This is the basic principle of nutrition: when it comes to weight loss, all calories are equal. No matter what you eat, the key is to keep track of your calories and burn more than you consume.
But a large new study published on Wednesday in the BMJ magazine provokes conventional wisdom. It was found that adult overweight people who cut carbohydrates from their child and replaced them with fat increased the metabolism rapidly. After five months of eating, their bodies burned about 250 calories more per day than people who were eating high-carbohydrate foods, suggesting that limiting carbosens can help people ease weight loss.
A new study is unlikely to end decades of debate about the best diet for weight loss. But it gives strong new evidence that all calories are not metabolically similar to the body. And suggests that popular weight loss tips promoted by health authorities – count calories, reduce the size of the portion and reduce fat intake – may be outdated.
"This study confirms that, in particular, the diet is higher in starch, and sugar changes the rate of body burn after losing weight, reducing metabolism," said Dr. Dariush Mozaffarian, dean of Friedman's School of Nutrition and Food Science at Tufts University, who was not involved in the research. "The observed metabolic difference was large, more than enough to explain the effect of io-io, which was often experienced by people who are trying to lose weight."
Dr. Mozaffarian called the conclusions "deep" and said that they are contrary to the conventional wisdom of counting calories. "It's time to move the guidelines, government policy and industrial priorities from calories and low fat and towards a better quality of nutrition."
The new study is partly unique because of its size and rigor. It is one of the largest and most expensive research ever undertaken on the topic. The researchers recruited 164 adults and fed all their daily meals and snacks for 20 weeks, with close monitoring of their body weight and numerous biological measures. The trial cost $ 12 million and was mostly supported by a grant from the Science Initiative for Science, and a non-profit research group founded by Geri Taubes, a scientific and health journalist and advocate of low carbohydrates. The study was also supported by funding from the Nev Balance Foundation, the National Institute of Health and others.
While some experts praised the findings, others were more cautious. Dr Kevin Hall, a scientist and obesity expert at the National Institute for Diabetes and Diseases of Digestive and Kidney Diseases, said the new study was ambitious and very good. But he said that the researchers used methods that asked questions about the results. One method used to track metabolism, dubbed double-labeled water, has not been shown to be reliable in people with low carbohydrate content and may have exaggerated the amount of calories that fired the subjects, he said.
Dr David Ludvig, endocrinologists at Harvard Medical School and the Boston Children's Hospital and one of the study authors, disagreed, saying: "We have used a gold standard method that has been validated in a wide range of experimental conditions and universally adopted on the ground."
Dr. Hall added: "I would like it to be true that there was a diet combination of carbohydrates and fats that led to a large increase in energy consumption – and I really hope that it is true. But I think there are reasons to question whether it is or not. "
The idea that calorie counting is the key to weight loss is already embedded in government guidelines for a child. It is the driving force of public health policy, such as mandatory counting of calories in restaurant menus and food labels. Many experts say that the main cause of the obesity epidemic is that Americans eat too much calories of all kinds, which is caused by easy access to cheap and very tasty foods and that they need to exercise control. on the For example, the National Institutes of Health encourage people to count calories and warn that fat in the diet has more calories per gram of protein or carbohydrates: "You need to limit fat to avoid additional calories," it says.
But experts such as Dr. Ludwig argues that the obesity epidemic is driven by refined carbohydrates like sugar, juices, bagels, white bread, pasta and highly processed cereals. This food has a more expensive blood sugar and insulin, a hormone that promotes the storage of fat and they can increase appetite. Dr. Ludwig and his colleague Dr. Cara Ebbeling has published studies suggesting a child with different carbohydrate and fat relationships, but identical amounts of calories have very different effects on hormones, hunger, and metabolism. He also wrote the best-selling book on nutrition with lower carburate.
Dr Hall and others disagree. Studies have been published that challenge the idea that food-restricted carbine-bound drugs accelerate metabolism and fat loss. Dr. The Hall said that low-carb foods have many benefits: they can help people with type 2 diabetes to manage their blood sugar levels, for example. But he argues that the explanation of carbohydrates and insulin for obesity is too simplified and "experimentally falsified" in rigorous studies.
Last year Dr Hall published a meta-analysis of nutritional studies that suggest that energy costs are actually slightly higher on low amounts of fat. Ali Dr. Ludwig pointed out that these studies were very short, lasting longer than a month and for a maximum of a week or less. He said that the low-carb content adjustment process could last a month or longer.
"For a few days or weeks, there is not enough time to make any meaningful conclusion on how the diet affects metabolism over a longer period," he added.
To do a new study, Dr. Ludwig and his colleagues collaborated with the Framingham State University, about 20 miles outside of Boston, where they recruited students with overweight, staff members, and faculty members. Each participant went through two stages of the study. They were first placed on a strict child who reduced body weight by about 12 percent, which was designed to emphasize their metabolism.
"At that moment, their bodies are trying to regain weight," said Dr. Ludwig. "It pushes the body and predisposition to regain weight."
In the second phase of the study, subjects were assigned to one in three children with 20%, 40% or 60% of their calories from carbohydrates. Protein kept steadily at 20 percent of calories in each diet.
Over the next five months, the researchers carefully tracked objects and provided them with enough daily meals and snacks to prevent them from losing or gaining weight. This was so that researchers can accurately determine how the metabolism of a subject responds to different children until their body weight remains stable.
The researchers were tracked by biomarkers who helped them ensure that participants put their diets on. They also worked with a large food service company, Sodeko, to prepare thousands of healthy meals that the subjects could eat in the cafeteria or take them home. A typical meal for a high-angle group can consist of a chicken burrito bowl with rice and vegetables, for example, or a fried turkey with a bean and a potato potato. A low carbohydrate group would get a similar ration with less carbohydrates, such as frozen chicken salad or fried turkey with green beans and mashed carfiol.
What the researchers found was striking. About 250 additional calories burned by subjects in a low-carb content group every day can potentially lose weight of 20 kilograms after three years of eating, said Dr. Ludwig. People who have had the tendency of high-level insulin secretion have done the best on low-carbohydrate diet, burning about 400 extra calories per day.
Subjects on a low-carbine-containing diet also had the fastest decline in the hormone called stomach-derived greens. Ghrelin Promotes hunger and body and reduces energy costs. Suppression of greens can be one of the reasons why low-carbohydrate diet has increased metabolism, authors point out.
Dr. Ludwig emphasized that the results should be replicated by other researchers and emphasized that the findings do not endanger whole fruits, beans and other unprocessed carbohydrates. Instead, he said, the study suggests that reducing foods with added sugar, flour and other refined carbohydrates can help people maintain weight loss by increasing their metabolism at lower body weight.
"It seems that this food is undermining your metabolism," he said. "Slow down metabolism in a way that can work for long-term maintenance of weight loss."