The Fat Jab: What Nobody Tells You - And Why Strength Training Is Essential

My personal trainer perspective, informed by client Jay currently taking the jab.

Wegovy. Ozempic. Mounjaro.. What is actually happening inside the body of someone on these medications, and what does that mean for how they should train?

I recently had that conversation with Jay.

Jay has been on Wegovy and shared some very insightful feedback about his experience. This reframed a lot of my thinking around the jabs.

What Are These Medications?

Semaglutide-based medications like Wegovy and Ozempic work by mimicking a hormone called GLP-1, which regulates appetite and insulin response.

In simple terms, they dramatically reduce hunger signals, slow gastric emptying, and help the body feel full far sooner than it normally would.

The result, for many people, is significant and sustained weight loss.

But alongside this there can also be a big, disorienting shift in how your body relates to food and energy.

What Jay Taught Me

Jay described realising that you can do everything right including calorie deficit, tracking, exercise, nutrition, sleep, yet, still fail multiple times.

Sometimes, he said, sheer willpower just isn’t enough. For some people, medical assistance is a legitimate, doctor-recommended tool. It is not a shortcut, it's another tool.

We live in a culture that puts willpower on a pedestal and moralises weight loss. But when someone has tried repeatedly, done everything by the book, and still not succeeded, the problem may be neurological and hormonal and not about motivation. GLP-1 medications address that physiological barrier in a way no amount of discipline can.

What Jay also made clear, though, is that the medication brings its own challenges that require just as much discipline and awareness.

Jay's energy has become unpredictable and his appetite has been suppressed so significantly that he now sets alarms to remind himself to eat. And crucially, he’s learned that what worked for him nutritionally before doesn’t work the same way on Wegovy.

The Protein Problem

One of the most important things Jay highlighted was protein intake. On these medications, food consumption drops dramatically.

If you’re not actively prioritising protein the rapid weight loss will pull heavily from muscle mass, not just fat.

This is one of the most overlooked risks of weight loss medications. The number on the scale goes down, but the composition of that loss matters enormously. Lose muscle alongside fat and you end up metabolically weaker, physically softer, and in cases of significant weight loss at greater risk of loose, excess skin (that may ultimately require surgical intervention).

Jay also flagged hydration. The medication affects how the body processes food, and significantly increased water intake is essential to support digestion and overall function.

Why Exercise Isn’t Optional

This is where personal training becomes not just beneficial, but arguably essential for anyone on such medication.

Muscle preservation.

Resistance training is the single most effective tool for preserving lean muscle during a calorie deficit. Without it, the body has no signal to hold onto muscle tissue. With it, you’re telling the body: this muscle is being used and so the body keeps it.

For someone losing weight rapidly, consistent strength training is the difference between emerging leaner and stronger, or lighter but weaker.

Body composition over body weight.

The goal was never just to weigh less. It was to look better, feel better, move better, and be healthier. A structured training programme shapes the body as the fat leaves, building tone, improving posture, increasing functional strength.

Energy regulation.

Jay mentioned his energy being unstable. Exercise, when programmed appropriately, is one of the most reliable regulators of energy, mood, and sleep quality. Strategic training (not when excessive / exhausting, but consistent) can help stabilise what the medication disrupts.

Metabolic protection.

Rapid weight loss without exercise slows the metabolism over time. Muscle is metabolically active tissue which means the more you have, the more calories your body burns at rest. Protecting and building muscle during this process safeguards your long-term metabolic rate and makes maintaining the weight loss far more sustainable.

Mental resilience.

Weight loss journeys are psychologically demanding. The structure of a regular training programme, the visible progress in strength and fitness, and the sense of agency that comes from consistent effort all contribute meaningfully to mental wellbeing. Jay's workouts are going well and that matters, perhaps more than the number on the scales.

Jay says that these medications should be seen as another tool, not a shortcut.

These medications are not magic. They are a powerful lever that lowers one barrier -appetite but they do nothing to build fitness, preserve muscle, improve cardiovascular health, or develop the habits and physical capacity that make a healthy life sustainable long term.

If anything, its more important to get the exercise side right. Because the body is changing faster, the window for influencing how it changes, in terms of composition, strength, and tone, is narrower.

I would recommend that people on these medications prioritise resistance training to protect muscle, programme sensibly, increase protein targets significantly, and monitor how the body is responding week by week.

Used alongside structured exercise, sound nutrition, and good coaching, these medications can be transformative.

The jab might reduce the hunger. But it's your training that builds the body.