The seemingly endless debate on low carb vs low fat caloric restriction diets in the context of weight loss is, in my opinion, fueled by 1. mixed anecdotal claims and arguments, 2. psuedoscience, and 3. mixed emprical evidence. As for the latter, key design and methodological limitations such as small sample sizes, heterogenous subject pools, relatively short term treatment periods, or poorly monitored free-living protocols introduce issues that may certainly confound the interpretation of the data and leave us with no real emprical consensus on the topic. Keep in mind however these limitations are quite understandable given the logistics that go into conducting these types of dietary intervention studies. Recently, one of the most comprehensive studies examining this debate was published in JAMA. This study assessed and compared weight loss, RMR, and other measurements in 609 overweight participants undergoing a lower carb or lower fat caloric restriction diet across a whole year. The retention rate for this study was one of the best I've seen in studies of this size and magnitude. The caloric intake was equivalent between the two groups at 3-month time points and results showed that after a year there were no significant differences in total weight loss, body fat %, or RMR suppression between the two diet interventions. These findings suggest, with decently strong evidence, that caloric deficit via caloric restriction is the main driver of weight loss in overweight individuals. It is my opinion that skewing macronutrient composition, at least for dietary carbohydrate and fat, is more practically relevant and perhaps impactful for those already with "healthy" body weight or body composition who are looking to cut a bit more body fat. Next up: are there genetic predispositions to specific diet responsiveness?