The "Off-Switch" That Changes Everything
Disclaimer: This article is for educational and coaching purposes only. It’s designed to help clients and fitness professionals to understand how GLP-1 medications can affect appetite, training, performance, and body composition. It is NOT medical advice, and it doesn’t replace guidance from your General or Health Practitioner.
TL;DR
Coaching Role Shift: As coaches, we’re no longer driving the calorie deficit; we’re building the surrounding infrastructure (muscle, habits, overall health) that GLP-1 medication, in isolation, cannot yet provide.
The “Caloric Floor”: GLP-1s can cause extreme, unintentional calorie deficits. Coaches must help to ensure that clients eat enough to support metabolic health and prevent symptoms of Relative Energy Deficiency (RED-S).
Muscle is the Priority: With 20-40% of weight loss potentially coming from lean mass, heavy resistance training and high protein (1.6-2.0g/kg/BW) are seemingly non-negotiable.
Managing the Medication: Training needs to be adapted for symptoms associated with delayed gastric emptying (nausea) and blunted thirst cues (dehydration).
The Bigger Picture: Recent 2025/26 trial data shows these medications are “disease-modifying agents” that reduce inflammation, protect the brain, and dampen addictive behaviours—far beyond just weight-loss.
Let’s call it what it is: GLP-1s are everywhere in the past year or so.
You can’t turn on the TV, open a paper, or read a magazine without seeing them mentioned. And the question of “who’s on it?” seems to have become normal office and school pick-up chatter. I’ve personally got clients using them, plenty more who have mentioned the drugs in conversation, or have asked for my opinion on usage.
This article isn’t about the decision to use, or not to use, GLP-1s primarily from a body composition perspective. But to look at these medications through a coaches lens and how to better support clients that do make the decision to use.
The aim of this post is therefore to establish: what they are in plain English, a brief historical perspective, what they can do to body composition (especially lean mass), why protein and resistance training become close to non-negotiable, and how we manage both the effects and the side effects inside real-world training.
Thanks for reading! Subscribe for free to receive new posts and support my work.
The “Incretin” Paradigm: A Brief History
To understand the actions of this class of drug, you need to understand Incretins.
Plain English Definition: Incretins are metabolic “messenger” hormones released by your gut when you eat. They tell your pancreas to release insulin, tell your brain that you’re full, and tell your stomach to slow down.
Glucagon-like peptide-1 (GLP-1) is the “lead” messenger. These medications we see today, glucagon-like peptide-1 receptor agonists (GLP-1 RAs), essentially turn the volume up on these signals, making the body feel fuller, for longer, on much less food intake.
The pharmacological evolution of GLP-1s has fundamentally shifted the landscape of not only obesity management, but also metabolic health. For those involved within the health and fitness space, understanding this evolution is critical to safely and effectively programming for clients utilising these medications, and actually working collectively with the human-being in-front of you.
The trajectory of these drugs can broadly be categorised into three phases of development:
First and Second Generation (Mono-agonists): First-generation drugs like exenatide (brand names Byetta/Bydureon) required daily injections and offered modest overall effects. The breakthrough in the space came with second-generation agents like the now commonly known semaglutide (brand name Wegovy/Ozempic), which extended the half-life towards once-weekly dosing. These agents target only the GLP-1 receptor, which helps in slowing gastric emptying (how fast food moves through the digestive tract), increasing insulin sensitivity, and reducing appetite, leading to average body weight reductions of 15-17% across multiple studies within human populations (example study here).
Third Generation (Dual and Triple Agonists): The current frontier involves medications that target multi-receptor agonists. Drugs such as tirzepatide (brand name Zepbound/Mounjaro) are dual agonists targeting both GLP-1 and GIP (Glucose-dependent insulinotropic polypeptide) receptors, which has shown in research to result in weight loss up to 22.5% (study link here). Experimental triple agonists, such as retatrutide (targeting GLP-1, GIP, and glucagon), are pushing boundaries even further with increasingly less side effects (study link here).
Combinatorial Platforms: Looking slightly further into the future, drugs like CagriSema, combine semaglutide with an amylin receptor (a hormone that also regulates appetite, enhances satiety, slows gastric emptying, and suppresses glucagon), showing up to 22.7% weight loss in clinical trials as recent as 2025 (study link here).
As these medications suppress appetite to unprecedented levels, the role of a coach within the health and fitness space is pivoting from merely helping create a caloric deficit, towards meticulously managing speed of body composition changes, recovery, muscle mass preservation, and a more holistic approach to a clients overall health.
Nutrition Coaching and Managing a GLP-1 Client
When a client is prescribed a GLP-1, the traditional nutrition coaching paradigm of “eat less, move more” is essentially flipped. The medication is forcefully driving the “eat less” component of the equation, creating unique nutritional challenges.
