The Los Angeles Times just published a new article with research that claims low fat diets were found to beat out low carb diets “handily” for weight loss.
If you’ve listened to me for any significant amount of time, you know that I’m not big on dogma and I’m a huge proponent of intellectual self-defense. I recorded a podcast on The Truth About Grains, Legumes, and Tubers and published a pretty anti-dogma article on The Truth About Carbohydrates. I’ve also been an opponent of ketogenic diets for weight loss.
With that said, I have a lot of problems with this latest LA Times article, starting with the lead paragraph:
It is a central dogma of the low-carb lifestyle: that while avoiding carbohydrates will force the human body into fat-burning mode, any diet that fails to suppress insulin will trap body fat in place and thwart a dieter’s hope of shifting to a leaner, healthier body type.
Actually, that’s not the premise of low-carb diets. It is a premise that’s used by people who are wrong, but it’s not the leading or most widely accepted premise. The leading premise is that low-carb diets help people automatically cut calories through increased satiation.
But researchers from the National Institutes of Health have found that the hallowed creed of Atkins acolytes doesn’t hold up in the metabolic lab, where dieters can’t cheat and respiratory quotients don’t lie.
Keep that bolded part in the back of your mind. It’s going to come in very handy later. For now, let’s take a look at the study design and talk about some issues with it. Then we’ll get to the results and my real-world analysis of what all this means.
Study Design and Issues
Confined for a total of four weeks in an NIH metabolism lab, research subjects (19 obese adults) got equal calories in each condition (low carb, low fat, each for two weeks).
The subjects in each condition also had equally scant opportunities to cheat, shave or misremember what they ate. Night and day, machines measured not only how much fuel their bodies were burning, but what kind of fuel.
Right off the bat, there are some major issues with this study design.
- The sample size is very small. 19 people is not enough for a study of this magnitude. As demonstrated in our podcast, Eating Chocolate for Faster Weight Loss, the smaller a sample size is, the more room there is for random errors and confounding variables to skew the results. There’s also more room for blatant manipulation by the “researchers.”
- I’m not going to pay $31.50 to access the complete research paper to look for other issues, but it’s troubling that the synopsis of the research doesn’t mention the ratio of men to women, nor does it say if they balanced age and gender across the the treatment groups. Obviously, men and women tend to differ in how they lose weight and women’s weight naturally fluctuates during her monthly cycle. Was this accounted for, and how?
- Two weeks is not enough time to run a study like this. On most diets that cut out processed foods, the initial weight loss—and this is especially true for low-carb diets—is going to be water weight.
- There is no mention of the food quality or types of food given. What exactly where these participants eating? That’s very important information that is not disclosed.
- There seems to be no regard for health in this study (or any study like it). I repeat myself every single day: a healthy body comes from a healthy environment. There are many ways to lose weight. Very few are healthy or sustainable. No blood markers were taken and re-checked (not that enough time had passed to do so). Why was health not a goal of this study? Who cares about weight loss if it isn’t healthy?
- What were the movement protocols of each group? How did they rate their sleep and was their sleep interrupted during the study (it says they were monitored by machines night and day)? None of these factors seem to be accounted for.
- The participants did the two protocols back to back. This is not an advisable strategy for getting accurate results.
I’m not sure what to make of the headline the LA Times is using because it doesn’t seem to align well with the results of the study…
In the end, the obese subjects lost weight regardless of which diet they were on (and low-carb dieters lost a little over a pound more than did low-fat dieters over two weeks). But obese subjects on a low-fat diet lost more body fat than did those on a diet low in carbohydrates.
Remember, I’ve already said that two weeks isn’t long enough for this. The extra pound lost on low carb dieting is probably from the excretion of more water weight. This is typical of low-carb diets.
The major issue here comes in the next statement:
The differences were barely perceptible over a subject’s two-week stay in each of the two diet conditions. But the study’s authors devised a computer model and projected that over six months, subjects who stuck with a low-fat weight-loss diet would lose 6.5 pounds of body fat more than those who adhered to a diet that restricted carbs.
You don’t have to be a rocket surgeon to realize that if you take two weeks of bad data and extrapolate it out to six months, it doesn’t magically become good data.
There’s another issue here. An if. And it’s a big if. “Subjects who stuck with a low-fat weight-loss diet would lose 6.5 pounds of body fat more than those who adhered to a diet that restricted carbs.” The reason low-carb diets have become so popular is because they’re exponentially easier to stick with than low-fat diets are.
Guess what? If you can stick with not eating anything for days on end, you’ll lose a ton more weight than on either of these diets. But who can do that? Who would want to do that? If it’s not sustainable, why are we talking about it?
That brings us back to something that was said early on: “the hallowed creed of Atkins acolytes doesn’t hold up in the metabolic lab, where dieters can’t cheat and respiratory quotients don’t lie.”
Someone else made the metabolic ward argument on my Truth About Calories article a while back. Here was my response…
It’s pretty straightforward. Who cares what happens in a metabolic ward? My premise is that people want a body and LIFE they love. Trying to mimic life in a metabolic ward will get you a body you love and a life you hate.
The article goes on to assault the straw man they created in the beginning, with a new twist:
“Furthermore, we can definitively reject the claim that carbohydrate restriction is required for body-fat loss.”
Who made the claim that carbohydrate restriction is required for body-fat loss? Nobody. Nobody who is relevant has made that claim. These “researchers” are arguing against ghosts.
In the war of words between low-fat zealots and the carbohydrate-averse, these findings are a small but significant victory for proponents of reduced-fat diets.
I wouldn’t say that’s the case at all. This study is a complete mess based on false premises and bad data. And that’s coming from someone who isn’t a proponent of either camp. There are times where I think consuming less fat would be beneficial and there are times where I think consuming less carbs would be beneficial. 99% of the time, though, I think people are better served thinking about more relevant things.
“Our study suggests it’s probably the calories in a diet that matter much more than the carbohydrates or the fat,” Hall said. Getting those calories down–and keeping them down for the long haul–is the key challenge for dieters, he added.
No way? You mean The Law of Thermodynamics is the fall-back explanation? Brilliant. Wasn’t that the argument I made in the beginning (and in this video), that low carb diets help people cut calories through increased satiation?
If that’s the case, and the researches agree, then this should be a study about which type of diet is more sustainable long-term. Maybe this is a sign that they didn’t really care about efficacy or your success, but only about proving their initial point? Either way, toss this study into the pile with all the others. It’s trash.
Founder of Rebooted Body and host of The Rebooted Body Podcast. Kevin helps men and women finally get a body and life they love with his unique blend of real food, functional movement, and psychology. To work with him personally, choose a program.