That question becomes increasingly important as we get older because skeletal muscle is not cosmetic luggage we can casually leave behind. Muscle contributes to strength, glucose disposal, metabolic health, mobility, bone loading, fall prevention, and our ability to remain independent.<\/p>\n\n\n\n
Enter bimagrumab<\/strong>, an experimental monoclonal antibody that appears to approach obesity from an entirely different direction.<\/p>\n\n\n\n Instead of primarily making you eat less, bimagrumab interferes with biological signals that restrict muscle growth.<\/p>\n\n\n\n And some of the newest human research suggests something rather remarkable.<\/p>\n\n\n\n It may allow people to lose substantial amounts of fat while preserving, or even increasing, lean mass.<\/strong><\/p>\n\n\n\n That could change what successful weight loss means.<\/p>\n\n\n\n (Heymsfield et al., 2021; Heymsfield et al., 2026). (PubMed<\/a>)<\/p>\n\n\n\n Bimagrumab is a fully human monoclonal antibody originally developed to influence skeletal muscle biology.<\/p>\n\n\n\n Its targets are the activin type II receptors<\/strong>, specifically ActRIIA and ActRIIB.<\/p>\n\n\n\n These receptors sit on cell membranes and participate in signaling from several members of the transforming growth factor beta family, including myostatin and activins<\/strong>.<\/p>\n\n\n\n Myostatin is particularly interesting.<\/p>\n\n\n\n Its biological job includes limiting skeletal muscle growth. You can think of the myostatin system as one of the body\u2019s built in governors preventing unlimited muscle hypertrophy.<\/p>\n\n\n\n Myostatin and related ligands bind activin receptors and stimulate downstream SMAD2\/3 signaling. These signals suppress aspects of muscle differentiation and growth. Bimagrumab interferes with that process.<\/p>\n\n\n\n By blocking both ActRIIA and ActRIIB, it prevents several muscle growth suppressing ligands from activating their receptors.<\/p>\n\n\n\n That distinction matters because bimagrumab is not merely a myostatin inhibitor<\/strong>. It interferes with a broader signaling network involving myostatin, activins, and related ligands (Lach-Trifilieff et al., 2014). (PubMed<\/a>)<\/p>\n\n\n\n The simplified pathway looks like this:<\/p>\n\n\n\n Myostatin \/ activin \u2192 ActRIIA \/ ActRIIB \u2192 SMAD2\/3 signaling \u2192 restriction of muscle growth<\/strong><\/p>\n\n\n\n Bimagrumab blocks ActRIIA and ActRIIB.<\/p>\n\n\n\n The result is reduced inhibitory signaling.<\/p>\n\n\n\n The muscle growth brake loosens.<\/p>\n\n\n\n But something unexpected happened during clinical development.<\/p>\n\n\n\n Researchers began noticing that bimagrumab was not simply affecting muscle.<\/p>\n\n\n\n People were losing substantial amounts of fat.<\/strong><\/p>\n\n\n\n One of the most important early clues came from a randomized Phase 2 clinical trial published in JAMA Network Open<\/em>.<\/p>\n\n\n\n Researchers studied 75 adults with type 2 diabetes and overweight or obesity.<\/p>\n\n\n\n After 48 weeks, participants receiving bimagrumab experienced approximately:<\/p>\n\n\n\n Participants receiving bimagrumab lost roughly 7.5 kilograms of fat while gaining approximately 1.7 kilograms of lean tissue<\/strong> (Heymsfield et al., 2021). (PubMed<\/a>)<\/p>\n\n\n\n Stop for a moment and consider what those numbers mean.<\/p>\n\n\n\n Scale weight fell by around 6.5%.<\/p>\n\n\n\n But fat mass fell by more than 20%.<\/p>\n\n\n\n If you looked only at body weight, you would dramatically underestimate the change occurring inside the body.<\/p>\n\n\n\n And this points toward one of the biggest problems with our obsession with scale weight.<\/p>\n\n\n\n Two people can each lose 20 pounds while experiencing completely different physiological transformations.<\/p>\n\n\n\n One could lose mostly adipose tissue while maintaining muscle.<\/p>\n\n\n\n The other could lose considerable muscle along with fat.<\/p>\n\n\n\n The bathroom scale congratulates both of them equally.<\/p>\n\n\n\n Their physiology and older self may widely disagree!