The GLP-1 Question: A Coach's Honest Take on the Trade-Offs Few Doctors Explain

What 45% lean mass loss, 2.6% bone density loss, and two-thirds weight regain actually mean for your body

Lately, I’m getting the same question over and over again, “Should I take GLP-1’s?” Only last week, three different people asked me the same thing.

“Should I get on Ozempic?”

“My doctor wants to start me on a GLP-1 — what do you think?”

“Everyone’s losing weight on these drugs. Am I missing out?”

Two of those three were women. That detail matters more than you might think, and we’ll get to why.

I want to be careful here. I’m not a physician. I don’t write prescriptions, and I don’t tell people what to put in their bodies. But I am a two-time cancer survivor who tried in the past years different nutrition protocols, I’m a Precision Nutrition certified coach, and I’ve been having this same conversation enough times that I want to put my honest take in one place.

Because here’s what I keep noticing: people are walking out of doctors’ offices with a prescription, an injection schedule, and almost no understanding of what the drug actually does, or what it costs them on the way down.

That’s the conversation we’re not having. Let’s have it.

A diabetes drug that became something else

This is the first thing most people don’t know.

GLP-1 receptor agonists were never designed for weight loss.

The hormone itself, glucagon-like peptide-1, was identified in the early 1980s as part of the body’s blood sugar control system. The first synthetic version, exenatide, was derived from the saliva of the Gila monster (a venomous lizard that can survive long periods without food). It received FDA approval in 2005 and EMA approval in 2006, both for one indication: type 2 diabetes.

The trail follows the same pattern across the major molecules.

Original indication: type 2 diabetes

• Exenatide - FDA 2005, EMA 2006

• Liraglutide (Victoza) - FDA 2010, EMA 2009

• Semaglutide (Ozempic) - FDA 2017, EMA 2018

• Tirzepatide (Mounjaro) - FDA 2022, EMA 2022

Repurposed at higher doses for obesity:

• Liraglutide as Saxenda - FDA 2014, EMA 2015

• Semaglutide as Wegovy - FDA 2021, EMA January 2022

• Tirzepatide as Zepbound (Mounjaro for obesity in EU) - FDA 2023, EMA 2024

The weight loss was an observed side effect during the diabetes trials. Patients with type 2 diabetes were losing weight on these drugs, and the pharmaceutical companies, correctly identifying a much larger market than diabetes alone, ran new trials at higher doses for the obesity indication. The molecule didn’t change. The dose went up, the marketing pivoted, and a diabetes drug became a weight loss drug.

This isn’t a conspiracy theory or a “Big Pharma” rant. It’s the regulatory record on both sides of the Atlantic. But it does change how I think about the conversation. When a drug developed for one disease gets repurposed at higher doses for a different disease in a much larger population, most of whom have never been screened for the metabolic dysfunction the drug was originally designed to address, the burden of proof on long-term safety should be high. In practice, it hasn’t been.

It’s also worth knowing the EU continues to expand the indication, not narrow it. In December 2025, the European Commission approved a higher 7.2 mg dose of Wegovy that produces an average 20.7% body weight loss over 72 weeks. Whether that’s progress or escalation depends on what trade-offs you’re willing to accept, and whether anyone explained them to you.

What GLP-1 drugs actually do

GLP-1 (glucagon-like peptide-1) is a hormone your gut releases after you eat. It tells your pancreas to release insulin, slows down how fast food leaves your stomach, and signals your brain that you’re full.

GLP-1 receptor agonists are synthetic molecules that mimic that hormone, but at much higher and more sustained levels than your body would ever produce on its own.

Here’s what they do mechanically:

• They activate GLP-1 receptors in your brain, specifically in areas that regulate appetite and reward. You feel full faster and stay full longer.

• They slow gastric emptying dramatically. Food sits in your stomach much longer than it normally would.

• They dampen hunger signals, including your body’s natural drive to seek food.

