On Mounjaro or Wegovy? Why strength training matters more now

If you are on Mounjaro, Wegovy or another weight loss injection, the most useful thing you can add is regular strength training. Some of the weight you lose is not fat, and strength work is the main way to hold on to muscle while the scale goes down. You do not need to be fit to start, and you do not need a gym.

Whether you should be on the jabs is a conversation for you and whoever prescribes them. This post is about getting the most out of them.

What the research found

The clearest numbers come from the main trial of tirzepatide, the drug in Mounjaro. A group of 160 participants had their body composition scanned before treatment and again after 72 weeks. On average they lost 21% of their body weight. Roughly three quarters of what they lost was fat and a quarter was lean mass (the published study).

Two things are worth knowing about that quarter. Lean mass is not all muscle, because it includes water, organs and bone as well. And the people on the placebo, who lost far less weight through diet and activity changes alone, lost the same proportion of lean mass. So the loss comes with weight loss itself rather than with the injection. The jabs simply make large weight loss far more common.

Why the muscle matters

Muscle is what makes ordinary life easy. Carrying the shopping up the stairs, getting up off the floor, keeping your footing on a wet pavement. From middle age we lose it gradually anyway, so losing extra during a big weight loss is worth taking seriously, whatever your age.

Then there is the question most people on the jabs think about: what happens when the prescription ends. Nobody can promise you an answer to that. What we can say is that the habits you build while you are on them are the ones you keep, and a fixed training time with people who expect you tends to be a habit that lasts.

What to do about it

The UK physical activity guidelines already ask every adult to do something that builds strength on at least two days a week. If you are losing weight quickly, those two days matter more than usual.

• Lift something, twice a week or more. Kettlebells, bands and your own body weight all count. A load that feels hard by the last few reps is what tells your body to keep the muscle.
• Eat enough protein. Appetite drops on the jabs, which makes it easy to under-eat protein without noticing. Ask your prescriber or a dietitian what you should be aiming for.
• Start gently. Energy can be up and down, especially in the first few weeks. Training you can repeat beats training that flattens you.
• Tell your prescriber. Let them know you are starting, particularly if you have other health conditions.

How that works at Bootcamp SE16

Strength is the backbone of what we do. Strength Squad and Functional Strength sessions run through the week at Stave Hill in Canada Water and in Bromley, and every exercise has an easier and a harder version. The coach picks your starting weight and moves it up when you are ready, not before.

You do not have to tell the group anything. If you mention the jabs when we speak before your first session, we can plan around the lower-energy days without any fuss. People come to us for all sorts of reasons, and nobody asks about yours.

If you want to hold on to the muscle you have while the weight comes off, the Trial Experience is £39 for four sessions within two weeks, and starts with a short call, so we know where you are starting from. Sessions have to be booked in advance. If you would rather see where you fit first, take our two-minute quiz on what’s really holding you back.

This is general information, not medical advice. Speak to your GP or prescriber before starting a new exercise programme.