Managing the Calorie Deficit and Setting Estimates
Because GLP-1s powerfully blunt hunger cues, clients can easily fall into severe, unintentional calorie deficits—often consuming as low as 800-1000kcal per day. In active individuals, this is mimicking a low-grade bodily starvation, and can lead to symptoms that begin to resemble Relative Energy Deficient in Sport (RED-S), including severe fatigue, hormonal disruption, and likely plummeting performance in the gym setting. The coaches role, must be to help clients understand the need for a conservative caloric floor, ensuring that they eat enough to support basic metabolic function and recovery, rather than allowing the medication to subconsciously drive them into potential extreme deprivation.
Protein Intake is Paramount
With severe caloric restriction, such as that seen in higher-dose GLP-1 usage, the body rapidly catabolises lean tissue. To offset this, protein intake must become an absolute priority for the client. Current clinical consensus for those individuals on GLP-1 medications (link here), as well as the broader population at large, is a recommended intake of daily protein of 1.2-1.6g per kg of bodyweight, and this can be increased further towards 1.8-2.0g/kg/BW for those engaged in consistent resistance training.
From a anecdotal standpoint, it’s rare that clients consistently meet these requirements initially without some form of intervention/conscious tracking, even prior to GLP-1 medication usage…
Tracking Subjective and Objective Health Markers
Because hunger is no longer a reliable cue for energy needs, it’s likely individuals with need to track other metrics to ensure adequate fuelling:
Subjective Markers: Track daily energy levels, mood stability, sleep quality, and cognitive focus. A sudden drop in any of these likely indicates that the caloric deficit has become too aggressive.
From a personal perspective, we’ll utilise either a more formal “Pre-Session Check-In Form” with some simple 1-10 scaled metrics which we can use to track against session performance. Or alternatively, a simple 3-5 question verbal check-in (“How are your energy levels today?”, “How’s digestion been the last few days”…) depending on the individuals preference.
Objective Markers: Monitor gym performance (eg., maintenance of strength levels or performance inside rep ranges), resting heart rate where possible, and hydration status (via urine colour). GLP-1s reduce the natural sensation for thirst, likely making clients more susceptible to dehydration across the day.
Dose Scaling, Cost/Benefit, and Metabolic Adaptation
The standard medical protocol for GLP-1s involves the gradual escalating of dose to the maximal tolerable limit. However, from a coaching and anecdotal perspective, pushing towards the maximal possible dose, or moving through scaling too aggressively, isn’t always the optimal. Higher doses, as expected, increase the risk of gastrointestinal (GI) side effects, severe fatigue, and excessive lean mass loss.
There’s a growing trend toward “micro-dosing” or finding the minimum effective dose. If a client is successfully losing body fat at a sustainable rate, maintaining muscle mass, and building healthy habits on a lower dose, staying at that level may offer a better cost-to-benefit ratio overall. This approach has the potential to minimise side effects, in all honestly saves the client money if paying privately, and reduces the risk of extreme metabolic adaptation.
Crucially, if a client does stop the medication abruptly without having to build a more sustainable foundation in terms of dietary and nutritional habits, clinical data shows they may regain the majority of the weight—primarily as fat mass—within a year or so.
Strength and Conditioning on GLP-1s
It’s estimated that between 20% and 40% of the total weight loss on GLP-1 medications can come from lean body mass (LBM). Resistance training is therefore the only non-pharmacological mechanism available to halt this decline in muscle loss.
Adjusting Volume and Intensity
For those individuals on a GLP-1s operating in a significantly energy-depleted state, programming needs to shift from high-volume metabolic conditioning towards higher-intensity, lower-volume strength preservation.
Intensity: Training at or above 65% to 85% of 1RM becomes critical. Heavy mechanical tension is the primary signal through resistance training that signals to the body to preserve muscle tissue.
Volume and Frequency: Because systemic recovery is likely going to be compromised by the low calorie intake, volume should be reduced. A focus on 2-4 working sets of primarily compound movements (multiple working muscles) per movement pattern, spread across 2-3 full body sessions is enough to keep the signalling for muscle retention high.
Duration: Shorter, focused sessions (30-45mins) are likely to be superior than 60-90min workouts. Prolonged training durations are going to quickly exacerbate medication-induced fatigue.
From an anecdotal perspective, the 40-45min mark seems to be enough to get a solid warm-up, and 2-4 sets of an A/A, B/B, C/C pairing of alternating upper body and lower body exercises.
Managing “Body Aches” and Muscle Soreness
Many individuals report generalised “body aches” or heightened muscle soreness when initiating GLP-1 usage. While unlikely to be caused by true muscle damage as you might experience after a high-volume gym session, it can still be alarming for those first experiencing it.
Dehydration and Electrolyte Shifts: Alongside the blunted thirst cues previously mention, reduced food intake is also going to lower essential minerals such as sodium, potassium, and magnesium, which can contribute to muscular cramping, and the generalised sensation of “aching”.
Metabolic Shifts: With the effects of the medication taking place, the body is having to rapidly adjust to the new ways of processing energy and mobilising stored body fat. Ensuring proper hydration (potentially with added electrolytes) day-to-day, especially on injection and exercise days, can be a useful way to mitigate these effects.
3. Working Around Gastrointestinal Distress
With the delayed gastric emptying as a primary feature of these drugs, meaning food is sitting in the digestive tract for longer, exercising on a full stomach can frequently trigger severe nausea or reflux-type sensations.