The net effect is simple: you eat a lot less. And when you eat a lot less, you lose weight. That’s the magic, and that’s also where the trade-offs start.

The lesson from 1944, we keep forgetting

In 1944, a physiologist named Ancel Keys ran what became known as the Minnesota Starvation Experiment. Thirty-six healthy men were placed on a diet of roughly 1,570 calories per day for 24 weeks, a moderate restriction by today’s “weight loss” standards.

What happened wasn’t subtle. Participants lost about 25% of their body weight. Their basal metabolic rate dropped by around 40%. They lost significant muscle mass. Their hearts shrank. Their hormones cratered: testosterone, thyroid, libido. They became obsessed with food, irritable, and depressed. Many developed eating disorder behaviors that persisted for years.

The experiment is now a foundational reference in eating disorder research and metabolic adaptation literature.

Why am I bringing this up?

Because GLP-1 drugs work by producing a caloric deficit. A large one. Trial data on semaglutide shows participants typically eat 30–35% fewer calories. That doesn’t put you in a starvation state, but it does mean your body is responding to a sustained, significant energy deficit, which triggers many of the same compensatory mechanisms Keys and his team documented:

• Lowered metabolic rate

• Loss of lean tissue

• Hormonal shifts

• Increased food preoccupation when the drug wears off

The drug doesn’t override biology. It quiets the hunger signals. The biology underneath keeps doing what biology does.

What the muscle data actually says

This is the part most prescriptions skip.

In the STEP 1 trial, the pivotal study for semaglutide as a weight loss drug, participants lost an average of 15.3 kg (about 33 lb) over 68 weeks. Of that, roughly 6.92 kg was lean body mass. That’s about 45% of total weight lost.

In the SURMOUNT-1 trial of tirzepatide, participants lost about 22 kg, with roughly 26–34% coming from lean mass. With liraglutide, some studies show lean mass loss climbing to 60% of total weight lost.

To put that in context: nutrition science generally accepts a “quarter rule”, about 25% of weight lost in a typical fat-loss phase comes from lean tissue. GLP-1 drugs, in many cases, blow past that significantly.

Lean mass isn’t just “muscles for the gym.” It’s:

• Skeletal muscle (your strength, posture, mobility)

• Organ tissue (liver, kidneys, heart)

• Bone-supporting tissue

• Your metabolic engine, the tissue that burns calories at rest

Losing lean mass isn’t just about looking smaller; it also means burning fewer calories at rest, losing strength and becoming more susceptible to falls and frailty as you age. Furthermore, your body becomes more efficient at storing fat the moment your calorie intake returns to normal.

This is how people end up smaller in the mirror but worse off metabolically than they started.

A specific concern for women, especially after menopause

Here’s where I want to pay particular attention, because most of the questions I’m getting are from women, and the prescribing conversation rarely adjusts for biology.

Two facts to start with:

1. The major obesity trials for these drugs (STEP, SURMOUNT) were 74–77% female. The drug effects we’re discussing are largely the female effects.

2. Women’s biology responds differently to caloric restriction at different life stages, and after menopause, the math changes significantly.

Here’s what happens to a healthy postmenopausal woman, before any drug enters the picture: estrogen declines, and bone mineral density drops at a rate of roughly 1–2% per year for several years following menopause. Lean muscle mass also declines naturally with age (a process called sarcopenia), and the rate accelerates without resistance training.

Now layer a sustained caloric deficit on top of that.

In the TEMPO Diet trial (Australia), a randomized clinical trial of 101 postmenopausal women with obesity, those who underwent severe energy restriction lost approximately 2.5 times more total hip bone mineral density than those on moderate restriction. The conclusion of the researchers was direct: caution is warranted when implementing aggressive caloric deficits in postmenopausal women, particularly those with osteopenia or osteoporosis.

Now layer a GLP-1 drug specifically.

