Pharmaceutical treatment of obesity has changed the landscape of healthcare drastically. Within a remarkably short period, drugs such as semaglutide have moved from specialist diabetes clinics into everyday conversation, while the extraordinary commercial and cultural success of these medicines has made GLP-1 one of the most recognisable acronyms in health.

It would be easy to assume that this represents the culmination of obesity pharmacology. In reality, it increasingly looks like the opening chapter.

The next generation of treatments is already moving beyond GLP-1 alone. Tirzepatide simultaneously targets receptors for GLP-1 and GIP. Retatrutide adds glucagon to create a triple-receptor agonist. Survodutide combines GLP-1 and glucagon signalling. Cagrilintide and petrelintide target amylin, another hormone involved in the physiological response to eating. Other drugs are being designed to manipulate several metabolic signals simultaneously, sometimes in combinations that would have seemed distinctly counterintuitive only a decade ago.

What makes this particularly interesting is not simply that some of these drugs are producing greater weight loss. Their development is revealing just how complicated the biological regulation of appetite and body weight really is. Hunger, satiation, gastric emptying, insulin secretion, glucose regulation, nutrient sensing, reward and energy expenditure emerge from an interconnected network involving the gastrointestinal tract, pancreas, liver, adipose tissue and brain. GLP-1 receptor agonists demonstrated that pharmacologically altering one part of this system can have profound effects on eating behaviour and body weight. The new generation of drugs is exploring what happens when several parts of that network are manipulated at the same time.

The results are already substantial enough to change the discussion around obesity treatment. They also raise a question that has received considerably less attention than the headline weight-loss figures. If medicines can help somebody lose 15%, 20% or potentially even more of their starting body weight, we need to become increasingly interested in the quality of that weight loss. Preserving skeletal muscle, maintaining nutritional adequacy, supporting gastrointestinal health and building a dietary pattern that can coexist with dramatically reduced appetite may become just as important as making the number on the scales smaller.

GLP-1 was never simply a weight-loss hormone

Glucagon-like peptide-1, or GLP-1, is produced predominantly by specialised enteroendocrine L-cells within the intestine in response to nutrient exposure. Its normal physiological role extends considerably beyond appetite.

GLP-1 is one of the principal incretin hormones. When glucose is consumed orally, the insulin response is considerably greater than when an equivalent glucose load is delivered directly into the circulation. This phenomenon, known as the incretin effect, occurs partly because nutrient exposure within the gastrointestinal tract stimulates hormones including GLP-1 and glucose-dependent insulinotropic polypeptide, or GIP. These hormones essentially allow the gut to tell the pancreas that nutrients are arriving.

GLP-1 enhances insulin secretion when glucose concentrations are elevated and can suppress inappropriate glucagon secretion. It also slows gastric emptying and communicates with neural systems involved in satiation and appetite regulation. These actions make physiological sense when considered together. Food enters the digestive system, nutrient-responsive hormones are released, the pancreas prepares to deal with incoming glucose, movement of food through the stomach is regulated and the brain receives information contributing to the termination of the meal.

Naturally occurring GLP-1 has an extremely short active life because it is rapidly degraded by the enzyme dipeptidyl peptidase-4, or DPP-4. Pharmaceutical GLP-1 receptor agonists were therefore designed to resist this rapid degradation and produce much more sustained receptor activation.

Semaglutide demonstrated just how powerful that strategy could become. In the landmark STEP 1 randomised controlled trial, 1,961 adults with overweight or obesity but without diabetes received either once-weekly semaglutide 2.4 mg or placebo alongside lifestyle intervention. After 68 weeks, average body weight had fallen by 14.9% in the semaglutide group compared with 2.4% with placebo (Wilding et al., 2021).

For pharmacological obesity treatment, this represented an enormous advance. Previous medicines had generally produced much more modest reductions in body weight, whereas semaglutide began approaching territory previously associated much more closely with bariatric surgery.

It also demonstrated something else. Manipulating the hormonal regulation of appetite could produce changes in eating behaviour substantial enough to alter body weight on a scale that traditional advice to simply exert more restraint had rarely achieved.

Adding GIP changed the picture again

GIP is another incretin hormone released predominantly from K-cells in the upper small intestine following nutrient ingestion. Like GLP-1, it enhances glucose-dependent insulin secretion, but its biology extends across multiple tissues, including adipose tissue and the central nervous system.

