Uploaded July 2026 | Updated September 2026, 3 weeks ago
Is weight loss really just Calories in, Calories out? The equation is true, but "just count your Calories" is bad advice for most people, and almost every objection to it is pointing at something real. In part two of our energy balance series, Dr. Jordan Feigenbaum takes the biggest "it's not Calories, it's ___" claims (metabolism, thyroid, cortisol, PCOS, insulin, the type of food) and tests each against the best evidence. The verdict: none of them breaks the equation. Every one is a hand on a lever that moves Calories in or Calories out, not a hole in the math.
In this episode: why your metabolism does not crash at 40, how small real metabolic adaptation actually is after weight loss, why hypothyroid weight is mostly water, what the cortisol and PCOS (now PMOS) data show, how absorption and cooking move Calories only at the edges, why even dietitians miscount their own intake, and why the carbohydrate-insulin model fails three tests, including the GLP-1 drugs that raise insulin and still produce the biggest weight loss we have ever approved.
Part two of three: willpower, Calories in Calories out, then GLP-1 drugs. Next week: are GLP-1s cheating?
Chapters
0:00 Is it really just calories in, calories out?
0:18 The willpower episode and the through-line
2:10 Thermodynamics: what sets both sides
2:41 Your metabolism is three things
4:05 Claim 1: my metabolism crashed
4:24 No cliff at 40: the doubly labeled water study
5:33 Real metabolic adaptation after weight loss
6:56 Why your food diary lies
7:49 Claim 2: it's my hormones
8:07 Thyroid: mostly water
9:36 Cortisol: explains about 1 percent
11:12 PCOS is now PMOS
13:06 Menopause
14:18 Claim 3: a calorie isn't a calorie
16:48 Absorption: nuts, cooking, eggs
19:44 Why calorie counting fails
21:12 Claim 4: it's not Calories, it's insulin
22:02 Testing the carbohydrate-insulin model
25:52 The GLP-1 drugs that should end it
28:34 The whole list, claim by claim
29:53 What to actually do
30:42 Next week: are GLP-1s cheating?
Resources:
Barbell Medicine coaching and templates: barbellmedicine.com
barbellmedicine.com/shop/subscriptions/plus-podcast-subscription
barbellmedicine.com/shop/subscriptions/barbell-medicine-premium
Signal book pre-order: barbellmedicine.com/shop/learning/signal
Pontzer et al., Science 2021. doi.org/10.1126/science.abe5017
Muller et al., Am J Clin Nutr 2015. doi.org/10.3945/ajcn.115.109173
Lichtman et al., N Engl J Med 1992. doi.org/10.1056/NEJM199212313272701
Karmisholt et al., J Clin Endocrinol Metab 2011. doi.org/10.1210/jc.2010-1521
Lee et al., Endocr Pract 2014. doi.org/10.4158/EP14072.OR
van der Valk et al., Obes Rev 2022. doi.org/10.1111/obr.13376
Nikokavoura et al., Diabetes Metab Syndr Obes 2015. doi.org/10.2147/DMSO.S85134
Greendale et al., JCI Insight 2019. doi.org/10.1172/jci.insight.124865
Lejeune et al., Am J Clin Nutr 2006. doi.org/10.1093/ajcn/83.1.89
Bray et al., JAMA 2012. doi.org/10.1001/jama.2011.1918
Novotny et al., Am J Clin Nutr 2012. doi.org/10.3945/ajcn.112.035782
Baer et al., J Nutr 2016. doi.org/10.3945/jn.115.217372
Baer et al., Br J Nutr 2012. doi.org/10.1017/S0007114511002649
Evenepoel et al., J Nutr 1998. doi.org/10.1093/jn/128.10.1716
Hall et al., Cell Metabolism 2019. doi.org/10.1016/j.cmet.2019.05.008
Champagne et al., J Am Diet Assoc 2002. doi.org/10.1016/S0002-8223(02)90316-0
Hall et al., Cell Metabolism 2015. doi.org/10.1016/j.cmet.2015.07.021
Wilding et al., N Engl J Med 2021. doi.org/10.1056/NEJMoa2032183
Jastreboff et al., N Engl J Med 2022. doi.org/10.1056/NEJMoa2206038
Is weight loss really just Calories in, Calories out? The equation is true, but "just count your Calories" is bad advice for most people, and almost every objection to it is pointing at something real. In part two of our energy balance series, Dr. Jordan Feigenbaum takes the biggest "it's not Calories, it's ___" claims (metabolism, thyroid, cortisol, PCOS, insulin, the type of food) and tests each against the best evidence. The verdict: none of them breaks the equation. Every one is a hand on a lever that moves Calories in or Calories out, not a hole in the math.