In Hansen et al. (2024), a randomized, double-blinded, two-centre, phase 2 trial conducted in Denmark and published in the Lancet’s eClinicalMedicine, researchers studied once-weekly semaglutide versus placebo in 64 adults with increased fracture risk. Eighty-six per cent of participants were postmenopausal women. Bone outcomes were the primary endpoint. After 52 weeks:

• Hip bone mineral density decreased by approximately 2.6% with semaglutide

• Lumbar spine bone mineral density decreased by approximately 2.1%

• Markers of bone resorption increased

In other words, semaglutide added another 2.6% hip BMD loss on top of the 1–2% per year a postmenopausal woman is already losing. Compound that over two or three years of treatment, factor in the lean muscle loss happening in parallel, and you have a recipe for accelerated osteoporosis and sarcopenia in exactly the population that can least afford either one.

The FDA labelling for semaglutide notes the possibility of increased fracture risk in older adults and women. Most prescribing conversations do not include this. Most patients are not getting baseline DEXA scans before starting therapy. Many never get one during therapy, either.

The combination matters more than either piece alone:

• Less muscle means less mechanical loading on bones, which accelerates further bone loss.

• Less bone density plus less muscle strength means much higher fall and fracture risk, and hip fractures in older women carry a one-year mortality rate of roughly 20–30%.

• Estrogen-deficient bone doesn’t recover the way pre-menopausal bone does, even after refeeding or weight regain.

I’m not telling you that no postmenopausal woman should ever be on a GLP-1. I am telling you that “let’s start you on Wegovy” without DEXA screening, without a serious resistance training plan, without a high-protein nutrition framework, and without an honest conversation about long-term skeletal trade-offs is a prescribing pattern that should make all of us uncomfortable.

If you’re a woman in this stage of life and your doctor offered you a GLP-1 without addressing any of the above, that’s worth a conversation. Not a fight, a conversation.

What the gut is trying to tell you

The most common side effects of GLP-1 drugs are gastrointestinal: nausea, vomiting, diarrhea, constipation, and abdominal pain. In real-world reporting, gastrointestinal side effects affect somewhere between 30% and 80% of patients, depending on the drug and dose. Constipation alone shows up in roughly 8–15% of users in trials and higher in real-world data.

Why? Because the drug deliberately slows down gastric motility. Food sits in your stomach longer. Things move through your gut more slowly.

This isn’t a minor inconvenience. Your gut isn’t just a tube, it’s an ecosystem. The microbiome shifts based on what comes through and how often. When transit slows dramatically, you change the environment your gut bacteria live in, and you change the signals that environment sends back to your brain, your immune system, and your metabolism.

In more serious cases, increasingly documented in the literature, GLP-1 drugs have been linked to gastroparesis (paralysis of stomach motility), bowel obstruction, and pancreatitis. The FDA updated semaglutide labelling in 2023 to reflect ileus and intestinal obstruction risks.

I’m not telling you the gut issues are inevitable. I’m telling you that “feeling less hungry” and “your digestive system is operating at a fraction of its normal speed” are the same phenomenon. You don’t get one without the other.

The signals regulators are still watching

Both the EMA and the FDA have flagged signals worth knowing about, even where reviews concluded no immediate label changes were warranted.

In July 2023, the European Medicines Agency’s Pharmacovigilance Risk Assessment Committee (PRAC) opened a formal safety review into reports of suicidal ideation and self-harm linked to liraglutide and semaglutide. The review concluded in April 2024 with no causal association established and no update to the product information, but the committee explicitly noted that monitoring would continue, and a separate analysis of the EudraVigilance European pharmacovigilance database identified 230 reports of suicidal events across GLP-1 RAs over five years.

The signal isn’t a verdict. It’s a watch list. It’s also a reminder that “approved” doesn’t mean “fully understood.” These molecules have only been studied in non-diabetic obesity populations at scale for a few years. The real-world data is still arriving.

