Low-fat diet more effective than low-carb diet for losing body fat

When it comes to weight loss, opinions are divided as to what the best diet is for reducing body fat.

To investigate, a team of researchers compared a low-fat diet with a low-carbohydrate diet, finding that cutting fat intake resulted in greater body fat loss.


During this short-term study, a low-fat diet led to the greatest overall body fat loss.

The small but precise study, published in Cell Metabolism, assessed the weight loss of 19 obese adults who were confined to a metabolic ward for two 2-week periods.

Kevin Hall, a metabolism researcher at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), states that many people have strong beliefs about what matters for weight loss, yet the data these opinions are based upon are sometimes lacking.

"I wanted to rigorously test the theory that carbohydrate restriction is particularly effective for losing body fat since this idea has been influencing many people's decisions about their diets," he explains.
Unfortunately, there are many difficulties that researchers can experience when attempting to monitor how effective a particular diet is. Ensuring that participants stick to meal plans accurately and are truthful in self-reporting can be tricky to achieve.
By keeping the study participants on a ward, however, the researchers were able to control and record precisely what was being eaten.

The participants were admitted to the metabolic ward for two separate dieting periods. During the first, 30% of the participants' baseline calories were cut solely by restricting carbohydrates while fat intake remained the same. In the second period, 30% of baseline calories were cut by restricting fat intake while carbohydrate intake was unaffected.

Body fat loss was calculated by measuring the difference between daily fat intake and net fat oxidation while participants were inside a metabolic chamber.

With a mathematical model, Hall hypothesized that the low-carb diet would lead to changes in the amount of body fat burned by the body and that the low-fat diet would result in the greatest overall body fat loss.

'Not all calories are created equal when it comes to body fat loss'

At the end of the study, Hall's hypothesis was found to be accurate. Although more fat was burned when participants were following the low-carb diet, more body fat was lost during the low-fat dietary period.

"There is one set of beliefs that says all calories are exactly equal when it comes to body fat loss and there's another that says carbohydrate calories are particularly fattening, so cutting those should lead to more fat loss," states Hall. "Our results showed that, actually, not all calories are created equal when it comes to body fat loss, but over the long term, it's pretty close."

The mathematical model suggests that over a longer period, the body will act to reduce body fat differences between diets that contain equal amounts of calories, regardless of their carbohydrate-to-fat ratios.

In addition to the small number of participants involved in the study and its short duration, the researchers also acknowledge that their research is limited by the fact that the experimental design of the diets and the strict control of food intake is unrealistic in free-living individuals.

As such, the researchers were unable to address whether it would be easier to follow a low-fat or a low-carbohydrate diet in real-life situations. Hall believes that the best diet is the one that an individual can stick to. However, he concludes that there is still a lot of research that needs to be done.



Source:http://www.medicalnewstoday.com/articles/298172.php. author James Mcintosh

Reference:Calorie for calorie, dietary fat restriction results in more body fat loss than carbohydrate restriction in people with obesity, Kevin D. Hall et al., Cell Metabolism, doi: http://dx.doi.org/10.1016/j.cmet.2015.07.021, published online 13 August 2015, abstract.