Trimming the Fat on Fat Loss

Low-fat diets may be more effective at generating fat loss than low-carb diets

Low-carb and low-fat are hot words when it comes to losing weight. But which diet really comes out on top in the battle of the bulge?

Researchers from the National Institutes of Health (NIH) found that low-carb diets may burn fat faster, but low-fat diets may actually result in more overall fat loss.

"A lot of people have very strong opinions about what matters for weight loss, and the physiological data upon which those beliefs are based are sometimes lacking," said principal study author Kevin Hall, PhD, a physicist and metabolic researcher at the National Institute of Diabetes and Digestive and Kidney Diseases, in a press release. "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."

Dr. Hall began his research by developing computer models of how different nutrients affect human metabolism and body weight.

These models showed that, despite some diet claims, a low-fat diet would lead to greater body fat loss than a low-carb diet.

Dr. Hall and team then conducted a controlled feeding study of 19 obese adults who were confined to a hospital ward for two two-week periods.

Everything these participants ate was closely monitored and measured.

In the first two-week period, these participants ate 30 percent fewer calories by restricting carbs. Their fat consumption remained the same.

In the second, fat was restricted while carb consumption remained the same.

Dr. Hall and team measured how much fat each participant burned on a daily basis.

Those on the low-fat diet lost more total body fat than those on low-carb diet.

However, according to Dr. Hall, diet composition might not make that much difference over the long term.

"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," Dr. Hall said. "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."

Dr. Hall cautioned that this was a lab experiment and should not be used to develop a real-life diet plan.

This study was published in the August issue of the journal Cell Metabolism.

The National Institutes of Health and the National Institute of Diabetes and Digestive and Kidney Diseases funded this research. No conflicts of interest were disclosed.