For those of you, please read the comments and social media commentary. Then you will realize that many people have his second objection.
2. Conservation of energy does not apply to the human body! It’s hormones or mass or something, and calories are just an invention of the processed food industry.
For such people, I recommend consulting a physicist.
Now, that’s an interesting discussion.
3. Yes, calculating calories in vs. calories out should work, but low-carb diets affect both sides of the equation, so dismiss the effect (as I did) as real but small. You can’t.
The macronutrient content of your diet influences how many calories you burn (because people metabolize fat, carbohydrates, and protein differently) and how many calories you take in (because some foods are more satiating than others) Everyone agrees it’s possible. The disagreement is over the magnitude of the change, particularly with regard to low-carbohydrate diets. So let’s talk about it.
First, a low-carb diet affects the calorie-burning part of the equation. The logic is that less carbohydrates means less insulin, and since insulin is essential for fat storage, you’ll be burning calories instead of storing them. It’s a plausible and testable theory. Put people in a controlled environment, give some people a low-carbohydrate diet with the same number of calories, give others a high-carbohydrate diet with the same number of calories, and see who loses more weight. Let’s.
Then there’s the calorie intake side of the equation. The theory is that low-carbohydrate diets make you feel fuller, making it easier to reduce your calorie intake. That’s also a plausible and testable theory. Assign people different types of diets without calorie restriction and see who loses more weight.
Fortunately, both of these tests have been completed, so let’s take a look at the evidence.
Ah, the proof. This is a tricky wicket because you can find “evidence” to support almost any conclusion you want to draw. And if you frequently engage in diet discussions, you’ve probably seen the long list of evidence supporting the low-carb theory.
When you see a list like this, you should ask questions like: Please prove it something is true or discover whether That’s true? My job as a journalist is that I’m as susceptible to confirmation bias as the next guy, so I do my level best to examine all the evidence. I’m sure he’ll be honest.
First of all, let’s take in calories. If you really want to know if you’re eating less on a low-carb diet, park your car at: pub med, a repository of magazine articles. I will focus on meta-analysis because its job is to assess the preponderance of evidence. Using “low-carb diet weight loss” as the search term and restricting the results to meta-analyses yields 61 results. I read everything that seemed relevant.
They were all saying the same thing. This was reassuring since they were primarily meta-analyzing a combination of the same set of studies. In fact, in short-term trials (less than a year), low-carbohydrate diets outperform other diets by several pounds (less than 10 pounds). Examples include: Chawla, 2020; Monsour, 2016; and Nordmann, 2006. However, two meta-analyses found that people lost slightly more weight on a Mediterranean diet than on a low-carbohydrate diet. (Ajara, 2013; Pan, 2018).
After a year, most of the low-carb benefits disappear. Some meta-analyses have found small benefits, but only a few pounds (Bueno, 2013; Tobias, 2015). Some people have no benefit at all (Rafiura, 2022; silver ii, 2022; Naude, 2014; Hu, 2012).
In my opinion, low-carbohydrate diets are easier to maintain in the short term. Removing all high-calorie, easy-to-eat foods (bread, pasta, rice, baked goods) from the diet is effective for many people, at least for a while.And there it is some evidence Very low-carbohydrate diets (ketogenic diets) are more satiating than other diets, but Fascinating but short-term research The results showed that people on the keto diet ate nearly 700 more calories per day than those on a low-fat diet.
But in the long run, the only thing that matters about a diet is whether you can stick to it, and studies have shown that low-carb diets are no better than other diets in that regard.
Let’s move on to the calories burned part of the equation. Do people on low-carbohydrate diets lose more weight for the same number of calories because their bodies expend more energy?
This is not the case in tightly controlled trials in which subjects are fed isocaloric diets with varying macronutrient composition. Although there have been many such studies, we have not found a single study in which carbohydrate content made a difference.
Back in 1977, small study They compared a 14-day diet containing 70 percent carbohydrates to a diet containing 10 percent carbohydrates. The researchers found that the participants lost more weight on the low-carbohydrate diet, but regained it as soon as they stopped eating, indicating that this was the expected water loss on a very low-carbohydrate diet. Ta.longer study In 1992, researchers tested diets ranging from 15 percent to 85 percent carbohydrates and found no difference in the energy needed to maintain weight.
2015, National Institutes of Health researchers kevin hall found that Participants who ate a low-carbohydrate diet (53 grams per day) burned less fat than those who ate a low-fat diet (89 grams per day).and in 2016Hall found that while the ketogenic diet does lead to more energy expenditure, that small difference does not translate into fat loss.
I wanted to make sure I wasn’t missing anything, so I turned to David Ludwig, a professor of nutrition at Harvard School of Public Health and a prominent proponent of low-carbohydrate diets.He pointed out to me (via email) that his meta-analysisThis is total energy expenditure (TEE) rather than weight loss, indicating that low-carbohydrate diets do lead to increased energy expenditure, but the maximum effect does not appear until about 17 days later.
Hall and Ludwig see things very differently, disagreeing about how TEE should be measured and how these studies should be interpreted, but their interactions reflect how scientific disagreements are handled. I think it’s a great example of what should be done. Hats off to both.
Mr. Ludwig hangs his hat on TEE, which he tells me is an “instant fix” that doesn’t require you to wait for it to show up as fat loss. However, as a hall, wrote, TEEs may not be summed, especially in outpatient studies. One study For example, they found that low carbohydrate increased TEE by 200 to 300 calories per day, but even though their average weight remained stable, they reported taking in 480 fewer calories than they expended.
I would venture to suggest that the gold standard for weight loss trials is actual weight loss. And if the amount of excess energy expended on a low-carbohydrate diet is high, we would expect it to show up in the next stage. Loss of body weight (more specifically fat). And it’s not.
Ludwig explained this to me as follows:[ly] Confused by temporary effects, it is so weak that it is virtually meaningless. ”
A three-month study of hospitalized patients whose diets were carefully controlled would probably be prohibitively expensive, but I’ll end my discussion here. Yes, a low-carbohydrate diet may indeed increase energy expenditure, but the amount is so small that the signal won’t rise above noise until at least three months.
I’m all for low carb diets. They eliminate large groups of foods that most of us should probably eat less of, and some people find ways to continue eating them long-term. But there is no metabolic magic.
You lose weight on a low-carb diet because, drumroll please… you eat less.
