For years dieters were told that a calorie is a calorie, but a new study from Boston Children’s Hospital suggests people may burn more calories on a low-carb diet than on a diet rich in carbohydrates.
The new study did not focus on losing weight, but rather on a factor that makes it hard to maintain a weight loss: The fact that the body adapts as pounds are lost by slowing metabolism, which results in fewer calories being burned. And for most people that means weight is regained.
A theory, known as the carbohydrate-insulin model, suggests that increases in the consumption of so called high-glycemic foods – which raise blood sugar sharply right after they’re eaten - trigger hormonal changes that increase hunger and lead to weight gain.
To see if metabolism and hunger can be shifted by types of foods people eat, the researchers enlisted 164 overweight adults aged 18 to 65 who had already lost 10 percent of their body weight, and randomly assigned them to one of three carb-varying diets for five months.
The volunteers’ meals, provided by the researchers, had the same daily calorie count and all contained 20 percent protein. But one group’s diet consisted of 20 percent fat and 60 percent carbs, another got a diet with 40 percent fat and 40 percent carbs and the third group ate 60 percent fat and 20 percent carbs.
Lowest carb dieters had higher daily energy expenditure
After tracking the volunteers’ weight and measuring energy expenditure through the study period, it was clear that those who had consumed the lowest levels of carbs had burned the most calories. As well, their levels of the hunger-regulating hormones, ghrelin and leptin, were lower too.
Volunteers in the low-carb group burned 209 to 278 calories a day more than those on the high-carb diet, which meant they were burning 50 to 70 calories more a day for every 10 percent decrease in carbs to their total energy intake.
The volunteers with the highest insulin secretion at the start of the study had an even more dramatic difference in energy expenditure: those on the low-carb diet burned as much as 478 calories a day more than those consuming the highest level of carbs.
This kind of extra calorie burn would translate “into about 20 pounds of weight loss in a year among those on the low carb diet compared to those in the high carb group,” the lead researcher said
While most studies look at inducing weight loss, this one is about weight maintenance to determine if there a particular macronutrient composition that can result in a higher calorie burn?
Keep in mind that whole a low-carb diet may help calorie burning, so can resistance training.
Source: The BMJ, online November 14, 2018.
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