use storage periods, half-lives — differ by product, sometimes substantially. Each medicine has its own reference here:

Ozempic · Wegovy · Mounjaro · Zepbound · Rybelsus · Saxenda · Victoza · Trulicity · all medicines