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by user052919
1212 days ago
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The data was based on behavior between 1999-2014, which means it was behavior that almost certainly was not health motivated since intermittent fasting wasn't popular then. So I think you have to ask: why were these people skipping meals? I think there are a lot of possible explanations and they are all potential confounds. Like, one obvious reason people skip meals is that they don't have time. If you don't have time to eat, you're probably working long hours and really stressed out. Stress could easily contribute to CVD or otherwise take years off your life. Another obvious reason to skip meals: you don't have money to buy food. Poverty is well known to lead to worse health outcomes. Or one more: people skip meals because they have no appetite. What's a big cohort that routinely skips meals because they have no appetite? The elderly. Maybe they ruled these kinds of things out in the full paper (I've only read the abstract) but so far I'm unimpressed. |
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> As shown in Table 1, compared with participants with three meals per day, participants eating fewer than three meals per day were more likely to be younger, men, non-Hispanic Black, with less education and lower family income, current smokers, heavy alcohol drinkers, higher physical activity levels, lower total energy intake and lower diet quality, food insecure, and higher frequency of snacks.
They control for these factors in the statistical analysis, to different extents in three different models:
> Model 1 adjusted for age, gender, and race and ethnicity. Model 2 additionally adjusted for education, income, smoking status, alcohol intake, physical activity levels, total energy intake, HEI-2010 score, household adult food insecurity status, and snacks frequency. Model 3 further adjusted for baseline diabetes, hypertension, hypercholesterolemia, CVD, cancer, and BMI status, because these variables may be mediators between meal frequency, intervals and timing, and mortality.
This is an issue. Controlling for the variables in the model helps somewhat, but it's inevitable that the populations are also different in other relevant ways that are not captured in the covariates (e.g. stress levels).
They're also reporting dozens of results (18 in Table 2, another 18 in Table 3, 12 in Table 4) but doing no correction for multiple testing. Given that many of the confidence intervals only barely exclude 1, this is an issue.
Finally, and most damning--the effects almost entirely disappear if they exclude people who had cancer or cardiovascular disease at the beginning of the study. This is hidden in the supplementary material of the paper, not discussed at all within the main body of the paper. Of the effects cited in the abstract the only one that survives excluding people who had cancer or cardiovascular disease at baseline is that people who skip breakfast appear to have higher risk of cardiovascular disease-related mortality.
Given that the study is labelled "prospective" and one of the outcomes studied is death from cardiovascular disease, IMO it is dishonest to not note that the claimed effects disappear if you exclude people who already had cardiovascular disease when the study started.