The FastDay Forum

http://www.ncbi.nlm.nih.gov/pubmed/23591120

http://journals.cambridge.org/action/di ... id=8879118

This is the science behind the "2 day diet" from the Breast Cancer researchers funded by Genesis UK (Manchester).

It's a complex trial, with three diets. The 2 day "intermittent carbohydrate and energy reduction" IECR is the closest to the 5:2 fast diet except that it uses two consecutive days and the carbohydrate content of the diet is limited to 40g on those two days. Protein tends to be fairly high, although the tables showing what was actually eaten are currently missing from the web.

The second Intermittent regime is ICER plus additional ad-lib proteins and unsaturated fat (IECR + PF). So the same carb restriction for two consecutive days but additional food on tap if desired.

The third arm of Daily Energy Restriction (DER) is a 25% restriction in calories every day - the same as IECR should provide by restricting to 600-650 cals for 2 days a week and eating to energy demand (TDEE) the other 5 days.

In practice the intermittent groups also restricted feed day calories....

Both IECR groups were instructed to have a euenergetic diet
during the 5 d periods between the restrictions but, instead,
had a ‘carry-over effect’ of the reduced intake of energy and
carbohydrate on these non-restricted days, which was signifi-
cantly lower than the diet that we prescribed. At 3 months, the
mean energy intake for a ‘non-restricted’ day of the IECR
group was 5716 (95 % CI 5215, 6216) kJ compared with their
prescribed diet of 8314 (95 % CI 8080, 8540) kJ, on average
32 % less than prescribed.

Results are made slightly hard to interpret by the 3 kg differences in mean weight at baseline between the groups, with IECR the lightest group, IECR + PF 3kg heavier on average and DER a further 3 kg heavier. Probably not statistically significant, but makes reading tables difficult.

Anyway, results.....

Changes in weight, adiposity and body circumferences.
The proportions of the three groups achieving 5 % or greater
weight loss at 3 months were 65 % (IECR), 58 % (IECR + PF)
and 40 % (DER) (P=0·076). Both IECR groups
experienced significantly greater and comparable reductions in body fat than the DER group (IECR P=0·007 and IECR + PF
P=0·019), but no significantly greater reductions in weight,
waist, hip and bust circumferences (Table 3). There were
small reductions in FFM in all the three groups. The median
percentage of weight lost, which was FFM, was less in the
IECR + PF group (20·4 (95 % CI 13·2, 27·2) %) compared
with both IECR (36·0 (95 % CI 26·4, 41·3) %, P=0·009) and
DER (29·3 (95 % CI 25, 38·1) %, P=0·048) groups.

"At 3 months, the mean energy intake for a ‘non-restricted’ day of the IECR group was ... on average 32 % less than prescribed."

That's interesting - seems to confirm that fasting naturally 'resets' appetite and attitude to food after a while.

Thanks for this Phil. I would imagine that the lower calorie intake in the fasting groups accounts for the greater weightloss? Do they say in the full paper?

Also of interest is this:

During the weight maintenance phase, 1 d of IECR or IECR+PF per week maintained the reductions in insulin resistance and weight.

Confirms that 6:1 continues to give some benefits at least.

carorees wrote: Thanks for this Phil. I would imagine that the lower calorie intake in the fasting groups accounts for the greater weightloss? Do they say in the full paper?

Some of that is in the Supplementary Tables which are currently missing (I emailed them). I'm hoping there's an analysis of what was actually being eaten.

The apparent comparable loss of body fat between the IECR and IECR+PF groups appears at odds with the higher reported higher energy intake in the IECR+PF group. Part of this may be the slightly higher protein intake with IECR+PF (mean 1·2 (95 % CI 1·1, 1·2) g/kg body weight v. mean 1·0 (95 % CI 0·9, 1·1) g/kg for the IECR group; mean 1·0 (95 % CI 0·9, 1·1) g/kg for the DER group; P= 0·08). Although not significantly greater, higher protein intakes will help maximise the loss of fat and limit the loss of FFM for a given energy restriction( 52 ), and may evoke a small increase in energy expenditure and greater fat oxidation( 53 ). Alternatively, the reported higher energy intake with IECR+PF may not actually be higher, and could reflect biased under-reporting of carbohydrate rather than protein foods( 54 ), and thus inflate reported intakes with the higher-protein IECR+PF diet.

The success of both IECR diets is not only linked to the adherence to the 2 d restriction, but is also attributable to the spontaneous restriction of energy and carbohydrate on non-restricted days. Intakes on these days in the IECR groups were comparable with those of the DER group. This is an important observation and confirms the present data and the data of others which show that intermittent dieting does not lead to disordered eating and overconsumption on non-restricted days( 21 – 23 , 50 , 51 ). This observation would need to be replicated in future studies, but raises the intriguing possibility that IER may be an effective way of achieving short spells of greater restriction as well as a lesser restriction for the remainder of the week.

Important statement:

This is an important observation and confirms the present data and the data of others which show that intermittent dieting does not lead to disordered eating and overconsumption on non-restricted days( 21 – 23 , 50 , 51 ).

Memorize and repeat to all the sceptics!!!

Oh, and note how they use the term 'intermittent dieting' not 'intermittent fasting'? It avoids that scary word...fasting...

Personally I prefer to use the term "fasting" for actual fasting, not for calorie reduction. It's more precise.

As we have lots of words to choose from we may as well use the correct one
Perhaps "modified fasting" ?

Agreed, the confusion over terms is a real problem!

Bump

The study discussed in this thread is the basis of the Daily Mail's two day diet. It has similarities to 5:2 but it's not quite the same. The study authors also have a book.