Rude food by Vir Sanghvi: Fads vs diet facts
All diets go through a similar lifecycle. Somebody tells you about a great new diet. At first you are skeptical but then you meet people who have been on the diet and have lost so many kilos that you become convinced that there must be something to the diet.
Somebody else recommends a best-selling book about the same diet. You are impressed and enthusiastic even as doctors advise you to steer clear of what they call ‘fad diets’. They repeat that you should just eat less, have three meals more regularly and take more exercise.
You dismiss the medical opinion as being out-of-touch and fuddy-duddy. Then science gets in on the act and spoils the fun. Studies are published that show that the diet is bad for you/does not work/leads only to short-term weight loss. You pause for thought and then somebody else comes along with the next trendy diet and you move on.
The cycle then repeats itself with the next diet.
So far, the craze for intermittent fasting has not yet been through the full diet lifecycle. We are still at the stage where doctors are warning against it (“You shouldn’t keep your stomach empty for so long” etc.). But these warnings are being largely disregarded and people continue to tell stories about miraculous weight loss through intermittent fasting.
Last week, the craze for intermittent fasting moved into the next phase of the diet lifecycle. Till now, there has been little scientific research into intermittent fasting. It has all been anecdotal.
Typically, all research into diets falls
into one of two categories. There is the how-it-works school of research. This examines the biological reasons for why a diet makes the body shed weight. For instance, some research looks at insulin release in the body, its effects on weight loss and whether certain foods can affect insulin levels.
Then there is the does-it-work kind of research. In this kind of study, a group of volunteers is split into two. Half of the group goes on the diet. And the other half (the so-called ‘control’ segment) eats normally. If the control segment does not lose as much weight as those on the diet, then it is reasonable to believe that the diet does cause weight loss.
So far, there has been very little work on intermittent fasting. But now, The New York Times reports that a rigorous study of intermittent fasting has been published in JAMA Internal Medicine, a well-respected journal. It is a does-it-work study, led by a cardiologist at the University of California.
A group of 116 overweight adults was split into two. The control group ate three structured meals daily while the other group practised intermittent fasting, eating only between noon and eight pm so that they fasted for 16 hours. The study went on for three months.
Its results surprised its lead doctor, who practised intermittent fasting himself and believed in it. The fasting group lost an average of two pounds over three months. This is much less dramatic than the weight loss claims made for the diet. Worse still, the control group lost nearly the same amount: one and a half pounds.
So, all that intermittent fasting achieved over three months was the loss of half a pound.
The study checked metabolic markers for some (but not all) of the participants. Even among those who did lose weight on the diet (the two-pound figure is an average for the whole fasting group so some did lose more; and some lost less) there was little or no improvement in their metabolic markers. And 65 per cent of the weight that was lost came from muscle. (All diets cause muscle loss but it’s usually under 35 per cent of the total weight lost.)
The doctors reluctantly conceded that intermittent fasting did not work and the lead doctor, who had been a believer, went back to eating at normal times himself.
We still don’t have a how-it-works (or in this case perhaps, how-it-doesn’t) model for intermittent fasting but many doctors are skeptical of the central claim advanced for it: that if the body is deprived of nutrition for 16 hours, it will burn fat to make up for the deprivation.
Doctors are more favourably disposed towards two other explanations. The first is that people who have to eat all their meals within eight hours generally eat less. At first, they are excited to be told that they can eat whatever they like but as time goes on, they end up eating less. So, say some doctors, intermittent fasting is just another way of calorie-controlled dieting. The early gains come from water loss, which is often a routine feature of most diets. And then the weight loss comes slowly as it does with calorie-based diets.
A second medical explanation is that eating earlier in the day enables the body to metabolise food more quickly and more efficiently. According to this view, by restricting people from eating after eight pm, intermittent fasting stops them from consuming food too late in the evening. But this is a controversial view, which many scientists dispute.
(In any case, the whole eat-early-in-the-day theory goes against intermittent fasting, which encourages you to skip breakfast.)
The truth is that no scientist has been able to come up with an explanation for why intermittent fasting will make the body shed weight. On the other hand, all of us have heard stories of people who have shed kilos by following an intermittent fasting regime.
If the craze continues, then there probably will be more studies involving longer durations and larger groups of participants. But if you have tried intermittent fasting and found that it causes more acidity than weight loss, don’t worry too much. At the moment, science is on your side.
If, on the other hand, you have tried it and found it works for you, then don’t give up. The general rule of thumb is that soon after one study appears, another one comes out claiming to demonstrate the exact opposite.
The truth is that there is no scientific consensus on how to lose weight. And scientists are now coming around to the view that there is no one-size-fits-all method. Different people gain and lose weight at different rates for different reasons.
So, always read up on the science. But never forget that you know your own body better than anyone else.
The views expressed by the columnist are personal
From HT Brunch, October 11, 2020
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