For many years, targeting GIP as a treatment for obesity was far from an obvious strategy. Its involvement in nutrient storage and adipose biology led some researchers to investigate whether blocking GIP signalling might be beneficial. The arrival of tirzepatide complicated that picture considerably.

Tirzepatide is a single molecule capable of activating both GIP and GLP-1 receptors. In the SURMOUNT-1 trial, 2,539 adults with overweight or obesity but without diabetes were randomly assigned to receive tirzepatide at one of three doses or placebo for 72 weeks. Average weight loss reached 20.9% with the highest 15 mg dose, compared with 3.1% with placebo. More than half of participants receiving the 10 mg or 15 mg doses lost at least 20% of their starting body weight (Jastreboff et al., 2022).

Those results changed expectations again. Semaglutide had demonstrated that amplifying GLP-1 signalling could produce substantial weight loss, while tirzepatide suggested that deliberately combining hormonal pathways could push the effect further.

Precisely why GIP receptor agonism adds so much to GLP-1 receptor agonism remains an active area of research. Both receptors are involved in glucose regulation and are expressed within neural systems influencing energy balance, but their actions are not identical. Simultaneous activation may produce complementary effects on appetite and metabolic regulation, while GIP activity may also influence the tolerability and overall effectiveness of combined incretin signalling.

This is an important reminder that successful pharmacology does not always wait for physiology to provide a perfectly tidy explanation. Occasionally a treatment demonstrates that our existing model was incomplete, forcing the biology to catch up afterwards.

Then researchers added glucagon

If combining GLP-1 and GIP initially appeared counterintuitive, adding glucagon sounds stranger still.

Most introductory physiology presents glucagon as insulin's counter-regulatory partner. When circulating glucose begins to fall, glucagon released from pancreatic alpha cells acts predominantly on the liver, stimulating glycogen breakdown and gluconeogenesis and helping to restore blood glucose concentrations. Deliberately activating the glucagon receptor in somebody with obesity, insulin resistance or type 2 diabetes therefore appears, at first glance, to be heading in precisely the wrong direction.

Glucagon, however, does considerably more than increase hepatic glucose output. Its signalling influences lipid metabolism, amino-acid metabolism, hepatic energy expenditure and food intake. Researchers have therefore become interested in whether some of these effects could be therapeutically useful if glucagon activity were combined with incretin signalling capable of counterbalancing its potential glucose-raising effects.

This is where retatrutide becomes particularly interesting.

Retatrutide is a single molecule that activates receptors for GIP, GLP-1 and glucagon. Rather than simply amplifying satiation through GLP-1, it attempts to coordinate three metabolic signals simultaneously.

In a phase II randomised trial involving 338 adults with obesity, participants receiving the highest 12 mg dose lost an average of 24.2% of their body weight after 48 weeks, compared with 2.1% with placebo (Jastreboff et al., 2023). Perhaps most strikingly, the weight-loss curve had not clearly plateaued when the trial ended.

Results of that magnitude inevitably generate headlines, but the physiology is arguably more important than the percentage. Retatrutide provides proof of principle that glucagon receptor activation can be incorporated into an obesity therapy rather than automatically working against it. The glucose-raising potential of glucagon appears capable of being balanced by simultaneous incretin activity while other metabolic actions may contribute to the overall effect.

This does not mean that glucagon has suddenly become a weight-loss hormone. It means that hormones cannot always be understood by assigning each of them a single metabolic job. Human physiology is a network, and the consequence of activating one pathway depends partly upon what is happening elsewhere in that network.

Survodutide gives us another way of testing the glucagon idea

Survodutide takes a slightly different approach by combining GLP-1 and glucagon receptor agonism without GIP.

This provides another test of the hypothesis that glucagon activity can contribute usefully to obesity treatment when balanced by GLP-1 signalling. Recent phase III results have strengthened the evidence that this dual approach can produce clinically meaningful weight loss and improvements in glycaemic control.

In SYNCHRONIZE-2, adults with overweight or obesity and type 2 diabetes were treated for 76 weeks. Using the treatment-regimen estimand, average body weight fell by 8.2% with 3.6 mg survodutide and 9.8% with 6 mg, compared with 3.9% with placebo. HbA1c also fell by approximately 0.8–0.9 percentage points with active treatment.

