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There are so, so many diets out there. Some are low in fat, others are low in carbs. Some involve special foods, others tell you to avoid them. So what's the best diet for you? Watch and learn!

Most of the data for this episode comes from this recent paper in JAMA: http://jama.jamanetwork.com/article.aspx?articleid=1900510

John Green -- Executive Producer
Stan Muller -- Director, Producer
Aaron Carroll -- Writer
Mark Olsen -- Graphics

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There are so so so many diets out there. Some are low in fat, others are low in carbs, some involve special foods, and others tell you to avoid them. So what's the best diet for you? That's the topic of this week's Healthcare Triage.

[intro]

A couple of weeks ago on health care triage news I told you about a study that compared a low carb diet to a low-fat one.
  The low carb diet performed better on almost every metric, which exasperated me because many organizations continue to promote the idea that low-fat is the best way to go.

We should recognize, though, that the levels of "low carb" on this diet were really low. People kept their carb consumption to about 30% of calories a day, and they were eating a reasonably low number of calories. And they kept this up for a year! Most diets out there, even the low carb ones, don't hit that level.

Initially, this study was focused on a lot of outcomes besides weight. And let's be honest: the reason most people watch this video will go on a diet is to  lose weight. So let's talk about that.

There have been a lot of studies comparing named diets. So many that a bunch of researchers were able to conduct a meta analysis of these studies--a battle royale, if you will, of named diets.

So: to the research!

The authors of this meta-analysis reviewed the medical literature for any randomized controlled trials of obese or overweight adults who were placed on popular self-administed named diets for at least 3 months. The main outcome of interest was weight loss at 6 and 12 months.

For those of you who watched the systematic review and meta-analysis videos, and you really should have, the researchers identified 20,835 potential studies. Of these, 889 were promising enough to merit a full review. Of these, 59 met criteria, and they described 48 randomized controlled trials of 11 branded diets.

These were grouped into 3 diet classes. The low carb diets generally kept carbohydrate consumption below 40% of calories, protein consumption below about 30% of calories, and fat from 30-55% of calories.

The moderate macronutrient diets kept carbs to about 55-60% of calories, protein to about 15% of calories, and fat between 21 and 30% of calories.

Finally, low fat diets kept carbs at around 60% of calories, protein to 10-15% of calories, and fat below 20% of calories.

For the record, the 2010 Dietary Guidelines for Americans recommends that adults get 45-65% of calories from carbs, 10-35% from protein, and 20-35% from fat. So the moderate macronutrient diet is closest to that.

Low-carb diets included Atkins, South Beach, and the Zone diet. Moderate Macronutrient diets included Biggest Loser, Jenny Craig, Nutrisystem, Volumetrics, and Weight Watchers. Low-fat diets included Ornish and Rosemary Conley. Two diets defied grouping: the LEARN diet was analyzed as both a low fat and a moderate macronutrient diet, and the Slimming World diet fit no definitions at all.

Let's start by talking about diet classes. First thing you should know is that all of these diets, and I mean all of them, were better than nothing at six months.

The low carb diet performed better than all of the others, with median
six-month weight loss at 8.7 kilograms, or about 19 pounds.Although the low fat diet was so close at 8 kilograms, or 17.6 pounds, that the difference wasn't statistically significant.

Another way of looking at it was this: at 6 months, the low-carb diet had an 83% chance of having the best performance. The low-fat diets had a 17% chance of being the best.

At one year, things changed up a bit. In general, weight loss was rarely better at 12 months than it had been at 6 months. Low-carb and low-fat diets were still best, but now low-fat diets were just a tiny bit better. The difference, though, was 20 grams.

Yeah, you heard me right. 7.27 kilograms for low-fat, and 7.25 kilograms for low-carb. For the metrically challenged, that's 16.03 pounds versus 15.98 pounds.

In other words, at one year, the low-fat diets had a 50% chance of being best. The low-carbs had a 48% chance at being best, and the LEARN diet had a 2% chance. So basically a coin flip between low-carb and low fat.

But how about the individual name diets? At six months, the best performing was Atkins, at 10.1 kilograms, followed by Volumetrics at 9.9 kilograms, and Ornish at 9 kilograms.

I'm gonna talk really slowly here, so you can look at at this nice chart Mark made to see where your favorite diet fell in the spectrum. Remember, they all worked, but to different degrees.

At twelve months, though, the differences were not nearly as big. Here's that chart. The best-performing diet was a generic low-fat diet. Atkins lost its top spot by quite a bit, and others like Jenny Craig and Weight Watchers pulled into the pack.

There were no significant differences in serious adverse events in any of these trials, although they were only reported in five trials, all of them were Atkins trials, which seems unfair, because why would you assume that only the Atkins diet could lead to problems? Anyway, of those five, only one found any issues at all, and they were all minor.

So what do you take from this? Anyone hoping for a silver bullet should be totally disappointed. There isn't one. The one thing all of these diets have in common is that they involve calorie restriction in some way. Even in the Atkins studies, men consumed 1400-2200 calories, and women consumed 1200-1600 calories. That's less than most people eat. Generally, when you eat fewer calories, you lose more weight.

There are plenty of caveats here. It's possible that the types of carbs and the types of fats consumed here made a difference...maybe. It's possible that the effects of exercise and behavioral support, like with meetings, could make a difference...probably.

So here's the truth: the best diet for you is likely the one you're going to keep. If the idea of a low-carb diet appeals to you, go with that one. If low-fat foods appeal to you, go with that one. It really doesn't seem to matter that much.

The ideal diet is the one you're going to adhere to. This is especially true in the long term, as almost all of these diets had weight gain in the second six month period.

The good news is that almost all of them work. There's hope. You just need to find the one that works for you. And then you really really need to stick to it, for a long, long time.

[outro]