The BBC showed a Horizon program recently in which it extolled the benefits of the so-called 5:2 diet, the on-off, alternating fasting diet. Apparently, scientists are “uncovering evidence that short periods of fasting, if properly controlled, could achieve a number of health benefits”. The show was presented as these often are by TV doctor Michael Mosley and as is often the case, he tested the diet on himself.
In the close of an article about the show, Mosley says: “I was closely monitored throughout and found the 5:2 surprisingly easy. I will almost certainly continue doing it, albeit less often. Fasting, like eating, is best done in moderation.”
So, despite apparently being rather convinced, it appears that he’s not actually going to persist with it…
Anyway, that’s not my biggest problem with this kind of TV. One thing that always worries me about these kinds of programs, is that the presenter puts him or herself into the position of experimental subject. I don’t think you can be both experimenter and the experiment yourself in this kind of research. You need lots of people and controls (people who don’t get the intervention) so you can randomize who does and doesn’t take part and see what effect it has. If it’s just you, then there no one to compare your results with.
Moreover, in the Mosley 5:2 example, hasn’t he done lots of exercise and dietary modifications previously for other TV programs? He enthused about a short-burst exercise regime a while back too, although the actual metrics on his health didn’t really show much of an improvement at all. Apparently, on the 5:2 he did lose weight, but how are we to know that’s not down to his previous exercise and dietary regimes?
I have a friend who is trying the 5:2, he’s not lost any weight yet, but thinks it might be a good thing to be doing, which is fine. If he feels healthier because of it and is happy, then perhaps it doesn’t do any harm. If he loses a few pounds in the course of the diet then that’s great too, but he needs to watch out for metabolic bounce back. If he stops the 5:2 he might find his hunger levels have risen from what they were before and he ends up eating more on average than he did. This seems to be an inherent risk in low-calorie or calorie-restricted dieting. That said, there was some evidence published earlier this year that hinted the yo-yo effect of dieting may not be as hazardous as was once thought.
It’s very hard to know about dieting and life expectancy. After all, the final data doesn’t come until you’re dead by which point it’s too late. It seems, however, that over-indulgence and excess calories makes people heavier and being heavier puts extra physical strain on your heart, blood vessels, kidneys etc. Excess sugar can affect the functioning of your pancreas leading to diabetes which then damages your tissues. Fats and cholesterol can form layers of waxy gunk inside your organs and arteries and lead to blockages that increase the risk of heart attack and stroke.
But, there are overweight people who never develop cardiovascular disease or type 2 diabetes, live long and prosper and there are skinny marathon runners who need bypass surgery in middle age and die prematurely.
Despite what the lifestyle magazines and those selling diet and exercise self-help books say, we really don’t know what is truly good and bad for us. It’s not likely to turn out that pounds of lard and plenty of cigarettes will ever prove to be a good thing (although nicotine seems to reduce the risk of Parkinson’s disease). There are even disadvantages to eating a lot of fresh fruit in terms of rotting your teeth and giving you gut rot and indigestion. Dental and gum infection has been linked to heart disease while chronic digestive problems for some people might not only cause discomfort but may turn out to be a risk for esophagal and colon cancer. Who knows? The evidence can swing both ways.