Those weight-loss figures are less spectacular than the highest numbers reported with retatrutide or tirzepatide, although direct comparisons between separate trials are fraught with problems. People with type 2 diabetes typically lose less weight in pharmacological obesity trials than people without diabetes, and differences in study design, treatment duration, statistical analysis and participant characteristics make simple rankings misleading.

Survodutide is also of particular interest because glucagon receptor agonism may have effects on hepatic metabolism that could prove useful in people with metabolic liver disease. Whether this ultimately translates into advantages beyond weight loss will require outcome data rather than mechanistic enthusiasm.

Tolerability remains another consideration. Gastrointestinal adverse effects were common in SYNCHRONIZE-2, occurring in approximately three quarters of participants receiving survodutide. This is a recurring theme across incretin-based therapies and an important counterweight to the tendency to judge obesity medicines solely according to the maximum weight loss they produce.

A medicine that produces enormous average weight loss but which a substantial proportion of people cannot comfortably continue is not automatically superior to one producing a slightly smaller effect with better long-term tolerability.

Amylin takes obesity pharmacology in another direction

The next generation of treatments is not limited to increasingly elaborate combinations of incretin receptors. Amylin offers an entirely different route into the physiology of satiation.

Amylin is produced by pancreatic beta cells and released alongside insulin after eating. It participates in postprandial glucose regulation, slows gastric emptying and sends satiation signals to the brain. A synthetic amylin analogue, pramlintide, has been used in diabetes treatment for years, but newer molecules have been engineered specifically with obesity treatment in mind.

Cagrilintide is a long-acting amylin analogue that has been combined with semaglutide in a treatment known as CagriSema. This pairing is physiologically interesting because it combines an intestinal incretin signal with a pancreatic hormone normally released alongside insulin after food enters the system.

Phase III trials have shown substantial weight reduction with the combination. In REDEFINE 1, adults with overweight or obesity but without diabetes receiving CagriSema achieved weight reductions approaching 20% over 68 weeks, while REDEFINE 2 demonstrated substantial weight loss and improvements in glycaemic control among people with type 2 diabetes.

Once again, gastrointestinal adverse effects remain common, and the eventual place of CagriSema in clinical practice will depend upon considerably more than its average weight-loss percentage. Nevertheless, the results support the broader idea that the physiology of obesity treatment can be approached through several complementary hormonal systems rather than increasingly aggressive stimulation of GLP-1 alone.

Could amylin eventually offer an alternative to GLP-1?

Petrelintide makes this question particularly interesting.

Petrelintide is another long-acting amylin analogue, but unlike CagriSema it is being developed as a potential standalone obesity treatment. Phase II ZUPREME-1 results have reported mean weight loss approaching 11% after 42 weeks at the most effective doses, compared with less than 2% with placebo.

The reported tolerability profile has also attracted attention, particularly the relatively low levels of nausea and vomiting compared with what has become familiar from incretin therapies. Those findings need confirmation in larger phase III programmes and should be interpreted cautiously while much of the available information remains sponsor-reported. Nevertheless, they raise the possibility that future obesity treatment may involve choosing between hormonal pathways according to individual needs rather than simply escalating towards whichever medicine produces the greatest average weight loss.

That would represent a considerably more mature therapeutic landscape. Some people may need very substantial reductions in adiposity because of severe metabolic disease. Others may benefit more from moderate weight loss with excellent tolerability. Individual priorities may include diabetes control, cardiovascular disease, fatty liver disease, preservation of muscle or simply finding a treatment they can realistically continue.

Obesity is heterogeneous. There is little reason to assume that its pharmacological treatment will ultimately converge on one ideal drug for everybody.

The biggest percentage does not necessarily identify the best treatment

The extraordinary results emerging from obesity trials make it tempting to construct a league table. Semaglutide produces one percentage, tirzepatide another and retatrutide apparently pushes the figure higher still. It makes for an excellent graphic, but not necessarily excellent medicine.

These numbers frequently come from entirely different trials. Participants differ in age, baseline body weight, diabetes status and disease burden. Treatment periods differ. Dose-escalation schedules differ. Some studies report treatment-policy estimands that include people who discontinue treatment, while others emphasise efficacy estimands designed to estimate what happens when treatment is taken as intended.

Direct head-to-head trials provide much stronger comparisons than placing separate studies next to one another and declaring a winner.