In this episode: why your metabolism does not crash at 40, how small real metabolic adaptation actually is after weight loss, why hypothyroid weight is mostly water, what the cortisol and PCOS (now PMOS) data show, how absorption and cooking move Calories only at the edges, why even dietitians miscount their own intake, and why the carbohydrate-insulin model fails three tests, including the GLP-1 drugs that raise insulin and still produce the biggest weight loss we have ever approved.
Part two of three: willpower, Calories in Calories out, then GLP-1 drugs. Next week: are GLP-1s cheating?
Chapters
0:00 Is it really just calories in, calories out?
0:18 The willpower episode and the through-line
2:10 Thermodynamics: what sets both sides
2:41 Your metabolism is three things
4:05 Claim 1: my metabolism crashed
4:24 No cliff at 40: the doubly labeled water study
5:33 Real metabolic adaptation after weight loss
6:56 Why your food diary lies
7:49 Claim 2: it's my hormones
8:07 Thyroid: mostly water
9:36 Cortisol: explains about 1 percent
11:12 PCOS is now PMOS
13:06 Menopause
14:18 Claim 3: a calorie isn't a calorie
16:48 Absorption: nuts, cooking, eggs
19:44 Why calorie counting fails
21:12 Claim 4: it's not Calories, it's insulin
22:02 Testing the carbohydrate-insulin model
25:52 The GLP-1 drugs that should end it
28:34 The whole list, claim by claim
29:53 What to actually do
30:42 Next week: are GLP-1s cheating?
Resources:
Barbell Medicine coaching and templates: barbellmedicine.com
barbellmedicine.com/shop/subscriptions/plus-podcast-subscription
barbellmedicine.com/shop/subscriptions/barbell-medicine-premium
Signal book pre-order: barbellmedicine.com/shop/learning/signal
Pontzer et al., Science 2021. doi.org/10.1126/science.abe5017
Muller et al., Am J Clin Nutr 2015. doi.org/10.3945/ajcn.115.109173
Lichtman et al., N Engl J Med 1992. doi.org/10.1056/NEJM199212313272701
Karmisholt et al., J Clin Endocrinol Metab 2011. doi.org/10.1210/jc.2010-1521
Lee et al., Endocr Pract 2014. doi.org/10.4158/EP14072.OR
van der Valk et al., Obes Rev 2022. doi.org/10.1111/obr.13376
Nikokavoura et al., Diabetes Metab Syndr Obes 2015. doi.org/10.2147/DMSO.S85134
Greendale et al., JCI Insight 2019. doi.org/10.1172/jci.insight.124865
Lejeune et al., Am J Clin Nutr 2006. doi.org/10.1093/ajcn/83.1.89
Bray et al., JAMA 2012. doi.org/10.1001/jama.2011.1918
Novotny et al., Am J Clin Nutr 2012. doi.org/10.3945/ajcn.112.035782
Baer et al., J Nutr 2016. doi.org/10.3945/jn.115.217372
Baer et al., Br J Nutr 2012. doi.org/10.1017/S0007114511002649
Evenepoel et al., J Nutr 1998. doi.org/10.1093/jn/128.10.1716
Hall et al., Cell Metabolism 2019. doi.org/10.1016/j.cmet.2019.05.008
Champagne et al., J Am Diet Assoc 2002. doi.org/10.1016/S0002-8223(02)90316-0
Hall et al., Cell Metabolism 2015. doi.org/10.1016/j.cmet.2015.07.021
Wilding et al., N Engl J Med 2021. doi.org/10.1056/NEJMoa2032183
Jastreboff et al., N Engl J Med 2022. doi.org/10.1056/NEJMoa2206038