<\/p>\n\n\n\n In March 2026, Nature Medicine<\/em><\/a> published the Phase 2 BELIEVE trial.<\/p>\n\n\n\n This study included 507 adults with obesity<\/strong> and compared bimagrumab, semaglutide, various combinations of the two, and placebo.<\/p>\n\n\n\n Bimagrumab was administered intravenously every 12 weeks, while semaglutide was administered weekly.<\/p>\n\n\n\n At 48 weeks, body weight decreased by approximately 9.3 kilograms with high dose bimagrumab, 14.2 kilograms with semaglutide 2.4 mg, and 17.8 kilograms with the high dose combination (Heymsfield et al., 2026). (Nature<\/a>)<\/p>\n\n\n\n If we stopped there, semaglutide would appear to be the obvious winner.<\/p>\n\n\n\n But then researchers looked inside the weight loss.<\/p>\n\n\n\n That is where the story gets much more interesting.<\/p>\n\n\n\n At 72 weeks, the efficacy analysis found that high dose bimagrumab reduced body weight approximately 10.8%<\/strong>, compared with 15.7%<\/strong> for semaglutide and 22.1%<\/strong> for their high dose combination.<\/p>\n\n\n\n Yet fat mass told another story.<\/p>\n\n\n\n Bimagrumab reduced total fat mass 28.5%<\/strong>.<\/p>\n\n\n\n Semaglutide reduced fat mass 27.8%<\/strong>.<\/p>\n\n\n\n The combination reduced fat mass an extraordinary 45.7%<\/strong>.<\/p>\n\n\n\n And then we arrive at lean mass.<\/p>\n\n\n\n Bimagrumab alone produced an approximately 2.5% increase in lean mass<\/strong>.<\/p>\n\n\n\n Semaglutide produced about a 7.4% decrease<\/strong>.<\/p>\n\n\n\n The combination limited lean mass decline to approximately 2.9%<\/strong>, despite producing considerably greater overall weight loss (Heymsfield et al., 2026).<\/p>\n\n\n\n This may ultimately be bimagrumab\u2019s most important contribution.<\/p>\n\n\n\n For decades, weight management has largely revolved around three familiar measurements:<\/p>\n\n\n\n They are useful, but incomplete. The BELIEVE researchers pointed out that during caloric restriction, incretin therapy and bariatric surgery, approximately 25% to 40% of weight lost can consist of lean mass<\/strong> (Heymsfield et al., 2026). (Nature<\/a>)<\/p>\n\n\n\n Some lean tissue reduction is expected during substantial weight loss.<\/p>\n\n\n\n But particularly in older adults, repeatedly losing large amounts of skeletal muscle could carry consequences.<\/p>\n\n\n\n Less muscle can mean reduced strength reserves, lower glucose disposal capacity, poorer physical function and potentially greater vulnerability to sarcopenia later in life.<\/p>\n\n\n\n This does not mean GLP 1 medications inevitably cause pathological muscle wasting. That claim is far too simplistic.<\/p>\n\n\n\n It means body composition deserves to be monitored<\/strong>, particularly during aggressive weight loss.<\/p>\n\n\n\n And it explains why combining an incretin with a drug that protects lean tissue is such an intriguing idea.<\/p>\n\n\n\n The BELIEVE study produced another finding that deserves more attention.<\/p>\n\n\n\n At 72 weeks, estimated visceral adipose tissue decreased approximately:<\/p>\n\n\n\n (Heymsfield et al., 2026).<\/p>\n\n\n\n Visceral adipose tissue is the fat stored deep within the abdominal cavity surrounding internal organs.<\/p>\n\n\n\n Unlike subcutaneous fat sitting underneath the skin, excessive visceral adiposity is closely associated with insulin resistance and cardiometabolic disease.<\/p>\n\n\n\n A therapy capable of simultaneously reducing visceral fat while maintaining skeletal muscle therefore becomes particularly interesting from a metabolic health perspective.<\/p>\n\n\n\n This may eventually matter more than whether someone weighs 184 pounds instead of 189.<\/p>\n\n\n\n Here is where enthusiasm needs some brakes of its own.<\/p>\n\n\n\n Bimagrumab appears much more reliable at increasing muscle size<\/strong> than improving muscle performance<\/strong>.<\/p>\n\n\n\n A randomized study involving adults with COPD and low muscle mass found that bimagrumab increased thigh muscle volume by approximately 5% at 24 weeks.