There’s a lot of noise about “the jabs” right now — excitement, fear, opinions, hot takes. But very little explanation of what these medicines are actually doing inside the body.
So let’s slow it down and start where nature intended: with the biology itself.
In a healthy body, GLP‑1 already does an important job
GLP‑1 is a hormone your gut releases every time you eat. Its job is beautifully simple:
- it tells your brain you’re full
- it slows how fast food leaves your stomach
- it helps control blood sugar
- it settles appetite between meals
In a normally functioning system, the loop looks like this:
Eat → GLP‑1 released → feel full → stop eating → appetite settles → weight stays fairly stable.
Most healthy adults already make enough GLP‑1 to do this job well. No medication required.
What changes in obesity and type 2 diabetes?
When people become obese or develop type 2 diabetes, this signalling system becomes distorted.
That can mean:
- less GLP‑1 released after meals
- or the brain becomes less responsive to it
- fullness feels weaker
- the stomach empties quickly
- hunger returns sooner
- blood sugar control worsens
Instead of a clear “I’ve had enough,” the signal becomes fuzzy.
This is not about willpower. It’s a biological feedback loop that’s gone off course.
How single‑mechanism GLP‑1 medicines help
Medicines like Wegovy and Saxenda work by mimicking one hormone: GLP‑1.
They amplify the body’s natural fullness signal sending:
- stronger message to the brain
- slower stomach emptying
- reduced appetite
- improved blood sugar control
People often describe the experience as:
- quieter food noise
- smaller portions feeling enough
- less constant thinking about food
It’s like turning the volume back up on a system that had gone quiet.
Dual‑mechanism medicines go further
Medicines like Mounjaro act on two hormones:
Medicines like Wegovy and Saxenda work by mimicking one hormone: GLP‑1.
- GLP‑1(appetite and fullness)
- GIP (energy use and insulin response)
Together, they influence:
- hunger
- blood sugar
- fat metabolism
- satiety
This is why dual‑mechanism drugs often lead to greater average weight loss in trials. But “more powerful” doesn’t automatically mean “better for everyone.” It also means more complexity — and sometimes more side effects.
Then there’s the part we don’t really talk about…
We all know eating isn’t just about hunger. If it were, this would be simple. Eating is also about pleasure, comfort, reward, anticipation — the emotional pull as much as the physical need.
And that pull is driven by dopamine — the brain chemical behind:
- wanting
- craving
- motivation
- that magnetic “pull” toward certain foods
You’ve probably realised ultra‑processed foods are very good at lighting up this system. In fact there’s a whole section of food science specifically designed to do just this. That’s part of why they’re so compelling.
What often gets missed is that GLP‑1 medicines don’t just work in the gut. They also act on the brain’s reward centres.
Which is why you hear people say things like:
- “I don’t think about food anymore.”
- “Chocolate just isn’t exciting.”
- “I forget to eat.”
It’s not just appetite that changes. The reward pull of food gets quieter.
For many people, that’s incredibly relieving — like someone finally turned down the background noise they’ve been battling for years. But it’s also a reminder: these are powerful, brain‑active medicines. Not lifestyle supplements. Not shortcuts. Not “willpower in a pen.”
They shift biology in ways that go far beyond hunger.
Why some people thrive — and others struggle
One thing that rarely makes it into the headlines is just how differently people respond to these medicines. And it’s not because one group is “better” or more disciplined. It’s because the biology they’re working with — and the life wrapped around that biology — isn’t the same.
Some people thrive because previously:
- their hunger signals were genuinely overwhelming
- their reward system was constantly switched on
- their blood sugar was swinging all over the place
- food felt like a full‑time mental load
When the medication quiets all of that, it can feel like someone finally turned down the noise. They get space. They get relief. They get a version of themselves they haven’t met in years.
Others struggle because:
- the side effects hit harder
- their emotional relationship with food is still loud
- eating has been a coping strategy for decades
- they feel disconnected from hunger and fullness
- the reward pull of food wasn’t their main challenge
- life stress, sleep, trauma or environment still drive their eating
For these people, the biology shifts — but the patterns, habits, emotions and stories underneath don’t automatically change with it.
And that’s not failure. It’s simply the reality that weight, appetite and behaviour are never only biological. They’re lived. They’re learned. They’re layered.
This is why two people can take the same medication and have completely different experiences. Same tool. Different bodies, histories, environments and emotional landscapes.
This is why behavioural change still matters
These medicines can change:
- hunger biology
- blood sugar regulation
- the reward pull of food
But they can’t teach:
- how to eat in a way that actually works for your life
- how to handle emotions without using food
- how to build habits that last longer than a prescription
- how to enjoy food without fear or overthinking
- how to live well if you ever come off the medication
This is why, (as with all weight reductions plans and tools), some people regain weight when they stop. Not because they “failed” — but because the biology changed, and the story underneath didn’t.
My bottom line
In a healthy body, GLP‑1 quietly keeps appetite in check. In obesity and diabetes, that signal weakens. These medicines turn it back up — sometimes very loudly.
Some work on one hormone. Some work on two. All of them influence both body and brain.
They’re powerful tools. They’re not cures.
The real transformation comes from understanding how we eat, why we eat, and how to rebuild a calmer, healthier relationship with food alongside the biology.
That’s the work that actually lasts.
If you missed part one you can click here for the real facts behind licenced weight-loss jabs:
Niki Kerr — a qualified nutritionist and behaviour-change specialist. I bring a thought-leader lens to Food, Nutrition and modern weight loss (including GLP-1 medications) with an evidenced focus on what actually works in real life: nourishment, consistency, and behaviour change that sticks.
