There are more than 1000 diet books available and more popping up on Amazon every month. These are the “popular diets.” The newest fads. The new diet that everyone is talking about and promises to fix it all.
In medicine I’ve learned to be skeptical when there are a thousand treatments for a condition. The reason a condition may have a thousand treatments is that no single treatment is proven to work the best.
This may also be the case with popular diets.
In the Journal of the American Medical Association (Dansinger et al 2005) researchers compared four of the most popular diets; the Atkins, Ornish, Weight Watchers and Zone Diets for weight loss and heart disease risk.
They randomly sorted 160 participants into 4 groups (40 each) for each diet type and educated them about their new diet using small group sessions. The participants were also given written materials and cookbooks to follow.
All participants were asked to take a multivitamin daily and exercise for at least 60 minutes per week. After 2 months the participants were asked to continue the diet on their own based on their own interest in it.
The researchers measured participant’s weight, waist circumference, blood pressure, cholesterol levels and C-reactive protein levels (a general measure of inflammation) and followed them (and their biostatistics) for a year.
I know what you are waiting for. Which diet proved to be the best?
Let’s settle it for good.
Unfortunately, the answer will disappoint you.
There were NO winners.
All 4 diets resulted in modest weight loss (between 3-6 kilograms) and there were NO difference in weight loss between the diets.
Cardiac risk factors (blood pressure, cholesterol profile, C-reactive protein) also improved to varying degrees with all of the diets. The amount of weight loss, not necessarily the type of diet, predicted the improvement in cardiac risk factors.
Adherence was poor amongst all the diets and got worse over time (42% dropped out by the end of the year). There was no strong proof that it was easier (or harder) to follow any particular diet. At the end of the year adherence trended worse for the Atkins and Ornish diets, but this was NOT “statistically significant” (may have just occurred by chance alone).
Reasons cited for quitting any of the diets was that the diet was too hard to follow and did not provide enough weight loss.
Now here is where it gets interesting.
There was a strong association between the adherence to a diet and weight loss.
Let me be clear about this.
There was NO difference in weight change BETWEEN the diets. Whether it was Atkins, Ornish, Zone or Weight Watchers; they all had roughly the same weight loss. Adherence (to any of the diets) did predict weight loss. The more adherence, the more weight loss across all diet types.
What this means is that the type of diet made less difference than whether a diet (of any type) was simply followed.
So, why do diets fail?
They are not followed.
The word “diet” is derived from classical greek “diaita” meaning “way of life.” How do we make healthy dietary changes a way of life?
The real questions to ask are why do we struggle to follow diets? What are the barriers to success? Why do we give in, especially over the long term? How do we stay motivated to stay on track?
Or
Are diets inherently flawed to begin with?
So, we may be asking all the wrong questions.
What type of diet is the best?
I suppose the one that gets followed.
The Evidence: