Summary:
Continuing on with discussion of: Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial
Previous posts in this series:
Part I: Critique of the Study Design
Part II: $12 Million for 12% Weight Loss?
Part III: Some "Early" Lessons
Part IV: Insulin Resistance Does Not Hamper Weight Loss
This post should perhaps have come first, but it has taken a while to look deeply at the data for the primary outcome -- total energy expenditure measured by doubly labeled water -- and related outcomes of intake and resting energy expenditure.
In this study, all participants were paid to participate, AND provided free food for ~8 months. Said food was professionally and meticulously prepped, weighed, measured, individualized to provide each subject with some pretty exact caloric level and macronutrient composition. The test phase (in other words, the study proper) involved maintaining a consistent weight (to within ±2 kg), for a considerable length of time: 20 weeks, assessed at the midpoint and the end.
In the previous study, a roughly 300 calorie/day increase in TEE was observed during 4 weeks of isocaloric feeding, producing no weight loss. This was essentially dismissed as "not enough time to show weight loss" {paraphrase} .... So in the current study, the average change in TEE masks the often wild swings of up to 2000 calories per day between 10 week maintenance time points. If this increase (or decrease) in expenditure is truly real, the subjects would HAVE to have adjusted intake accordingly over the course of several weeks in order to maintain consistent weight.
In the previous study, a roughly 300 calorie/day increase in TEE was observed during 4 weeks of isocaloric feeding, producing no weight loss. This was essentially dismissed as "not enough time to show weight loss" {paraphrase} .... So in the current study, the average change in TEE masks the often wild swings of up to 2000 calories per day between 10 week maintenance time points. If this increase (or decrease) in expenditure is truly real, the subjects would HAVE to have adjusted intake accordingly over the course of several weeks in order to maintain consistent weight.
This post is about the massive discrepancies between intake and TEE data (also compared with REE), and the inexcusable near-dismissal of these discrepancies in the journal article.
Bottom Line:
Either the DLW-TEE data is (for reasons that can be discussed) unreliable/inaccurate, or the intake data is unreliable. If the TEE data is problematic, how can a result of a difference of means of 250 cal/day be justifiably defended as significant/meaningful, when we see no such difference in intake? If the intake data is problematic, then how can we conclude anything from a "diet comparison", because significant deviations in caloric intake would render the strict macro compositions totally irrelevant.
Either way, the researchers failed to address this glaring problem with the results study. Further, the discrepancies in these two data sets are so egregious that it is impossible that both can be considered accurate and reliable. It has to be one or the other. Based on the data for Resting Energy Expenditure (REE), the needle points to the intake data as the more reliable measure.