Eat,fast, live longer

Another interesting (if not yet reliably useful) food/health documentary last night: Horizon's "Eat, fast, live longer" which reported on recent studies suggesting occasional extreme fasting (~50 cals per day for 4 days every few months) or regular (alternate-day) near-fasting (~400 cals per day) could provide major health benefits, even if people ate normally (or even badly) the rest of the time.

(BBC link here, guardian review here)

This is not the first time I've heard of how low calorie intake is linked with longevity, but until now I only knew about people who were (without a lot of human based evidence) living long term with massively reduced energy intakes, which didn't seem very worthwhile, since even if it did make them live longer, reduced their energy levels so much it was debatable whether they were able to live life at all. The recent research however, though presumably arising from the same evidence, suggests that it might not (just) be consistent reductions in calories that brings benefits, but even short term occasional fasts. There seems to be signs that the body enters a kind of 'repair' mode when starving, and the are hopefuly indicators of how this might reduce or even prevent illnesses such as heart disease or stroke.

While I can't comment on the scientific basis (which was admitted to be only new and limited, albeit promising), there are perhaps a few general common sense points that can be made. My own personal 'gut instinct' is that any diet which matches our evolution, has to make sense; hence modern artificially concentrations of sugars,salt, and fat have to be viewed with suspicion. Beyond this though, as incredibly versatile omnivores, it is probably quite hard to work out what our ideal pre-modern diet actually was. It's likely that life was hard, and resources scarce, so it does make sense that it was largely plant based, since presumably hunting was harder and more unpredictable. However, given that we can consume animal meat, and in certain cultures (eskimos) can survive on it, then I would be wary of excluding it altogether, although it might make sense to limit it. So I would think a balanced diet, with emphasis on plants, sounds like a good idea, and have never seen strong evidence against this.

However, leaving aside the type of food, and focusing on the quantity, such a boom-and-bust cycle of nutrition could also fit well with the latest fasting research, since our bodies would have done well to adapt to (and even make use of) such times of shortage. The problem however, as with all neat evolutionary stories, is it is important to keep in mind the arena in which evolution operates, something which might not align well with modern life expectancies. Evolution works on the fitness of the animal primarily until it procreates, and then perhaps for some while after as it supports its offspring/descendants. The problem is, given that ancient man might only have lived till 30 or 40, and heart attacks and cancer are mainly illnesses of later years (perversely rising cancer rates can be a good thing, since indicates a society living longer), it's very possible that there is nothing evolutionary in us to combat them. This doesn't mean there aren't optimum ways of extending our lifespan, but rather that we are inventing them, not re-discovering them. It might be that the issue is not making the machine run as it should, but finding ways to make it run as it could.

However, this then raises the questionas to whether the same approaches fit all stages of life. It could be that in earlier, fitter, more active years one type of diet is optimum (and matches evolutionary history), but in later years a change of strategy is needed. For example I wonder about the link between growth and cancer. Several times recently I have seen evidence about diets which seem to reduce cancer rates, but perhaps also impact normal cell growth. This of course makes sense, since cancer ultimately is excessive growth, so it is logical that what would stop growth normally, would stop cancer as well. But what is far less from clear is whether this is a desirable thing, under normal healthy circumstances. Like constant restriction of calories, could the cure (limited life) be worse than the disease (risk of limited lifetime). It coudl even be the case that in certain stages of life one approach makes sense (run body at full power, albeit putting under stress) but at other, older, stages another is appropriate (scale back to focus on preservation, not performance). Ultimately of course a balance is needed, but making the judgement needs more evidence and consideration than just jumping on the latest diet that shows (even if verified) improvement in one range of parameters. Better cholesterol, lower glucose levels, are good things, but what else changes, and what are the overall effects? From what I remember, the studies for example (as those mentioned in the film forks over knives) involved people who were already unhealthy - older, obese etc. It is one thing to provide a solution for people who clearly have a problem, it is another to show that solution is applicable to preventthat problem in the first place.

in the spirit of balance and moderation, I therefore think fasting diets sound so extreme that is would be prudent to wait for more evidence. One probably reliable maxim that can be taken is overconsumption, even without obesity, but of meats etc. might be a problem. So probably a safe bet, to limit, but definitely not exclude, meats, ramp up plant elements, and overall keep consumption down and in line with activity. Still, who knows how this research will develop, and all thought about food, is valuable food for thought.