Other ongoing concerns under post-market surveillance include thyroid C-cell tumours (carries a black-box warning in the US based on rodent data; less prominent in EU labelling but monitored), pancreatitis, gallbladder disease, and the gastric emptying issues already covered.

None of this should panic you. All of it should inform a real conversation before you start.

The part nobody mentions: what happens when you stop

Here’s the question almost no one asks at the prescription stage: what happens when you come off the drug?

The STEP 1 trial extension followed participants for one year after they stopped semaglutide. The result: they regained roughly two-thirds of the weight they had lost. Cardiometabolic markers, blood pressure, lipids, and blood sugar drifted back toward baseline.

The STEP 4 trial showed something similar: continue the drug, keep losing weight; switch to placebo, gain it back.

Translation: these are not “use them, lose the weight, you’re done” drugs. They’re chronic-use medications. The current scientific consensus, including from the trial sponsors themselves, is that obesity is a chronic disease and ongoing pharmacotherapy is required to maintain results.

That changes the math. You’re not signing up for “a year on a GLP-1.” You’re signing up for indefinite use, indefinite cost, indefinite side effects, and the possibility that you’ve lost a chunk of muscle and bone along the way that won’t come back without serious resistance training and protein intake, neither of which most prescriptions come with.

The reframe: foundations first

Here’s where I want to be careful and clear.

I’m not anti-medication. For someone with type 2 diabetes whose glycemic control is failing, or someone with severe obesity and significant comorbidity, GLP-1 drugs can be genuinely life-changing. That’s the population they were originally studied in. That’s where the risk-benefit math makes sense.

What I’m pushing back on is the day-one prescription for someone whose nutrition, sleep, movement, and stress have never been properly addressed. The doctor who hands over a pen before asking how you eat, how you sleep, or whether you’ve ever lifted anything heavier than your phone is skipping a step that the drug was never designed to replace.

In Precision Nutrition, we use a framework I find myself coming back to in every coaching conversation: dials, not switches. Health behaviors aren’t on/off. They’re calibrated.

Before the pen, here’s what the dials look like:

• Protein. One to two palms per meal, three meals a day. Adequate protein is the single most powerful nutritional lever for preserving lean mass and supporting bone during any kind of weight loss, and the lever that becomes more important, not less, after menopause.

• Plate structure. Two fists of vegetables, one to two cupped handfuls of quality carbs, one to two thumbs of healthy fats per meal. The PN hand portion guide does more for portion control than most apps will.

• Eating to 80% full. Slowing down, paying attention, and stopping before you’re stuffed is, pharmacologically speaking, what GLP-1 drugs do for you. You can train this. It’s a skill.

• Sleep. Seven to nine hours. Sleep deprivation alone increases hunger and shifts food choices toward calorie-dense, low-nutrient options. No drug fixes this.

• Strength training. Two to four sessions a week. This is your insurance policy on lean mass and bone density, drug or no drug, and especially after age 40.

• Hydration and electrolytes. Most people drift through life mildly dehydrated and read it as hunger. Address this before you address anything else.

None of this is glamorous. None of it sells €1,000+/month subscriptions. And all of it has decades of evidence behind it.

Key takeaways

1. GLP-1 drugs were designed for type 2 diabetes, not obesity. The weight loss indication is a higher-dose repurposing of FDA-approved Wegovy in 2021, EMA in January 2022. Long-term safety data in non-diabetic populations is still catching up.

2. They work by producing a sustained caloric deficit through enhanced satiety and slowed gastric emptying. They don’t override biology, they quiet the signals while biology keeps responding underneath.

3. Lean mass loss is significant. In the major trials, 25–60% of total weight lost came from lean tissue. Without intentional protein intake and resistance training, you lose muscle, not just fat.

4. Postmenopausal women face compounded risk. On top of natural age-related bone and muscle loss, GLP-1 therapy adds measurable bone density loss (Hansen et al. 2024 documented 2.6% hip BMD loss in 52 weeks) and accelerates sarcopenia. DEXA screening, resistance training, and high-protein nutrition aren’t optional in this population, they’re the standard of care.

