A couple months ago I saw this exchange between Kevin D. Hall, Ph.D., who according to Google is a “…tenured Senior Investigator at the National Institute of Diabetes & Digestive & Kidney Diseases (NIDDK),” who discounts the possibility of obese people having abnormally slow metabolisms to account for their obesity and inability to lose weight:
Thanks, this was done 30 years ago: https://t.co/Lc6EDsf8Ia
— Kevin Hall (@KevinH_PhD) July 12, 2022
Dr. Hall cites the study “Discrepancy between Self-Reported and Actual Caloric Intake and Exercise in Obese Subjects,” 1992, as counterevidence against slow metabolisms, instead blaming the under-reporting of calories by unsuccessful dieters.
A Google search shows thousands of results and mentions, with the study as of 2025 having garnered 1773 citations since its publication in 1992, making it one of the most famous studies in human physiology and nutritional science ever:
From the study:
Some obese subjects repeatedly fail to lose weight even though they report restricting their caloric intake to less than 1200 kcal per day. We studied two explanations for this apparent resistance to diet — low total energy expenditure and underreporting of caloric intake — in 224 consecutive obese subjects presenting for treatment. Group 1 consisted of nine women and one man with a history of diet resistance in whom we evaluated total energy expenditure and its main thermogenic components and actual energy intake for 14 days by indirect calorimetry and analysis of body composition. Group 2, subgroups of which served as controls in the various evaluations, consisted of 67 women and 13 men with no history of diet resistance.
To this day it’s still frequently mentioned on social media and the mainstream media.
But the fact that someone who is authoritative posts a link to a study is insufficient reason to trust him. Unlike 99.9% of people online, I actually do read the studies and have the requisite knowledge to at least understand them on a baseline level.
It’s not good–or as they say–trash:
–The study was over 30 years ago, and despite having been cited 1773 times, AFIK/to the best of my knowledge, has NEVER been replicated. Not once.
–The study has ONLY 10 , yes, 10 subjects. Precisely, nine women and one man.
–The results of study does not claim or mean what people think it means. If anything, it shows the opposite, as I will explain.
So in other words, people’s opinions about obesity are still being informed by a study from almost 35 years ago with 10 subjects that has never been replicated.
Dr. Hall not stupid or being disingenuous. He was trying to help, but this is demonstrative of a common problem with science reporting, which is that results are liable to being misinterpreted or misconstrued by the media, the public, and even the scientists themselves. People just uncritically accept this study as truth because it has been cited so many times.
Surely, it must be that simple! Obese people habitually under-report calories; ergo, which why they fail their diets. It’s not metabolism to blame–but rather underreporting intake. Case closed? Or maybe it’s possible for both these things to be true: That a lot of obese or formerly obese people have impaired metabolisms and are under-reporting food.
The thing is, contrary to Dr. Hall and others who sing the praises of this study as settling the matter, the study does not actually exonerate the role of metabolism. This is because the control group are other obese people. Yes, this is a huge detail that is overlooked. The study instead shows that this tiny subset of obese dieters were consuming more calories compared to more successful dieters, but this does not disprove that the control group doesn’t have a slow metabolism, as the control group are also obese people.
From the study:
The energy intake reported by the subjects in group 1 during the 14-day study period was 1028±148 kcal per day, whereas their actual energy intake was 2081±522 kcal per day. Thus, these subjects significantly (P<0.05) underreported their energy intake by a group mean of 1053 kcal per day, or a mean for individual subjects of 47±16 percent (Fig. 2). These subjects underreported their energy intake even more if their total energy expenditure (2468 kcal per day) represents the long-term energy intake required to maintain a stable weight.
Group 1 (the 10 subjects) who failed to lose weight were still not eating that many calories, only 1,800-2200/kcal/day compared to the control group, who were consuming 1,700 kcal/day. 2,000 kcal/day, which is considered the “recommended” guidelines, to still be obese and not lose weight seems pretty bad and could be suggestive of metabolic dysfunction. We’re not talking 10,000 kcal/day like on those food YouTube videos, but modest amounts of food. Moreover, these are not elderly subjects or bedridden/mobility-impaired subjects.
In fairness to the study, they showed that the subjects in group 1 did not have metabolisms that fell more than 10% below predicted regression values, but this is not the same as using non-obese subjects as the control group. It’s possible that people who have no history of obesity may still have faster metabolisms than predicted by regression estimates and or compared to obese people or formerly obese people, controlling for body composition and other factors. The study never set to test that out, so people who make make this inference are reaching for a conclusion that cannot be drawn with the data collected.
The fact that to lose weight requires having to eat as few as 1,200 kcal/day as per the study, if anything, shows how absurdly small amount of food is required for obese people to lose weight. This suggests slow metabolisms can be to blame, among other factors, in agreement with other studies that Dr. Hall evidently failed to cite. The under-reporting of intake is orthogonal to this.