Calorie Deficit but Slow Weight Loss? I Simulated 12 Weeks

"Cut 500 calories a day and lose half a kilo a week." I ran 12 weeks of that through a published model of human metabolism (Hall et al., The Lancet, 2011, the model behind the NIH Body Weight Planner) for one example person, day by day. The result: 4.4 kg, not the 5.4 kg the old rule predicts. Week one is mostly glycogen and water, weeks two and three slow down without being a plateau, and the real deficit shrinks as you lose. Then: what happens at one year, and why adherence matters more than any of the maths. ⚖️ Weighing food is the easiest way to make a calorie deficit real. Digital kitchen food scales on Amazon AU (affiliate link): https://www.amazon.com.au/s?k=digital+kitc... Affiliate disclosure: as an Amazon Associate, Cut Science earns from qualifying purchases at no extra cost to you. It doesn't change what the studies say. The simulation is a simplified Python rebuild of the published equations, not the official NIH tool. It's one example person, not a prediction for you. ⚠️ General information only, not medical or nutrition advice. Talk to your GP or an Accredited Practising Dietitian before making big changes, especially if you have a health condition, are pregnant, or have a history of disordered eating. CHAPTERS 0:00 Intro 1:00 The person and the model 2:13 The 3,500 calorie rule 2:58 Week 1: the whoosh 3:47 Is week 3 a plateau? 4:52 Why the deficit shrinks 5:49 Adaptive thermogenesis 6:45 Bigger deficit, faster loss? 7:16 Past 12 weeks: the plateau 8:21 The factor that matters most 9:28 What to actually expect 10:11 Next in The Deficit Series SOURCES • Hall KD et al. (2011). Quantification of the effect of energy imbalance on bodyweight. The Lancet 378:826-837. https://pmc.ncbi.nlm.nih.gov/articles/PMC3... and web appendix (model equations): https://www.niddk.nih.gov/-/media/Files/BW... • NIH NIDDK Body Weight Planner: https://www.niddk.nih.gov/bwp • Thomas DM et al. (2013). Can a weight loss of one pound a week be achieved with a 3500-kcal deficit? Int J Obes. Observed 20.1 lb vs 27.6 lb predicted by the 3,500 kcal rule. https://pmc.ncbi.nlm.nih.gov/articles/PMC4... • Wishnofsky M (1958). Caloric equivalents of gained or lost weight. Am J Clin Nutr 6(5):542-546. https://doi.org/10.1093/ajcn/6.5.542 • CALERIE 2: Ravussin E et al. (2015), J Gerontol A, https://pmc.ncbi.nlm.nih.gov/articles/PMC4... ; Das SK et al. (2017), Am J Clin Nutr, https://pmc.ncbi.nlm.nih.gov/articles/PMC5... • Fothergill E et al. (2016). Persistent metabolic adaptation 6 years after "The Biggest Loser" competition. Obesity 24:1612-1619. https://pmc.ncbi.nlm.nih.gov/articles/PMC4... ; critique: "Overstated metabolic adaptation after 'The Biggest Loser' intervention", Obesity (2016), https://doi.org/10.1002/oby.21638 SIMULATION ASSUMPTIONS • Example person: male, 35, 178 cm, 95 kg, sedentary (PAL 1.5); initial body fat from Jackson et al. equations; resting rate from Mifflin-St Jeor. • 500 kcal/day (about 2,100 kJ) below starting maintenance, held constant; 50% carbohydrate diet. • Model: energy densities of fat and lean tissue, Forbes partitioning, glycogen with bound water, thermic effect of food and adaptive thermogenesis as in Hall et al. (2011). Simplified: no separate extracellular-fluid sodium response to diet changes beyond the model's basic term. • The adherence scenario (78% of the planned deficit for 6 months, then 38%) is illustrative, loosely shaped on CALERIE 2's reported drift, not a fit to that trial. Narration uses a synthetic (text-to-speech) voice. All charts and music are original. #caloriedeficit #weightloss #nutritionscience