There is also a more fundamental problem with focusing exclusively on total weight loss. A 20% reduction in body weight is unquestionably clinically important for many people living with obesity, particularly when accompanied by improvements in glycaemia, blood pressure, liver fat, mobility or cardiovascular risk. However, body weight tells us nothing about the composition of the tissue being lost.

As these medicines become increasingly powerful, that distinction becomes increasingly important.

Weight loss is not synonymous with fat loss

When somebody loses a substantial amount of body weight, not all of that loss comes from adipose tissue. Fat-free mass also falls.

This occurs during dietary energy restriction and following bariatric surgery as well as during pharmacological weight loss. It is therefore misleading to suggest that GLP-1 receptor agonists uniquely “eat muscle”, as some recent commentary has implied.

There is another complication. Measurements of lean mass are not measurements of skeletal muscle alone. DXA-derived lean mass includes body water, organs and other non-fat tissues, while rapid changes in glycogen and associated water can influence estimates during substantial weight loss.

Nevertheless, loss of skeletal muscle during major weight reduction is clinically relevant, particularly for older adults or people beginning treatment with poor muscle reserves.

A recent systematic review and meta-analysis examining randomised controlled trials of semaglutide and tirzepatide estimated that lean tissue represented a meaningful proportion of the total weight lost. The proportion varied between drugs and studies and was broadly comparable with that seen during lifestyle-induced weight loss. Importantly, lifestyle interventions incorporating resistance exercise appeared to preserve lean tissue considerably more effectively.

This changes the question from whether GLP-1 drugs uniquely cause muscle loss to something far more useful: how do we preserve skeletal muscle whenever substantial weight loss occurs?

Why muscle preservation matters

Skeletal muscle is often treated as an aesthetic concern, particularly in discussions about weight loss. Physiologically, it is much more important.

Muscle is a major site of glucose disposal and plays a central role in insulin sensitivity. It acts as a reservoir of amino acids during illness and physiological stress and contributes enormously to mobility, balance, strength and functional independence. As we age, the amount of muscle we possess becomes only part of the picture; strength and power become increasingly important determinants of whether that tissue can actually perform useful work.

This becomes especially relevant as obesity treatment increasingly reaches older populations. Excess adiposity and poor skeletal-muscle function can coexist, producing the particularly undesirable combination often described as sarcopenic obesity. In this situation, aggressive weight reduction without adequate attention to muscle could theoretically improve one component of health while weakening another.

None of this argues against treating obesity. Substantial fat loss can produce enormous benefits for people with metabolic disease. It argues for treating obesity intelligently, with body composition and physical function considered alongside the scales.

The more effective our weight-loss therapies become, the less excusable it becomes to ignore what happens to muscle during treatment.

Resistance training deserves a much bigger role

Resistance exercise provides one of the strongest available physiological signals for retaining skeletal muscle during weight loss.

Energy restriction creates an environment in which the body has less reason to maintain energetically expensive tissue. Mechanical loading gives muscle a reason to remain. Resistance exercise stimulates muscle-protein synthesis and promotes adaptations in strength and function, while dietary protein supplies the amino acids required to support that process.

Evidence from weight-loss interventions more broadly consistently suggests that resistance training can attenuate the loss of lean tissue during energy restriction. Specific evidence defining the optimal resistance-training prescription alongside the newest incretin and polyagonist medicines is still developing, so it would be premature to pretend we know the perfect programme.

The general principle, however, is difficult to argue with. If somebody is deliberately losing a very large amount of body mass, particularly later in life, maintaining a regular stimulus that tells skeletal muscle it is still required makes considerably more sense than waiting until significant strength has been lost and trying to rebuild it afterwards.

As pharmacological obesity treatment matures, I suspect resistance training will increasingly become viewed as part of good clinical management rather than an optional lifestyle extra.

Reduced appetite creates a nutritional paradox

The same drugs that make substantial weight loss possible can also make adequate nutrition more challenging.

This is an inevitable consequence of effective appetite suppression. If somebody who previously consumed 2,500 calories per day begins comfortably eating 1,500 because hunger and food preoccupation have fallen dramatically, they now have considerably less food through which to obtain protein, fibre, essential fatty acids, vitamins and minerals.

The answer is not to force food intake back upwards until the medication's effect has effectively been defeated. It is to improve the nutritional quality of what remains.