5. GI side effects are the rule, not the exception. Constipation, nausea, slowed gastric emptying, and, in some cases, more serious complications. Your gut is paying for the appetite suppression.

6. Regulators are still watching. EMA’s PRAC reviewed suicidality signals through 2024. Thyroid, pancreatitis, and gallbladder concerns remain under post-market surveillance. “Approved” is not “fully understood.”

7. Weight regain after stopping is the norm. Roughly two-thirds of lost weight returns within a year of discontinuation. These are chronic-use drugs, not short-term fixes.

8. Foundations first, drugs second. Protein, plate structure, sleep, strength training, and hydration. These aren’t “instead of” medication for everyone, but they should always be tried first, optimized properly, and continued with the medication for anyone who genuinely needs it.

Over to you

I’d genuinely like to hear from you on this one.

If you’re on a GLP-1, particularly if you’re a woman, and especially if you’re peri- or post-menopausal, what did your doctor explain to you before starting? Were bone density and lean mass part of the conversation? What’s your experience been, both the good and the trade-offs you didn’t expect?

If you’ve considered one and decided against it, what tipped the scales?

And if you’re a clinician reading this, I’m not interested in a fight. I’m interested in why the foundational conversation is being skipped so often, and why women in particular are being prescribed without screening that ought to be routine. What’s getting in the way?

Drop a comment. Let’s actually talk about this.

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If you want help building the foundations before considering medication, or alongside it, that’s exactly what I do. The Pro Nutrition Blueprint and the Lifelong Habit System are built around the principles above: protein-led plates, sustainable habits, lean mass preservation, and the long game.

Truth over trends. Always.

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References

1. Wilding JPH, Batterham RL, Calanna S, et al. Once-weekly semaglutide in adults with overweight or obesity. N Engl J Med. 2021;384(11):989-1002. (STEP 1)

2. Wilding JPH, Batterham RL, Davies M, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes Obes Metab. 2022;24(8):1553-1564.

3. Rubino D, Abrahamsson N, Davies M, et al. Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance in adults with overweight or obesity: The STEP 4 randomized clinical trial. JAMA.2021;325(14):1414-1425.

4. Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med.2022;387(3):205-216. (SURMOUNT-1)

5. Hansen MS, Wölfel EM, Jeromdesella S, et al. Once-weekly semaglutide versus placebo in adults with increased fracture risk: a randomised, double-blinded, two-centre, phase 2 trial. eClinicalMedicine. 2024;72:102624. (Denmark)

6. Seimon RV, Wild-Taylor AL, Keating SE, et al. Effect of weight loss via severe vs moderate energy restriction on lean mass and body composition among postmenopausal women with obesity: The TEMPO Diet randomized clinical trial. JAMA Netw Open. 2019;2(10):e1913733.

7. Neeland IJ, Linge J, Birkenfeld AL. Changes in lean body mass with glucagon-like peptide-1-based therapies and mitigation strategies. Diabetes Obes Metab. 2024;26(Suppl 4):16-27.

8. Prado CM, Phillips SM, Gonzalez MC, Heymsfield SB. Muscle matters: the effects of medically induced weight loss on skeletal muscle. Lancet Diabetes Endocrinol. 2024;12(11):785-787.

9. European Medicines Agency. Wegovy: European Public Assessment Report. Available at: https://www.ema.europa.eu/en/medicines/human/EPAR/wegovy

10. European Medicines Agency. PRAC meeting highlights, 8–11 April 2024: Outcome of GLP-1 receptor agonists suicidal ideation review.

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14. Camilleri M, Acosta A. Clinical consequences of delayed gastric emptying with GLP-1 receptor agonists and tirzepatide. J Clin Endocrinol Metab. 2024 Dec.

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