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This will be a relatively short post, but due to my recent offering, I re-read some of the original Shai et.al LF v. Mediterranean v. LC diet comparison study and had some commentary to add. First, leaving aside reasons for withdrawal, there was a significant difference in compliance/completion between the three groups -- roughly 90% of LF, 85% of MDTN and 78% of LC subjects that completed the 2-year intervention.
The analysis in Shai was "intent to treat" -- I so wish the raw data were available for such studies so that truly valuable information on what a truly compliant-successful-completer might hope to attain following a diet plan. Isn't that what it is supposed to be all about?? But it is what it is, and in the results reported in the mass media, the ITT data was counted. This generally means that all subjects data are included at all timepoints. When they drop out, their last data points are commonly continued forward. This is especially interesting, to me, for the LC group (but also MDTN). You see 4 of the 109 randomized to LC dropped out before the diet, this means their initial data were carried throughout and at early time points the low carbers lost even more weight at six months than the average might imply! But then it gets interesting, because 3 more withdrew at the 6 month mark, and 13 more at the 1 year mark. This means that 3 early losses were likely carried through the calcs at all subsequent time points, and 13 subjects had 1 year data carried forward to the 2 year mark. Still, they did give data for the completers which is favorable to the LC group as a whole.
All 322 participants at 2 years:
LF: 2.9±4.2 kg MDTN: 4.4±6.0 kg LC: 4.7±6.5 kg
Among 272 participants who completed 2 years:
LF: 3.3±4.1 kg MDTN: 4.6±6.0 kg LC: 5.5±7.0 kg
So... stick with it to some degree and LC seems to work nominally better. Of course these are just self-reported adherents and there is little-to-no data available as to the degree of compliance. Still, you have roughly 12% more of the initial group of low-fatters represented at two years than low-carbers, and I think this bears mentioning in terms of dedication to the plan.
But here's some other data we don't hear about. This study was in mostly (86%) men, the entire cohort being middle-aged (avg. age 54).
Among all 277 males at 2 years: (values in parentheses are 95% CI)
LF: 3.4 kg (2.5-4.3) MDTN: 4.0 kg (3.0-5.1) LC: 4.9 kg (3.6-6.2)
Among all 45 females at 2 years
LF: 0.1 kg (1.9-2.2) MDTN: 6.2 kg (1.9-10.2) LC: 2.4 kg (2.2-6.9)
This is interesting folks!!! Look at that. Granted we're not talking about a lot of women, but the men did nominally better on LC vs the other approaches. But the low carbing women did more poorly on both LF & LC diets, and more poorly on LC after two years than the men did on LF!! Not that they did great on LF, essentially breaking even with little variability, but look at the MDTN! With great variation (why they report normal std. deviation or std. error for raw data in the primary analysis and %CI (estimated variation, not raw data error/variation) for this data I'll never understand. But it doesn't matter. The weight loss superstars in all of this, if there are any to be lauded, were the women on the Mediterranean diet!!
And so, four years later, we're not given this breakdown. Sigh. But I think we can make a few inferences that are far more valid than guruspeak interpretations of same. The MDTN group regained less on average. Did the women who "ruled" at the 2 year mark carry the diet? Perhaps.