Obesity treatment is shifting fast. For years the standard toolkit was lifestyle counseling plus a handful of older medications. New drug classes now target the actual biology of the disease: hormonal signaling, metabolic rate, body composition. Three groups matter most right now. Nutrient-stimulated hormone-based therapies. Oral small molecule receptor agonists. And activin receptor pathway inhibitors.
NuSHs mimic or amplify the body’s own hormonal response to food. GLP-1 increases satiety, slows gastric emptying, and supports insulin secretion (Wilding et al., N Engl J Med, 2021). GIP regulates fat metabolism and glucose response (Frías et al., N Engl J Med, 2021). Amylin, co-secreted with insulin, works as its own satiety signal (Dehestani et al., J Obes Metab Syndr, 2021). PYY reduces appetite and energy intake (Schmidt et al., Am J Physiol Endocrinol Metab, 2014). Oxyntomodulin reduces intake too, and also raises energy expenditure (Wynne et al., Int J Obes, 2006).
Several drugs in this class are already in trials, and CagriSema pairs an amylin analogue with a GLP-1 receptor agonist, reducing body weight by 17.1 percent in 20 weeks in a Phase 1b trial, not Phase 3 (Enebo et al., Lancet, 2021). Survodutide, a GLP-1 and glucagon receptor agonist, produced weight loss of up to 18.7 percent over 46 weeks (Le Roux et al., Lancet Diabetes Endocrinol, 2024). Retatrutide, which hits GIP, GLP-1, and glucagon receptors together, produced a 24.2 percent reduction over 48 weeks in Phase 2 testing. Women lost about 28.5 percent of body weight, men about 21.9 percent (Jastreboff et al., N Engl J Med, 2023). Oral semaglutide at 50 mg reached 17.4 percent weight loss at 68 weeks, with 37 percent of participants losing more than a fifth of their body weight (Knop et al., Lancet, 2023). Mari-tide is still in Phase 2, with promising early results.
Small molecule receptor agonists are the other track, and their edge is simple: a pill instead of a needle. Orforglipron produced about 14.7 percent weight loss at 36 weeks, in range with the injectables (Wharton et al., N Engl J Med, 2023). Danuglipron is behind it. Early Phase 2 data, in patients with type 2 diabetes rather than obesity specifically, showed reduced appetite alongside improved glucose and weight outcomes (Saxena et al., Diabetes Obes Metab, 2023). Whether that holds up in an obesity-only population is still unclear.
Activin receptor pathway inhibitors take a different approach. They target pathways that preserve muscle while fat comes off, since traditional weight loss burns muscle right along with fat. These drugs try to change that ratio (Heymsfield et al., JAMA Netw Open, 2021).
Bimagrumab, a monoclonal antibody that blocks the activin type II receptor, reduced fat mass by 20.5 percent while increasing lean mass by 3.6 percent over 48 weeks in trials. Combine it with a GLP-1 drug like semaglutide or tirzepatide and the body-composition effect gets stronger still. Taldefgrobep, a myostatin inhibitor originally developed for Duchenne muscular dystrophy, is now being tested for obesity. SRK-439 is another myostatin-targeting antibody in development, aimed at fat loss without the lean-mass cost.
What sets these treatments apart is what the weight loss is made of: more muscle retained, metabolic markers that move too, alongside the pounds lost. That’s a real shift, for patients who may get more durable results and fewer complications, and for clinicians who get more tools to match therapy to the person in front of them.
References:
Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384:989-1002. PMID 33567185. https://pubmed.ncbi.nlm.nih.gov/33567185/
Frías JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). N Engl J Med. 2021. PMID 34170647. https://pubmed.ncbi.nlm.nih.gov/34170647/
Dehestani B, Stratford NR, le Roux CW. Amylin as a Future Obesity Treatment. J Obes Metab Syndr. 2021;30(4):320-325. PMID 34929674. https://pubmed.ncbi.nlm.nih.gov/34929674/
Schmidt JB, Gregersen NT, Pedersen SD, et al. Effects of PYY3-36 and GLP-1 on energy intake, energy expenditure, and appetite in overweight men. Am J Physiol Endocrinol Metab. 2014;306(11):E1248-56. PMID 24735885. https://pubmed.ncbi.nlm.nih.gov/24735885/
Wynne K, Park AJ, Small CJ, et al. Oxyntomodulin increases energy expenditure in addition to decreasing energy intake in overweight and obese humans: a randomised controlled trial. Int J Obes (Lond). 2006;30(12):1729-1736. PMID 16619056. https://pubmed.ncbi.nlm.nih.gov/16619056/
Enebo LB, Berthelsen KK, Kankam M, et al. Lancet. 2021;397:1736-1748. Phase 1b trial. PMID 33894838. https://pubmed.ncbi.nlm.nih.gov/33894838/
Le Roux CW, et al. Lancet Diabetes Endocrinol. 2024;12:162-173. PMID 38330987. https://pubmed.ncbi.nlm.nih.gov/38330987/
Jastreboff AM, et al. N Engl J Med. 2023;389:514-526. PMID 37366315. https://pubmed.ncbi.nlm.nih.gov/37366315/
Knop FK, et al. Lancet. 2023 (OASIS 1). PMID 37385278. https://pubmed.ncbi.nlm.nih.gov/37385278/
Wharton S, Blevins T, Connery L, et al. N Engl J Med. 2023;389:877-888. PMID 37351564. https://pubmed.ncbi.nlm.nih.gov/37351564/
Saxena AR, Frias JP, Brown LS, et al. Tolerability, safety and pharmacodynamics of oral, small-molecule GLP-1 receptor agonist danuglipron for type 2 diabetes. Diabetes Obes Metab. 2023. PMID 37311722. https://pubmed.ncbi.nlm.nih.gov/37311722/
Heymsfield SB, Coleman LA, Miller R, et al. Effect of Bimagrumab vs Placebo on Body Fat Mass Among Adults With Type 2 Diabetes and Obesity. JAMA Netw Open. 2021;4(1):e2033457. PMID 33439265. https://pubmed.ncbi.nlm.nih.gov/33439265/
Board Certified in Obesity Medicine and Family Medicine
This blog is for educational purposes only and does not constitute individual medical advice. Always consult your own physician before making changes to your health, medications, or treatment plan.
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