From an anecdotal perspective, I’ve seen these situations mostly tied to the 24-48hr after a client has injected, or in time periods around the adaptation to an increase in dosage (eg., moving from 5mg - 7.5mg) and a resulting increase in side effects.
A few ways that could potentially offset some of these distress symptoms include:
Meal Timing: Advising clients where possible to consume a pre-workout meal 2-3 hours before training to allow for at least partial digestion to take place.
Food Choices: Pre-workout meals seem to work best when there; small, bland, and low in fats and fibre, as fats heavily delay digestion and can exacerbate nausea.
Intra-workout: If a client feels nauseous during a session, extend out rest periods (2-3mins), remove exercise pairings such as Compound or Supersets, and reduce the total demand on intra-abdominal pressure (eg., swapping a Safety Bar Squat for a Goblet Squat).
Another anecdotal consideration is alternating the dynamic/tempo the activity. A quick example being a high-rep Split-Squat, in which there’s a lot of physical movement, changes in height, and internal pressure shifting; towards activities that keep the individual primarily stationary (eg., seated/standing/kneeling) whilst exercising.
Beyond “Skinny Jabs”: Systemic Health and Disease Modification
First, I’ll be honest: I loathe the term 'Skinny Jabs.' It’s a reductive label that fuels the lingering stigma surrounding GLP-1 usage. The reality, backed by landmark 2025 and 2026 clinical data, is that these aren't just cosmetic weight-loss tools—they’re profound, systemic disease-modifying agents.
Their influence on human health is far more expansive than researchers seemed initially to have imagined when solely used for glycemic control within diabetic populations. And as coaches, this changing landscape allows us to reframe these medications as a valuable asset in a client’s long-term health strategy.
Systemic Inflammation and Organ Protection
GLP-1 receptors, the primary targets of these medications, are located on immune cells as well as the vascular endothelium (a thin single-cell layer than lines your entire circulatory system). Activation of these receptors suppresses inflammatory pathways and lowers systemic C-reactive protein (CRP), a marker of inflammation commonly found on most blood tests.
The landmark SELECT trial showed that semaglutide (a Gen. 2 GLP-1) reduces the risk of major adverse cardiovascular events by 20%. Crucially, and the part that makes this most interesting in the non-medical space, is that researchers calculated that a significant portion of this cardio protection was completely independent of the amount of bodyweight a patient lost, showing that the medication itself was directly protecting heart and blood vessels.
Cognitive Protection and Neuro-degeneration
These medications cross the blood-brain barrier, lowering neuro-inflammation (inflammation of the brain) and improving cellular energy within the brain itself. While some Alzheimer’s trials (like EVOKE) have shown mixed results, a late 2025 trial from Imperial College London demonstrated that the GLP-1, liraglutide, resulted in nearly 50% less brain volume loss, and an 18% slower decline in cognitive function over the period of the trial (study link here).
Altering Addictive Behaviours
GLP-1s have been shown to act heavily on the brain’s mesolimbic reward system. By doing so, they eliminate “food noise”—those constant, intrusive thoughts about eating that so many individuals report anecdotally when trying to alter nutrition. Fascinatingly, and something I’ve personally speculated on with clients, is that this mechanism extends outwards towards other compulsive behaviours.
Recent 2025 trials (study link here) have show that low-dose semaglutide usage can reduce alcohol cravings and overall drinking intensity by nearly 50% in patients with alcohol use disorders. The research into this behavioural aspect of GLP-1 usage is also showing similar dampening effects on smoking, substance use, binge eating, and even gambling.
There’s an element of “brain rewiring” occurring with usage that’s impossible to ignore.
Lifespan Enhancement?
Finally, longevity researchers are examine GLP-1s as true “gerotherapeutics” (drugs that extend lifespan). Again, recent trials (study link here) of these medications suggest that they can physically decelerate DNA methylation-based epigentic clocks, and reduce the Senescence-Associated Secretory Phenotype (SASP)—the toxic inflammatory signals that are emitted by aging cells in the body. By forcing the body to clear our damaged cellular debris, these medications may fundamentally improve human lifespan independent of their impact on the weighing scale alone.
Conclusion
Ultimately, the 'Off-Switch' provided by GLP-1s is a powerful tool—likely more impactful than we currently realise—but it is not a complete solution. As coaches, our role has shifted from being the gatekeepers of the calorie deficit to being the architects of the infrastructure that supports a client’s overall wellbeing. We should appreciate and understand our role within this process.
The medication can quiet the noise and move the needle on the scale, but it cannot lift the weights, it cannot choose the protein-dense meal, and it cannot build the skeletal muscle that serves as a client’s ultimate insurance policy for longevity (as we explored in Anabolic Resistance).
In this environment, we’re no longer just coaching individuals through a weight-loss phase; we much closer to helping them navigate a systemic upgrade internally. In this new era, the medication may be a dramatic catalyst for change, but the work done on the gym floor still remains the foundation we still need to build upon.
AK.