Is Obesity a Willpower Problem? The Biology of Weight, Diets, and GLP-1s

Obesity roughly tripled in about 50 years, and the genes didn't change in that time. So if body weight isn't a willpower problem, what is it? Dr. Jordan Feigenbaum and Dr. Austin Baraki walk through what actually sets your weight: the adoption and twin studies behind the genetics, the "defended range" your biology fights to hold, the food environment that does most of the eating for you, and where GLP-1 medications actually work. Along the way — why diets regain after you white-knuckle them, what The Biggest Loser six-year data show about resting metabolism, and four willpower myths worth retiring. Hosted by Dr. Jordan Feigenbaum and Dr. Austin Baraki, co-founders of Barbell Medicine. Timestamps 00:00 Cold open: Danny Cahill and The Biggest Loser 01:03 What we mean by "willpower" 05:48 Obesity tripled in ~60 years: the one number 06:31 Adoption and twin studies: genes vs. household 09:37 Set point vs. the defended range 10:37 Gene–environment mismatch 14:03 In the clinic: a lifelong weight history 19:18 Losing weight vs. keeping it off 20:26 Appetite doesn't reset (Sumithran) 25:52 Metabolic adaptation and the Biggest Loser data 34:07 Part 2: eating on autopilot 35:10 Portion size runs the meal 39:12 What changed in the food supply 40:42 Same genes, new environment: Pima and immigrants 43:20 Why ultra-processed food is easy to overeat 50:28 Processing vs. calories: the Hall ward study 52:36 When the brain changes eating: gourmand syndrome 1:00:01 Why the willpower story stuck 1:01:08 Taft, Churchill, and the intelligence myth 1:02:43 Does intelligence predict weight? (sibling study) 1:11:16 Are GLP-1s cheating? What they actually do 1:15:10 Beyond the scale: muscle, health, nutrition 1:24:21 Myth-busting: lightning round 1:39:04 Three takeaways: what to actually do 1:41:00 Danny Cahill, revisited Resources Barbell Medicine coaching and templates: https://www.barbellmedicine.com https://www.barbellmedicine.com/shop/... https://www.barbellmedicine.com/shop/... Signal book pre-order: https://www.barbellmedicine.com/shop/... Coaching, programs & templates: https://www.barbellmedicine.com/ Obesity prevalence 1960–2023. NCHS Health E-Stats 2024. Obesity prevalence 2021–2023. NCHS Data Brief 508, 2024. Hill & Peters. Environmental contributions to obesity. Science 1998. Morton et al. Protein supplementation & resistance training. Br J Sports Med 2018. Stunkard et al. Adoption study of human obesity. NEJM 1986. Stunkard et al. BMI of twins reared apart. NEJM 1990. Speakman et al. Set points, settling points. Dis Model Mech 2011. Kalm & Semba. Ancel Keys & the Minnesota Experiment. J Nutr 2005. Sumithran et al. Hormonal adaptations to weight loss. NEJM 2011. Fothergill et al. Metabolic adaptation after 'Biggest Loser.' Obesity 2016. Hall. 'Biggest Loser' reinterpreted. Obesity 2022. Cohen & Farley. Eating as automatic behavior. Prev Chronic Dis 2008. Rolls et al. Portion size & energy intake. Am J Clin Nutr 2002. Diliberti et al. Portion size in a restaurant meal. Obes Res 2004. Hollands et al. Portion/package/tableware size. Cochrane 2015. Hall et al. Ultra-processed diets & calorie intake (RCT). Cell Metab 2019. Pontzer et al. Hunter-gatherer energetics & obesity. PLoS One 2012. Careau et al. Energy compensation & adiposity. Curr Biol 2021. Miller et al. 25 years of weight loss research. Int J Obes 1997. Gaesser & Angadi. Weight loss vs fitness. iScience 2021. USDA ERS. Loss-Adjusted Food Availability. Steele et al. UPF & added sugars, US diet. BMJ Open 2016. Wang et al. UPF trends, US youth. JAMA 2021. Schulz et al. Type 2 diabetes in Pima Indians. Diabetes Care 2006. Goel et al. Obesity in US immigrants by residence. JAMA 2004. Papavramidou et al. Galen on obesity. World J Surg 2004. Haslam & Haslam. Fat, Gluttony and Sloth. Liverpool UP 2009. Townend. Moralizing of obesity. Crit Soc Policy 2009. Levine. Taft & medical management of obesity. Ann Intern Med 2013. Wright et al. Cognitive ability & BMI. PLoS Med 2023. GLP-1 receptor agonist weight loss mechanisms. Am J Med 2025. Wilding et al. Semaglutide (STEP 1). NEJM 2021. Jastreboff et al. Tirzepatide (SURMOUNT-1). NEJM 2022. Grannell et al. Obesity & responsibility. Obes Rev 2021. Al Khatib et al. Sleep deprivation & energy balance. Eur J Clin Nutr 2017. Helms et al. Natural bodybuilding contest prep. J Int Soc Sports Nutr 2014. Garthe et al. Weight-loss rate & body composition. Int J Sport Nutr Exerc Metab 2011.