Do you wonder about the effectiveness or science behind the Low-Carb approach to eating? It seems like it might be hard to fool the body for a long time. But many researchers have studied this and the article below lays out some of the findings.
What’s the Magic of Low-Carb Diets?
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Low-carb diets are powerful for weight loss, but even the people who all agree that they work can’t agree on precisely why they work. Is it only because eliminating a food group automatically forces you to eat fewer calories, thus bypassing all the ways that humans are terrible at calorie-counting and tricking you into eating a low-calorie diet without realizing it? Or is it actually via hormonal pathways that affect physiological drivers of fat storage?
You might say it doesn’t matter – if it works, it works, and who cares why? But the answer does actually have consequences, and luckily, it’s been studied – quite a bit, actually.
Low-carb vs. Low-fat Diets with Equal Calories
One way to test the question would be to put two groups on a diet with equal calorie content, but have one group eat low-carb and the other just restrict calories. If low-carb diets cause weight loss for some reason other than strict calorie restriction, then the subjects in the low-carb group should lose more weight despite eating the same number of calories.
This meta-analysis looked at exactly that: studies of isocaloric low-carbohydrate vs. balanced (whole grains, low-fat, the typical Food Pyramid type of diet) diets. The weight loss achieved by both diets was basically similar, on average:
There was no difference between the average weight loss of all the people eating low-carb diets and all the people eating low-calorie diets at either time point. Basically the same thing was true in diabetics: people with diabetes had lower average weight loss across the board, which didn’t differ between low-carb and other diets when calories are held constant.
This suggests that it’s really the calories, not the hormonal effects of a low-carb diet that matter. But hang on for a second and take a look at another review.
Unmeasured Low-Carb vs. Calorie Counting
The 2014 review above only included studies in which calories were roughly equal. A 2009 systematic review of randomized controlled trials that compared low-carbohydrate and low-calorie diets, without specifying that calories had to be equivalent (most of the low-carb diets didn’t actually specify calories at all, just carbs). The review looked at studies that lasted between 6 months and 1 year, and concluded that low-carbohydrate diets were overall more effective for weight, HDL, trigs, and systolic blood pressure, and that they were generally easier to stick to.
So how did two reviews of the evidence come to opposite conclusions? Probably because they have only one study in common: otherwise, they compared completely different studies. The 2014 review excluded studies where the low-carb subjects got to eat as many calories as they wanted, which took out most of the studies in the 2009 review. In most of the studies from the 2009 paper, the subjects in the low-carb group ended up eating slightly fewer calories than the subjects in the other groups.
For the rest of the story, head over to the source: