Are Any of the "Named Diets" ACTUALLY Better Than the Other Ones?
Chances are you have never heard the name Dr. Gordon Guyatt, but he has had more of an impact in your life than you realize. A couple decades ago Dr. Guyatt was among a team of researchers who laid out the guidelines for what would eventually be referred to as "evidence based." Today evidence based has become a catch all buzzword in the media, but the term actually has significant meaning. In healthcare if you are making a recommendation based on evidence, that generally means that it has been studied in randomized trials against control groups and/or placebo in large and diverse populations of patients. Then, after enough of the studies have been performed they are put together in the form of a systematic review and meta analysis to have an overview of ALL relevant data. After significant analysis and systematic review comparing all the data and variables we can make recommendations based on what the papers tell us.
In 2014 and 2020 Dr. Guyatt published two meta analysis looking at the effects of the "named diets" on both weight loss and macronutrient content. The 2020 study was titled "Comparison of dietary macronutrient patterns of 14 popular named dietary programmes for weight and cardiovascular risk factor reduction in adults: systematic review and network meta-analysis of randomised trials" and the 2014 study was titled "Comparison of weight loss among named diet programs in overweight and obese adults: a meta-analysis."
The 2014 study examined 121 clinical trials of 14 different named diets and included data collected on 21, 942 participants. Not too bad of a sample size. This particular study looked at macronutrient content of different diet patterns and their effect on cardiovascular markers and weight loss. Despite their being differences between the different diets in the study, the impacts were relatively small when compared to each other and had very little statistical significance (meaning the differences could have potentially happened by accident). The overall conclusion of the study was that all the dietary patterns in the study produced favorable effects on cardiovascular markers and weight loss, and that none of the individual diets significantly outperformed the other.
The 2020 study was a meta analysis of 59 different papers that were written on 48 different clinical trials with 7286 participants. This paper examined different "named diets" and classified them according to macronutrient content (low carb like atkins, paleo, keto versus low fat diets such as vegan, mediterranean, etc). Just like the previous study mentioned, there were variations between individual diets but, once again, they failed to reach a level of statistical significance.
What do we take away from this?
First and foremost, controls are very important in a study. Time and time again, studies of the "named" diets which claim to show superiority over other diets usually utilize very weak control groups. When we compare all of the diets to each other as well as to isocaloric control groups they generally perform the same. Here is what I mean: if we did a study investigating the effects of a south beach diet compared to standard American diet, but both groups in the study ate a tightly controlled 2000 calories a day, we would see very little difference between the study group and the control group. Likewise, if we compared a south beach diet to a paleo diet and both groups only consumed 2000 calories per day we would again see very little difference between the two diets. Many times when we hear that "X" diet is superior to "Y" diet, we must look at how the study was performed.
The second lesson from this is simple. Nutrition science is very weak. There is very little high quality evidence related to ANY of the "named" diets. The two studies we are talking about in this article looked at data collected on nearly 30,000 people, yet both of the conclusions in the papers talk about the relative lack of strength in any of the studies. This is because A) nutrition studies are hard to put together and carry out. There is a lot to control for! B) Most "studies" people point to when arguing nutrition are epidemiology studies. Epidemiology studies do not show causation, only correlation (many times those correlations are very weak).
The last takeaway, calories matter more than the name of the diet. We already talked about controls, but the most important control in a nutrition study is total calories in the diet. When the diets are studied against each other and calories are controlled for, there is very rarely a significant difference between the outcomes of the diets (ie. 2000 calories of paleo vs 2000 calories of keto). I've seen many people jump in head first to a vegan diet, keto diet, atkins, or *insert diet here* but continue to consume excess calories and wonder why they are A) not losing weight or B) still gaining weight. Calories matter.
So, what do we do about it. The Be Well Chiropractic Primal Health nutrition recommendations are quite simple: Eat real food, keep calories *SLIGHTLY* restricted for the rest of your life (eat less than you burn), and develop a diet that you can stick to for life without relying on supplements (if your diet requires supplementation it isn't a complete diet).
The most important factors which determine long term success with proper eating isn't the name of the diet, or how many people promote the diet on instagram, or even whether or not the government recommends it (have government dietary guidelines ever been good for individual health?). The most important factors are sustainability and adherence, *SLIGHT* caloric restriction, and food choices that lead to improved macro and micro nutrient content.