Low carb paleo diets have been all the rage during the past few years, advocating that people consume lower levels of carbohydrate as well as the fats from meats, chicken skin and even butter as the perfect way to shed body fat.
However, the paleo path has always been controversial, stirring up a persistent argument about whether low fat or low carb diets are the best way to shed our unwanted kilograms.
Now, a 12-year study from the National Institute of Diabetes and Digestive and Kidney Diseases ( NIDDKD)in the United States has provided definitive proof that low fat diets help people lose more body fat than low carbohydrate diets.
Published in the latest issue of the scientific journal Cell Metabolism, the comprehensive study collated data from dozens of controlled feeding and nutritional research conducted around the world to show that restricting dietary fat can lead to greater body fat loss than carb restriction, even though a low-carb diet reduces insulin and increases fat burning.
Dr Kevin Hall – a physicist turned metabolic researcher at NIDDKD – has worked since 2003 to bring together as much data as possible about how different nutrients affect human metabolism and body weight and to use this data to build mathematical models.
These models indicated that lowering fat would beat lower carbohydrate but there was no hard human data to back it up.
He and his team confined 19 consenting adults with obesity to a metabolic ward for a pair of 2-week periods, over the course of which every morsel of food eaten was closely monitored and controlled.
Each day, the researchers measured how much fat each participant ate and burned and used this information to calculate the rate of body fat loss.
At the end of the two dieting periods, the mathematical model proved to be correct. Body fat lost with dietary fat restriction was greater compared with carbohydrate restriction, even though more fat was burned with the low-carb diet.
However, over prolonged periods the model predicted that the body acts to minimise body fat differences between diets that are equal in calories but varying widely in their ratio of carbohydrate to fat.
“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,” Hall, who also cautions it is still too early to say conclusively which diet is better for you over the long term.
“Our results showed that, actually, not all calories are created equal when it comes to body fat loss.
“We are trying to do very careful studies in humans to better understand the underlying physiology that will one day be able to help generate better recommendations about day-to-day dieting. But there is currently a gap between our understanding of the physiology and our ability to make effective diet recommendations for lasting weight loss.”
Hall recommends that for now, the best diet is the one that you can stick to. His lab will next investigate how reduced-carbohydrate and reduced-fat diets affect the brain’s reward circuitry, as well as its response to food stimuli.
He hopes these results might reveal why people respond differently to different diets.