<\/p>\n\n\n\n Yet six minute walking distance did not significantly improve (Polkey et al., 2019). (PubMed<\/a>)<\/p>\n\n\n\n BELIEVE produced a similar caution.<\/p>\n\n\n\n One combination group experienced a significant increase in grip strength, but most treatment groups were not significantly different from placebo. (Nature<\/a>)<\/p>\n\n\n\n This illustrates an important exercise physiology principle:<\/p>\n\n\n\n Muscle mass and muscle function overlap, but they are not identical.<\/strong><\/p>\n\n\n\n Muscle quality also depends upon neural recruitment, mitochondrial function, tendon adaptation, coordination, capillary density, fiber characteristics, movement skill and training.<\/p>\n\n\n\n No antibody can substitute for all of that.<\/p>\n\n\n\n Which leads to something wonderfully old fashioned in an article about futuristic biotechnology.<\/p>\n\n\n\n You still need to train!\u00a0<\/p>\n\n\n\n Even if bimagrumab eventually becomes available, I would not consider it a replacement for resistance exercise.<\/p>\n\n\n\n I would view muscle preserving pharmacology and resistance training as potentially complementary.<\/p>\n\n\n\n Interestingly, participants in BELIEVE received nutritional and activity counseling, including a protein target of at least 1.2 grams per kilogram per day<\/strong> and at least 150 minutes of physical activity per week<\/strong>. (Nature<\/a>)<\/p>\n\n\n\n For someone losing substantial weight, particularly an adult over 40 or 50, I would still prioritize progressive resistance training, adequate dietary protein, sufficient energy and micronutrient intake, adequate sleep and recovery, and creatine monohydrate when appropriate.<\/p>\n\n\n\n Those interventions have something bimagrumab does not yet have.<\/p>\n\n\n\n Decades of real world evidence.<\/p>\n\n\n\n This is worth clarifying because bimagrumab is sometimes discussed in the same internet neighborhoods as peptides and performance enhancing drugs.<\/p>\n\n\n\n Bimagrumab is not a peptide.<\/strong><\/p>\n\n\n\n It is a monoclonal antibody.<\/p>\n\n\n\n It also does not work like testosterone, anabolic steroids, growth hormone or growth hormone secretagogues.<\/p>\n\n\n\n The mechanism is primarily focused on activin receptor signaling.<\/p>\n\n\n\n From a muscle preservation standpoint, creatine remains one of the better supported nutritional additions to resistance exercise, particularly during aging.<\/p>\n\n\n\n Protein adequacy remains foundational.<\/p>\n\n\n\n Hormone replacement should be used for legitimate endocrine indications rather than simply to compensate for poorly managed weight loss.<\/p>\n\n\n\n As for experimental peptides marketed for preserving muscle during GLP 1 therapy, evidence is nowhere near the quality currently available for resistance training, adequate protein and creatine.<\/p>\n\n\n\n The shiny new molecule should never make us forget the boring things that work. Pharmaceuticals can be used as a tool, but lifestyle is the architecture of health.<\/p>\n\n\n\n The activin and myostatin pathway does have an obvious genetic component.<\/p>\n\n\n\n Genes of potential interest include MSTN<\/strong>, which encodes myostatin, ACVR2A<\/strong> and ACVR2B<\/strong>, encoding activin receptors, FST<\/strong>, which encodes follistatin, and downstream signaling genes including SMAD2<\/strong> and SMAD3<\/strong>.<\/p>\n\n\n\n Variants within these systems can influence muscular phenotypes and signaling biology.<\/p>\n\n\n\n But we are not yet at the point where a consumer DNA report can credibly tell someone:<\/p>\n\n\n\n \u201cYou carry this SNP, therefore you should take bimagrumab.\u201d<\/p>\n\n\n\n There is currently no clinically validated pharmacogenomic algorithm for predicting bimagrumab response<\/strong>.<\/p>\n\n\n\n That may change.<\/p>\n\n\n\n For now, genetic information here should be viewed as biologically interesting rather than clinically actionable.<\/p>\n\n\n\n Bimagrumab interferes with a broader signaling system than simply blocking myostatin.<\/p>\n\n\n\n Activin biology participates in numerous physiological processes.<\/p>\n\n\n\n That makes long term safety particularly important.<\/p>\n\n\n\n In BELIEVE, common bimagrumab related adverse events included muscle spasms, diarrhea and acne<\/strong>.<\/p>\n\n\n\n Laboratory findings included changes involving creatine kinase, magnesium, alkaline phosphatase, liver enzymes and lipase. Most adverse events were mild or moderate, but serious adverse events occurred across active treatment groups, and longer observation remains important (Heymsfield et al., 2026). (Nature<\/a>)<\/p>\n\n\n\n The trial investigators also emphasized several limitations.<\/p>\n\n\n\n Lean mass was measured using DXA. DXA does not directly measure skeletal muscle. It measures lean soft tissue, which includes muscle but also other nonfat tissues.<\/p>\n\n\n\n The authors specifically called for future MRI studies to more accurately characterize skeletal muscle quantity and quality. (Nature<\/a>)<\/p>\n\n\n\n That is an important detail before anyone interprets a 2.5% increase in \u201clean mass\u201d as precisely 2.5% more contractile muscle.<\/p>\n\n\n\n Perhaps the most intriguing next step is combining bimagrumab with tirzepatide<\/strong>.<\/p>\n\n\n\n A Phase 2 study involving 252 adults with overweight or obesity has completed enrollment and is examining subcutaneous bimagrumab and tirzepatide individually and together.<\/p>\n\n\n\n The study is expected to run through early 2027.<\/p>\n\n\n\n The question it may help answer is fascinating:<\/p>\n\n\n\n Can an extremely powerful appetite and weight loss drug be combined with activin receptor inhibition to produce large scale fat loss while protecting substantially more muscle?<\/strong><\/p>\n\n\n\n If so, obesity treatment may begin transitioning from a weight loss model toward a body recomposition model<\/strong>.<\/p>\n\n\n\n That would be a significant conceptual change.<\/p>\n\n\n\n Imagine two people each losing 40 pounds.<\/p>\n\n\n\n Person A loses 30 pounds of fat and 10 pounds of lean tissue.<\/p>\n\n\n\n Person B loses 38 pounds of fat and 2 pounds of lean tissue.<\/p>\n\n\n\n The bathroom scale reports the same victory.<\/p>\n\n\n\n Their bodies have experienced very different journeys.<\/p>\n\n\n\n That is why I believe the most interesting aspect of bimagrumab has little to do with producing another blockbuster weight loss medication.<\/p>\n\n\n\n Its significance may be philosophical as much as pharmacological.<\/p>\n\n\n\n It forces us to reconsider the endpoint.<\/p>\n\n\n\n Perhaps successful obesity treatment should not simply ask:<\/p>\n\n\n\n How much weight did we remove?<\/strong><\/p>\n\n\n\n Perhaps it should ask:<\/p>\n\n\n\n How much harmful fat did we remove while protecting muscle, strength, metabolic health and physical independence?<\/strong><\/p>\n\n\n\n That is a much better definition of success.<\/p>\n\n\n\n And if bimagrumab continues to perform well in larger trials, the next generation of obesity treatments may not simply make people smaller.<\/p>\n\n\n\n They may help them emerge from weight loss leaner, stronger and metabolically healthier<\/strong>.<\/p>\n\n\n\n That would be a far more interesting achievement.<\/p>\n\n\n\n ActRIIA and ActRIIB:<\/strong> Activin type II receptors involved in signaling from myostatin, activins and related proteins.<\/p>\n\n\n\n Activin:<\/strong> A member of the transforming growth factor beta family involved in numerous biological processes, including muscle, reproductive and metabolic signaling.<\/p>\n\n\n\n Bimagrumab:<\/strong> An investigational monoclonal antibody that blocks activin type II receptors.<\/p>\n\n\n\n DXA:<\/strong> Dual energy X ray absorptiometry, a technique used to estimate bone density, fat mass and lean mass.<\/p>\n\n\n\n GLP 1:<\/strong> Glucagon like peptide 1, a hormone involved in appetite, glucose regulation and digestion.<\/p>\n\n\n\n Lean mass:<\/strong> Body tissue that is not classified as fat or bone mineral. It includes skeletal muscle but is not identical to skeletal muscle mass.<\/p>\n\n\n\n Myostatin:<\/strong> A signaling protein encoded by the MSTN gene that acts as a negative regulator of skeletal muscle growth.<\/p>\n\n\n\n Sarcopenia:<\/strong> Age associated loss of muscle mass, strength and physical performance.<\/p>\n\n\n\n SMAD2\/3:<\/strong> Intracellular proteins involved in transmitting activin and myostatin signals to the cell nucleus.<\/p>\n\n\n\n Visceral adipose tissue:<\/strong> Fat located deep inside the abdominal cavity around internal organs, strongly associated with cardiometabolic risk when excessive.<\/p>\n\n\n\n Heymsfield, S. B., Aronne, L. J., Montgomery, P., Klickstein, L. J., Coleman, L. A., Dole, K., Mindeholm, L., Spruill, S., Li, X., & Attie, K. M. (2026). Bimagrumab plus semaglutide alone or in combination for the treatment of obesity: A randomized phase 2 trial. Nature Medicine, 32<\/em>, 869\u2013882. https:\/\/doi.org\/10.1038\/s41591-026-04204-0<\/a> (Nature<\/a>)<\/p>\n\n\n\n Heymsfield, S. B., Coleman, L. A., Miller, R., Rooks, D. S., Laurent, D., Petricoul, O., Praestgaard, J., Swan, T., Wade, T., Perry, R. G., Goodpaster, B. H., & Roubenoff, R. (2021). Effect of bimagrumab vs placebo on body fat mass among adults with type 2 diabetes and obesity: A phase 2 randomized clinical trial. JAMA Network Open, 4<\/em>(1), e2033457. https:\/\/doi.org\/10.1001\/jamanetworkopen.2020.33457<\/a> (PubMed<\/a>)<\/p>\n\n\n\n Lach-Trifilieff, E., Minetti, G. C., Sheppard, K., Ibebunjo, C., Feige, J. N., Hartmann, S., Brachat, S., Rivet, H., Koelbing, C., Morvan, F., Hatakeyama, S., Glass, D. J., & Lach-Trifilieff, E. (2014). An antibody blocking activin type II receptors induces strong skeletal muscle hypertrophy and protects from atrophy. Molecular and Cellular Biology, 34<\/em>(4), 606\u2013618. (PubMed<\/a>)<\/p>\n\n\n\n Polkey, M. I., Praestgaard, J., Berwick, A., Franssen, F. M. E., Singh, D., Steiner, M. C., Casaburi, R., Tillmann, H. C., Lach-Trifilieff, E., Roubenoff, R., & Rooks, D. S. (2019). Activin type II receptor blockade for treatment of muscle depletion in chronic obstructive pulmonary disease: A randomized trial. American Journal of Respiratory and Critical Care Medicine, 199<\/em>(3), 313\u2013320. https:\/\/doi.org\/10.1164\/rccm.201802-0286OC<\/a> (PubMed<\/a>)<\/p>\n\n\n\n Medical disclaimer: Bimagrumab remains investigational. This article is for educational purposes and is not medical advice or a recommendation to obtain or use unapproved medications.<\/em><\/p>\n\n\n\n For the past several years, the weight loss conversation has been dominated by GLP 1 drugs such as semaglutide and newer incretin therapies such as tirzepatide.<\/p>\n\n\n\n The results can be extraordinary. But there has always been an uncomfortable footnote hiding beneath those impressive before and after photographs. When someone loses 30, 40, or 50 pounds, how much of that weight was fat, and how much was lean tissue?<\/strong><\/p>\n\n\n\n That question becomes increasingly important as we get older because skeletal muscle is not cosmetic luggage we can casually leave behind. Muscle contributes to strength, glucose disposal, metabolic health, mobility, bone loading, fall prevention, and our ability to remain independent.<\/p>\n\n\n\n Enter bimagrumab<\/strong>, an experimental monoclonal antibody that appears to approach obesity from an entirely different direction.<\/p>\n\n\n\n Instead of primarily making you eat less, bimagrumab interferes with biological signals that restrict muscle growth.<\/p>\n\n\n\n And some of the newest human research suggests something rather remarkable.<\/p>\n\n\n\n It may allow people to lose substantial amounts of fat while preserving, or even increasing, lean mass.<\/strong><\/p>\n\n\n\n That could change what successful weight loss means.<\/p>\n\n\n\n (Heymsfield et al., 2021; Heymsfield et al., 2026). (PubMed<\/a>)<\/p>\n\n\n\n Bimagrumab is a fully human monoclonal antibody originally developed to influence skeletal muscle biology.