By Jane McCredie. This article first appeared on MJA Insight 5 September 2016.
“DOES it have carbs in it?” one of the personal trainers from my gym asks in a local cafe, his face screwed up with disgust as though somebody has suggested he eats maggots.
Actually, he’d probably be happy to eat maggots if you told him they packed a protein punch.
Diet fads come and go, but one constant seems to be their reliance on miracle foods that will transform you into a perfectly toned version of your current self, combined of course with the demonising of other foods that must be avoided at all costs.
Once upon a time, the chief enemy was fat. These days, it’s carbohydrates.
But is there any evidence to support either claim or the obsessive, sometimes ludicrous, eating habits they might encourage? (Yes, Paleo diet, I’m looking at you.)
Not according to this 2014 meta-analysis of 48 trials published in the Journal of the American Medical Association.
“Significant weight loss was observed with any low-carbohydrate or low-fat diet,” the authors concluded. “Weight loss differences between individual named diets were small.
“This supports the practice of recommending any diet that a patient will adhere to in order to lose weight.”
In other words, what you have to do if you want to lose weight is pick a diet, any diet, and stick to it.
But there’s the rub. Long term adherence to a restricted diet is notoriously difficult.
While the JAMA meta-analysis found significant weight loss over the first 6 months (around 8 kg on average, regardless of diet type), participants started to put the weight back on after that.
If different dietary approaches are all pretty much equally effective in the short term, and equally ineffective in the long term, what does that mean for people struggling with their weight and the clinicians who advise them?
We might be able to get a clearer view if we put an end to the “diet wars”, according to two obesity experts writing in the Lancet last week.
“Claims made for the superiority of one diet approach over another are based on small short term differences that are not clinically meaningful”, they write.
So, rather than conducting endless trials in an attempt to bolster the position of one diet over another, we could instead try to work out how to design tailored diets for individual patients along with strategies to help them stick to them.
“[We need to] improve our understanding of the real world considerations that impinge on patients’ abilities to sustain healthy dietary changes, such as those wrought by the food environment, socio-economic factors, cooking skills, job requirements, medical comorbidities, caregiving responsibilities, and many more,” they write.
As the authors of the JAMA meta-analysis put it, the ideal diet is the one an individual will adhere to in the long term.
There’s a lot of money to be made from a successful diet fad, and all the merchandise that goes with it, so the celebrity chefs and internet nutritionists aren’t going to let up on their extravagant claims any time soon.
But perhaps researchers could shift their focus, as the Lancet authors suggest.
“Fewer resources should be invested in studying whether or not a low-carbohydrate diet is marginally better than a low-fat diet, or whether intermittent fasting provides marginally better short term outcomes than a so-called Paleo diet,” they write.
“Crowning a diet king because it delivers a clinically meaningless difference in bodyweight fuels diet hype, not diet help. It’s high time we started helping.”