The past two months saw an evidence-based takedown of two popular fad diets. The first was intermittent fasting, or IF. IF has been proclaimed to be an easy way to cut calories and train your body to burn more fat and reduce weight. The basic premise of this diet is to fast on and off as a strategy to cut calories. In the most impressive study to date published in JAMA Internal Medicine, patients afflicted with obesity were assigned to 1 of 3 groups for a year: alternate-day fasting (25% of calorie needs on fast days; 125% of calorie needs on alternating “feast” days); daily calorie restriction (75% of calorie needs every day); or no intervention.
After one year, weight loss between the IF diet (6%) and the caloric restriction diet (5.3%) was the same. There is nothing special about IF. What matters in dieting for weight loss is calorie reduction. It’s also worth pointing out that the IF diet had a significantly lower adherence rate, meaning that is was more difficult to follow.
In the “conflicts of interest” section of the published manuscript, the senior author acknowledges that she received an advance from a publishing company for a book called “The Every-Other-Day Diet: The Diet That Lets You Eat All You Want (Half the Time) and Keep the Weight Off.” A first glance, I thought this was great. Transparency in science is something scientists need to work on. Considering the author has shown that IF results in low adherence and is no different than reducing calories, she won’t mislead the public by publishing a book touting IF as the next great diet plan? Upon closer inspection, this book was published in 2013. In fact, it has its own website with the statement “This is a revolutionary, science-proven, easy-to-follow diet.” We now know IF is not revolutionary in the sense that it does not offer better results vs. simply restricting calories, and it is not easy-to-follow.
Putting the cart before the horse is a consistent issue with the blending of science, media-hype and the desire to sell books.
The second diet is Gluten-free, which was popularized by the fear-mongering and now debunked novel “Wheat Belly,” also received some bad news this month. Two independent reports have concluded that gluten-free dieting may in fact increase the risk for cardiovascular disease and obesity.
Gluten is a protein found in wheat, rye, and barley. In individuals afflicted with a disease called celiac disease, gluten causes intestinal inflammation and increases heart disease risk. This disease effects approximately 1% of the population.
Over the past few years there has been a wave of people subscribing to a gluten-free diet who do not have celiac disease. Estimates from the Government of Canada put gluten-free dieting (or “gluten avoidance”) at around 22% of the population.
A study published in the British Medical Journal, which included 64,714 women and 45,303 men, made the following conclusion; “Long term dietary intake of gluten was not associated with risk of coronary heart disease. However, the avoidance of gluten may result in reduced consumption of beneficial whole grains, which may affect cardiovascular risk. The promotion of gluten-free diets among people without celiac disease should not be encouraged.”
In other words, by avoiding gluten, people reduced their intake of healthy whole grains, which then increased their risk for cardiovascular disease. It’s not necessarily that avoiding gluten is bad, it’s that not eating a balanced diet is bad.
In a separate study presented at the European Society for Pediatric Gastroenterology, Hepatology and Nutrition Conference, gluten-free products were found to be more energy-dense than their conventional counterparts. These results suggest that gluten-free dieting may lead to unnoticed increases in caloric intake, which we know is a critical variable for obesity risk.
No doubt there are limitations to each of these studies, however I think it’s safe to conclude that evidence to support the proposed health benefits of a gluten-free diet is simply not present.
Authors promoting a miraculous dietary strategy for weight loss – even if they have PhDs or MDs as in the above examples – should be heavily scrutinized.
By Brennan Smith, PhD