<\/p>\n\n\n\n Its targets are the activin type II receptors<\/strong>, specifically ActRIIA and ActRIIB.<\/p>\n\n\n\n These receptors sit on cell membranes and participate in signaling from several members of the transforming growth factor beta family, including myostatin and activins<\/strong>.<\/p>\n\n\n\n Myostatin is particularly interesting.<\/p>\n\n\n\n Its biological job includes limiting skeletal muscle growth. You can think of the myostatin system as one of the body\u2019s built in governors preventing unlimited muscle hypertrophy.<\/p>\n\n\n\n Myostatin and related ligands bind activin receptors and stimulate downstream SMAD2\/3 signaling. These signals suppress aspects of muscle differentiation and growth. Bimagrumab interferes with that process.<\/p>\n\n\n\n By blocking both ActRIIA and ActRIIB, it prevents several muscle growth suppressing ligands from activating their receptors.<\/p>\n\n\n\n That distinction matters because bimagrumab is not merely a myostatin inhibitor<\/strong>. It interferes with a broader signaling network involving myostatin, activins, and related ligands (Lach-Trifilieff et al., 2014). (PubMed<\/a>)<\/p>\n\n\n\n The simplified pathway looks like this:<\/p>\n\n\n\n Myostatin \/ activin \u2192 ActRIIA \/ ActRIIB \u2192 SMAD2\/3 signaling \u2192 restriction of muscle growth<\/strong><\/p>\n\n\n\n Bimagrumab blocks ActRIIA and ActRIIB.<\/p>\n\n\n\n The result is reduced inhibitory signaling.<\/p>\n\n\n\n The muscle growth brake loosens.<\/p>\n\n\n\n But something unexpected happened during clinical development.<\/p>\n\n\n\n Researchers began noticing that bimagrumab was not simply affecting muscle.<\/p>\n\n\n\n People were losing substantial amounts of fat.<\/strong><\/p>\n\n\n\n One of the most important early clues came from a randomized Phase 2 clinical trial published in JAMA Network Open<\/em>.<\/p>\n\n\n\n Researchers studied 75 adults with type 2 diabetes and overweight or obesity.<\/p>\n\n\n\n After 48 weeks, participants receiving bimagrumab experienced approximately:<\/p>\n\n\n\n Participants receiving bimagrumab lost roughly 7.5 kilograms of fat while gaining approximately 1.7 kilograms of lean tissue<\/strong> (Heymsfield et al., 2021). (PubMed<\/a>)<\/p>\n\n\n\n Stop for a moment and consider what those numbers mean.<\/p>\n\n\n\n Scale weight fell by around 6.5%.<\/p>\n\n\n\n But fat mass fell by more than 20%.<\/p>\n\n\n\n If you looked only at body weight, you would dramatically underestimate the change occurring inside the body.<\/p>\n\n\n\n And this points toward one of the biggest problems with our obsession with scale weight.<\/p>\n\n\n\n Two people can each lose 20 pounds while experiencing completely different physiological transformations.<\/p>\n\n\n\n One could lose mostly adipose tissue while maintaining muscle.<\/p>\n\n\n\n The other could lose considerable muscle along with fat.<\/p>\n\n\n\n The bathroom scale congratulates both of them equally.<\/p>\n\n\n\n Their physiology and older self may widely disagree!<\/p>\n\n\n\n In March 2026, Nature Medicine<\/em><\/a> published the Phase 2 BELIEVE trial.<\/p>\n\n\n\n This study included 507 adults with obesity<\/strong> and compared bimagrumab, semaglutide, various combinations of the two, and placebo.<\/p>\n\n\n\n Bimagrumab was administered intravenously every 12 weeks, while semaglutide was administered weekly.<\/p>\n\n\n\n At 48 weeks, body weight decreased by approximately 9.3 kilograms with high dose bimagrumab, 14.2 kilograms with semaglutide 2.4 mg, and 17.8 kilograms with the high dose combination (Heymsfield et al., 2026). (Nature<\/a>)<\/p>\n\n\n\n If we stopped there, semaglutide would appear to be the obvious winner.<\/p>\n\n\n\n But then researchers looked inside the weight loss.<\/p>\n\n\n\n That is where the story gets much more interesting.<\/p>\n\n\n\n At 72 weeks, the efficacy analysis found that high dose bimagrumab reduced body weight approximately 10.8%<\/strong>, compared with 15.7%<\/strong> for semaglutide and 22.1%<\/strong> for their high dose combination.