Protein becomes particularly important because energy restriction and weight loss create conditions in which lean tissue may be lost. Requirements vary according to age, body size, physical activity, kidney function, total energy intake and baseline muscle status, so there is no sensible universal protein prescription for everybody using these medicines. What is reasonable is ensuring that protein-rich foods are deliberately represented within the smaller amount of food being eaten.

For an omnivorous diet this may include fish, eggs, dairy foods, poultry and lean meat. Plant-based diets can achieve the same objective using foods such as tofu, tempeh, legumes, soya products and, where useful, supplementary protein. The purpose is not to transform obesity treatment into bodybuilding nutrition but to prevent successful appetite suppression from inadvertently producing an unnecessarily poor environment for muscle maintenance.

Micronutrient density matters for exactly the same reason

A dramatic reduction in food intake also reduces opportunities to obtain vitamins and minerals.

Someone consuming substantially smaller meals still requires iron, zinc, calcium, folate, vitamin B12, vitamin D, iodine and the many other micronutrients required for normal physiology. Whether deficiencies actually develop will depend upon the quality of the person's baseline diet, the extent of appetite suppression, gastrointestinal symptoms and individual circumstances.

Routine high-dose supplementation for everybody using an obesity drug would therefore make little sense. A person eating a varied, nutrient-dense diet has very different needs from somebody living on tiny portions of nutritionally poor convenience food because nothing else appeals to them.

This is where nutritional assessment becomes increasingly valuable. As total food intake decreases, nutrient density becomes more important rather than less. Vegetables, fruit, legumes, whole grains, nuts, seeds and high-quality protein sources can deliver considerably more nutritional value per mouthful than foods contributing large amounts of energy with relatively little else.

The arrival of effective obesity drugs has not made healthy eating redundant. It has made wasting somebody's reduced appetite on nutritionally poor food considerably harder to justify.

Fibre and gastrointestinal health require a little more finesse

Gastrointestinal symptoms are among the most common adverse effects of GLP-1-based medicines, with nausea, constipation, diarrhoea and early fullness frequently reported. Reduced food intake itself can also reduce fibre consumption, potentially worsening constipation.

Simply telling everybody to consume enormous amounts of fibre is not necessarily helpful. A person already experiencing marked early satiety and delayed gastric emptying may feel considerably worse after suddenly adding large quantities of bulky fibre or supplements.

Fibre intake therefore needs to be considered alongside tolerance, fluid intake and the person's overall gastrointestinal response. Fruit, vegetables, legumes, oats, whole grains, nuts and seeds can provide fibre together with micronutrients and phytochemicals, making them particularly useful when total food intake is limited. Some people may benefit from gradually increasing particular fibre sources rather than attempting to reach an arbitrary target overnight.

This is another example of why nutrition alongside obesity pharmacotherapy needs to become more individualised. The correct diet is not simply “eat less”. The medication has already become extremely good at achieving that.

These drugs have changed what we understand about appetite

Perhaps one of the most important consequences of incretin pharmacology is that it has made the biological regulation of appetite extremely difficult to ignore.

For decades, people living with obesity have often been told that successful weight management ultimately comes down to discipline. Eat less, move more and maintain sufficient willpower to continue doing so indefinitely. Energy balance is undeniably fundamental to changes in body mass, but that statement says very little about the biological forces influencing how easy or difficult it is for an individual to sustain the behaviours that create that energy balance.

The experience reported by many people taking GLP-1-based medicines illustrates this beautifully. Persistent hunger can diminish, satiation can arrive much earlier during a meal and thoughts about food that previously occupied a substantial amount of mental space can become considerably quieter. These changes can occur without somebody acquiring a new personality, discovering previously hidden reserves of discipline or suddenly receiving nutritional information they had somehow missed for the preceding twenty years. Pharmacologically altering nutrient-responsive signalling changes the biological environment in which eating behaviour occurs.

That does not invalidate energy balance. Quite the opposite: it helps explain one of the mechanisms through which energy intake can be changed so dramatically. GLP-1, GIP, glucagon and amylin operate alongside leptin, ghrelin, insulin, hypothalamic nutrient sensing, reward circuitry, genetics, sleep, stress, physical activity and the surrounding food environment. Body-weight regulation emerges from the interaction between these systems rather than from one hormone or one behavioural decision.

The success of obesity pharmacotherapy should therefore make the old argument about willpower considerably less attractive. If manipulating a handful of receptors can profoundly alter hunger and spontaneous food intake, then appetite was clearly never just a matter of character.

What happens when treatment stops?

One of the most important unresolved practical issues is long-term treatment.

When GLP-1-based therapy is withdrawn, appetite-regulating effects diminish and substantial weight regain commonly occurs. In the STEP 1 extension, participants regained approximately two-thirds of their previous weight loss during the year after semaglutide was withdrawn, alongside movement of several cardiometabolic measures back towards baseline (Wilding et al., 2022).

This is sometimes presented as evidence that the drugs do not work, but that interpretation is peculiar. We do not generally conclude that an antihypertensive has failed because blood pressure rises when treatment stops.

Obesity is increasingly understood as a chronic, relapsing disease in which biological adaptations strongly defend body weight following weight loss. Long-term pharmacotherapy may therefore be appropriate for many people, just as long-term treatment is accepted for hypertension, dyslipidaemia and type 2 diabetes.

However, lifelong treatment introduces questions around cost, access, adherence, tolerability, pregnancy, ageing and changing health status. Some people will also choose to discontinue medication.

This makes the period during successful treatment enormously valuable. If appetite is temporarily much easier to manage, that provides an opportunity to establish a dietary pattern capable of supporting long-term health, develop resistance-training habits, improve cardiorespiratory fitness and address the wider metabolic risk factors that brought somebody to treatment in the first place.

None of those behaviours guarantees that weight will remain stable after medication is withdrawn. The biological pressures driving weight regain do not disappear simply because somebody has learnt to cook lentils and perform a decent squat. They do, however, leave the individual in a considerably better physiological position than weight loss alone.

The future may be about better weight loss rather than simply more weight loss

Obesity pharmacology is developing at an extraordinary pace. GLP-1 receptor agonism has already been joined by GLP-1/GIP dual agonism, GLP-1/glucagon agonism, triple GLP-1/GIP/glucagon agonism and amylin-based approaches. Other combinations are under development, and future therapies may also incorporate mechanisms specifically intended to preserve skeletal muscle while adipose tissue is lost.

This raises the possibility that treatment may eventually become considerably more personalised. A person with severe obesity and type 2 diabetes may require a different pharmacological profile from somebody with obesity and advanced metabolic liver disease. An older adult at risk of sarcopenia may require a different therapeutic calculation from a younger person with substantial adiposity and excellent muscle reserves. For some people, maximum weight reduction may be the priority; for others, tolerability, body composition or long-term adherence may matter more.

If that happens, the rather crude question of which drug causes the greatest percentage weight loss will begin to look increasingly outdated.

The more useful questions will concern which tissue is being lost, which disease risks are improving, how well the treatment can be tolerated and whether the person becomes metabolically and physically healthier as their body weight falls.

Nutrition becomes more important as the drugs become more effective

There is a temptation to view the success of GLP-1 medicines as evidence that nutrition has somehow been superseded. If a weekly injection can suppress appetite sufficiently to produce 15–20% weight loss, perhaps all the painstaking discussion about dietary quality suddenly becomes rather quaint.

The opposite conclusion makes far more sense.

When appetite is dramatically reduced, every meal has more nutritional work to do. Protein becomes important for supporting muscle maintenance. Resistance training provides the mechanical stimulus needed to preserve strength and function. Fibre and fluid need attention because gastrointestinal symptoms are common. Vitamins, minerals and essential fatty acids still need to come from somewhere, despite the fact that substantially less food may be passing through the system.

At the same time, body weight should not become the sole measure of success simply because modern drugs can change it so impressively. Blood pressure, glycaemic control, liver health, lipid profile, cardiorespiratory fitness, muscle strength, bone health, nutritional status and quality of life all remain important.

The most exciting aspect of the next generation of obesity drugs may therefore not be that they enable us to make people progressively lighter. It may be that they finally give us sufficient control over one of the most difficult components of obesity — persistent biological pressure to eat — that we can focus more effectively on improving everything else.

GLP-1 changed obesity treatment because it demonstrated that human appetite could be pharmacologically altered with clinically transformative consequences. The drugs now following it are showing that GLP-1 represents only one component of a much larger metabolic network.

The challenge for the next decade will not simply be discovering how much further we can push weight loss. It will be learning how to use that increasingly powerful pharmacology to produce healthier bodies rather than merely smaller ones.

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