A new study has concluded that people lose more weight when they go on a low-fat diet than when they go on a low-carb diet.
Dietitians and nutritionists have long tried to decide on which helps people more, but consensus seems hard to find. Several studies have investigated the matter since the 1980s. Most of the ones in the 80s and the 90s favored low-fat diets, but studies conducted this past decade have favored low-carb diets. Until now that is.
A team of researchers from the National Institutes of Health (NIH) decided to conduct their own study, and chose to take an unusual approach with it. PhD Kevin Hall, metabolism researcher from the National Institute of Diabetes, Digestive and Kidney Diseases, gave a statement informing that he and his colleagues wanted to test the low-carb theory.
This theory says that low-carb diets are better because they decrease a hormone known as “insulin”, which is responsible for regulating fat tissue. Lowering insulin levels supposedly gives you a fat-burning edge, but PhD Hall was curious to see how an obese body adapts to receiving less carbs vs how it adapts to receiving less fat.
The research team took 19 obese adults and checked them into the NIH clinical center. They all had roughly the same body mass index (BDI) and weight, and had every ounce of food and second of exercise prescribed and monitored by the research team for the duration of their stay.
PhD Hall explained that unless researchers “do the kind of study that we have done here, where we basically lock people up for an extended period of time, control everything, and make sure we know exactly what they eat…then we don’t have the kind of control that’s required to answer these really basic questions”.
The subjects had to spend two (2) weeks at a time at the clinical center. Researchers gave them a typical diet of 2.740 calories per day – 50 percent (50%) carbs, 35 percent (35%) percent fat, 15 percent (15%) protein – for the first five (5) days of each stay.
For the next six (6) days, the researchers gave subjects either a low-carb diet or a low-fat diet. Each of these diets had 30 percent (30%) less calories than the initial one. They also asked subjects to spend an hour per day exercising on a treadmill during this period.
The final step of the experiment was to put subjects in metabolic chambers (climate-controlled rooms sealed from all the rest and connected to several devices that recorded and analyzed the changes that the subjects were going through) for the next five (5) days.
The researchers then looked at everything from the subjects’ metabolite levels and hormone levels, to how much nitrogen and carbon dioxide they were releasing into the air, and concluded that the low-fat diets are more efficient than the low-carb diets.
Test results showed that the subjects who had been put on a low-fat diet lost an average of 463 grams, whereas the ones who had been put on a low-carb diet only lost an average of 245 grams during the six (6) days from the second faze.
However, the research team did stress that their study relied on strictly controlling the subjects’ food intake, which is not a very feasible approach with “free-living individuals”.
The findings were published in the medical journal Cell Metabolism.
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