<\/p>\n\n\n\n Yet fat mass told another story.<\/p>\n\n\n\n Bimagrumab reduced total fat mass 28.5%<\/strong>.<\/p>\n\n\n\n Semaglutide reduced fat mass 27.8%<\/strong>.<\/p>\n\n\n\n The combination reduced fat mass an extraordinary 45.7%<\/strong>.<\/p>\n\n\n\n And then we arrive at lean mass.<\/p>\n\n\n\n Bimagrumab alone produced an approximately 2.5% increase in lean mass<\/strong>.<\/p>\n\n\n\n Semaglutide produced about a 7.4% decrease<\/strong>.<\/p>\n\n\n\n The combination limited lean mass decline to approximately 2.9%<\/strong>, despite producing considerably greater overall weight loss (Heymsfield et al., 2026).<\/p>\n\n\n\n This may ultimately be bimagrumab\u2019s most important contribution.<\/p>\n\n\n\n For decades, weight management has largely revolved around three familiar measurements:<\/p>\n\n\n\n They are useful, but incomplete. The BELIEVE researchers pointed out that during caloric restriction, incretin therapy and bariatric surgery, approximately 25% to 40% of weight lost can consist of lean mass<\/strong> (Heymsfield et al., 2026). (Nature<\/a>)<\/p>\n\n\n\n Some lean tissue reduction is expected during substantial weight loss.<\/p>\n\n\n\n But particularly in older adults, repeatedly losing large amounts of skeletal muscle could carry consequences.<\/p>\n\n\n\n Less muscle can mean reduced strength reserves, lower glucose disposal capacity, poorer physical function and potentially greater vulnerability to sarcopenia later in life.<\/p>\n\n\n\n This does not mean GLP 1 medications inevitably cause pathological muscle wasting. That claim is far too simplistic.<\/p>\n\n\n\n It means body composition deserves to be monitored<\/strong>, particularly during aggressive weight loss.<\/p>\n\n\n\n And it explains why combining an incretin with a drug that protects lean tissue is such an intriguing idea.<\/p>\n\n\n\n The BELIEVE study produced another finding that deserves more attention.<\/p>\n\n\n\n At 72 weeks, estimated visceral adipose tissue decreased approximately:<\/p>\n\n\n\nThe important points\u00a0first<\/h3>\n\n\n\n
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What Exactly Is Bimagrumab?<\/h3>\n\n\n\n
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The 2021 Study That Changed the Conversation<\/h3>\n\n\n\n
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Then Came the BELIEVE\u00a0Trial<\/h3>\n\n\n\n
Fat Loss Versus Lean Tissue\u00a0Loss<\/h3>\n\n\n\n
The Scale May Be Measuring the Wrong\u00a0Thing<\/h3>\n\n\n\n
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Visceral Fat Might Be the Bigger\u00a0Story<\/h3>\n\n\n\n
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But There Is an Important Catch: Bigger Muscle Is Not Always Better\u00a0Muscle<\/h3>\n\n\n\n
Resistance Training Would Still\u00a0Matter<\/h3>\n\n\n\n
What About Creatine, Peptides and Hormones?<\/h3>\n\n\n\n
And What About\u00a0DNA?<\/h3>\n\n\n\n
Safety Cannot Be an Afterthought<\/h3>\n\n\n\n
The Next Experiment Could Be Even More Interesting<\/h3>\n\n\n\n
![\"\"](\"https:\/\/cdn-images-1.medium.com\/max\/1320\/1*dKxXBFYk2xaha-pUlvi_MQ.png\")
A Better Model of Weight\u00a0Loss<\/h3>\n\n\n\n
Glossary<\/h3>\n\n\n\n
\n\n\n\nReferences<\/h3>\n\n\n\n
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The newest obesity research is forcing us to ask a better question, not simply \u201cHow much weight did you lose?\u201d but \u201cWhat tissue did you\u00a0lose?\u201d<\/h3>\n\n\n\n
The important points\u00a0first<\/h3>\n\n\n\n
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What Exactly Is Bimagrumab?<\/h3>\n\n\n\n
The 2021 Study That Changed the Conversation<\/h3>\n\n\n\n
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Then Came the BELIEVE\u00a0Trial<\/h3>\n\n\n\n
Fat Loss Versus Lean Tissue\u00a0Loss<\/h3>\n\n\n\n
The Scale May Be Measuring the Wrong\u00a0Thing<\/h3>\n\n\n\n
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Visceral Fat Might Be the Bigger\u00a0Story<\/h3>\n\n\n\n
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