Low-fat or Low-Carb, Which Works Best for Weight Loss?
A new study tackles whether it’s really true that a low-carb diet leads to more weight loss than a low-fat diet.
For the past few years, the majority of health experts have advised that a low-carb diet works better than a low-fat diet for weight loss. This is based on the reasoning that by eating fewer carbohydrates, the human body has lower levels of insulin, which in turn leads to increased fat being released from the body's stores and burned away. This was supported by an Annals of Internal Medicine study last year that found that when a low-carb diet group was pitted against a low-fat diet that the low-carb group lost about 12 pounds over the year and the low-fat group about 4 pounds.
However, a new study published in the journal Cell Metabolism found that from a metabolic viewpoint where every bit of food eaten, every minute of exercise logged and every breath taken, that low-fat actually wins out over low-carb.
In the study, 19 obese participants were confined to a metabolic ward where their diets and activity levels could be tightly controlled as a low-carb group was pitted against a low-fat group. During the first few days, all participants were placed on a 2,700 calories per day diet to set a baseline; after which, for the next 6 days, the participants were divided into low-fat/low-carb groups that were provided with meals that were identical in their final calorie count.
In the metabolic chamber, by monitoring the amount of oxygen and carbon dioxide being breathed out and the amount of nitrogen in each participant’s urine, the researchers were able to calculate precisely the metabolic processes taking place inside their bodies. Knowing this allowed the researchers to be able to calculate body fat loss with each participant as the difference between daily fat intake and net fat oxidation measured while confined within the metabolic chamber.
What the data showed was that the carbohydrate-restricted diet led to sustained increases in fat oxidation (as previous studies have shown) and a loss of approximately 53 grams of body fat per day. However, on a fat-restricted diet the amount of fat oxidation was unchanged, yet the low-fat diet participants lost approximately 89 grams of fat per day—significantly more than the low-carb group participants!
Their results appear to support the current notion that not all calories are the same. However, when the study’s data was placed under some mathematical model simulations that took time into consideration, the simulations predicted that fat loss differences between a low-carb diet over a low-fat diet will likely even out in the long run contrary to what was observed over just 6 days. In other words, both diet types if followed will eventually lead to near-equal weight loss. Therefore, choosing one diet over the other is more dependent upon which type of diet an individual is more likely to stick with in the long run.
For additional info on whether you are following a low-carb or a low-fat diet, here are some related health articles to help you lose that weight:
Reference: “Calorie for Calorie, Dietary Fat Restriction Results in More Body Fat Loss than Carbohydrate Restriction in People with Obesity”; Cell Metabolism July 2015; Kevin D. Hall et al.