Monday, 12 November 2012

Weight loss diets: How to separate the fad from the facts

There comes a time in every dietitian’s career (or, more accurately, several times) when he/ she feels ready to give someone a good old-fashioned strangle. This murderous urge is set off by the birth of Yet Another Fad Diet. I have just battled through such a time.

Sometimes being a dietitian can get to your head.
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It all started when I had the bad luck of stumbling upon the Wheat Belly Diet, started and promoted vigorously by a certain cardiologist.

I don’t mean to be nasty, but I’m afraid I have to call quackery with this man. He misquotes journal articles to support his cause, makes things up, and ends it off with an enthusiastic recommendation that you buy his book (no ulterior motives there at all). If I have some time off over the next few days, I can address that diet specifically.

For now I want to talk about fad diets in general, and how we can figure out if it’s a load of rubbish, or if it is really a safe, healthy, effective way of losing weight – in the long term. Because if we cannot sift the bad from the good, we’re setting ourselves up for years of losing/gaining/losing/gaining weight, messing with our metabolism, and possibly even putting our health at risk.

The key to this, my friends, is good, sound, scientific research. Nothing more, nothing less.
Scientific research is what we’re talking about when we put new medications through controlled, rigorous, clinical trials. You cannot just develop a drug and ask everybody to give it a bash. You need to ensure that it is safe, that it works, that it works on a significant number of people, and that there are no short term or long term side effects. Same goes for scientific research with nutrition, and weight loss.

Research should be the foundation of health recommendations.
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Let me make a silly example: Say I stuck 10 people in a room. And as their dietitian, I decide to try them out on a diet of only fruit for a week. And say 7 of them lost weight on this diet – but 3 didn’t. What can we conclude? Well, the vast majority lost weight; evidently, eating only fruit is an effective weight loss solution for most people.

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No. We haven’t looked at what else has been going on – who are these people, their genes, how much exercise they were doing, what were they eating before they came in, what were their portion sizes of fruit, what other illnesses are involved – these are all factors that make a massive difference in anybody’s weight loss. For example, maybe those 7 people simply got diarrhoea from all the fruit and lost weight through dehydration. Maybe those 7 did two hours of jumping jacks every day out of boredom… from being stuck in a room, of course.

In addition, how do we know that these ten people aren’t just a freak group of individuals with a genetic ability to metabolise fruit sugars more than other people? Maybe if we tried the diet on 50 people, we would see that only 9 out of 50 people lost weight – we could no longer conclude that eating only fruits will make you lose weight.

Another concern is, we have only tested these people for a week. How do we know what will happen after a few weeks, months, years? Will they be able to stay with the fruit-only diet? Maybe they’ll start gaining weight, maybe they’ll develop protein and iron and vitamin E deficiencies and die. All because we got excited about results after just one week.

That, dear reader, is where scientific research comes in. Good research painstakingly combs through all the other factors that may have influenced the weight loss, and makes sure that it is only the fruits that are the reason for the weight loss. It also ensures there are enough people involved to be statistically significant – to make sure that we didn’t get these results out of pure chance. And before we can say with certainty that this is a goodie, we need to do prospective studies to ensure that it has no dangerous long-term effects.

So please: I am not saying ignore everything out there. Science is always evolving, new research is always coming up with new information. If cutting out a bit of wheat works for you, have a party with that. But take a good look at it. Go to Google Scholar and see if there has been any solid research done with this diet on humans. No matter how much theory there is behind a diet – “many people are carbohydrate intolerant”, “wheat causes inflammation in many people”, “humans weren’t designed to drink cow’s milk”go look at the real picture, see what actually happens when these diets are tried on a large group of people, in a controlled setting. That’s where we find the truth.

Scrutiny is key.
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If you want to turn yourself into a human lab rat for each new, unproven diet, go ahead. It’s your health, it’s your yo-yoing weight. But I would rather develop a lifestyle to bring me lifelong health and happiness.

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