We owe an incalculable debt to scientists but they could have done with a crash course in tact before laying their latest, inevitably disempowering, tranche of findings on us: intermittent fasting could kill you, they now tell us in their pitiless way. Also, high-intensity interval training (HIIT) could make you fatter.
These are conclusions from two peer-reviewed trials, their methodology disclosed and above board. They give two rude fingers to other reputable trials over umpteen years that hailed fasting and HIIT as life-saving. Does science ever say sorry? Science launched all that tummy rumbling and circuit exhaustion, with their attendant apps and smuggery. But now it’s all yeah, nah.
Fortunately – though also infuriatingly – closer reading of these new findings shows they’re inconclusive because the studies’ parameters were too limited to establish cause and effect.
Short-term studies have shown regular, time-limited eating can promote heart and metabolic health. But this, the first long-term study of 20,000 regular fasters over a median eight years, has found their risk of serious heart disease was nearly twice that of non-fasters. This was, to put it mildly, not what the study’s Chinese and American researchers expected. They urged people not to read too much into the results because they couldn’t tell whether fasting was the actual cause of the elevated risk and would have to do more trials.
This prompts two responses: to ask why the blithering hell they bothered studying fasters if this couldn’t tell them what effect the fasting itself had, and to repeatedly bang one’s head on the nearest hard surface in exasperation – a probable risk to brain health and another impact those researchers would not have anticipated.
Anyway, here’s the kicker: not only did the study not ascertain what sort of food the fasters were eating, but it didn’t grade for many of their other health-risk factors.
Many were likely to be in poorer-than-average health, and/or with significant co-morbidities – which, to state the obvious, is why many, possibly most, people try fasting in the first place. Many could have been in a cohort with such bad cardio prognoses that their risk factors actually dropped, even though the overall result looked sub-par for an average data pool.
If fasters cram their “eating window” with cake and chips, that, too, will erode any possible benefits.
The HIIT study was a bit more watertight, but – small head bang – the subjects were mice. Mice put through 30 minutes’ intensive exercise gained weight in the 24 hours afterwards, whereas mice given a longer, more moderate workout did not – despite both groups being fed the same amounts.
Japanese researchers noticed the HIIT squeakers subsequently moved around a lot less than the moderately moved mice, and had a slightly lower body temperature. That likely meant the HIIT group used less energy overall. Hormonal responses to the high-cardio burst further slowed their metabolisms. Again, the researchers cautioned, they couldn’t be sure about any of this until further trials. On humans.
To classify this a let-down, given years of previous reputable, peer-reviewed research identifying HIIT as a metabolism elevator for up to 24 hours after exercise, is a bitter understatement. Anyone who’s been plodding on with longish, moderate runs or brisk walks has been made to feel an ignorant numpty.
Who’s the numpty now, eh, science? We’ll see your Japanese trial and up you another reputable, peer-reviewed study from Canada: a control group of moderate, long-duration movers – human – who burnt more fat afterwards than a group of hard-out HIIT-doers (also human but probably more smug). One disreputable, non-peer-reviewed hypothesis: all these things are good for you, but the effect of being smug about doing them needs more research.
