In 2018, Dr. Christopher Gardner of Stanford University partnered with the US National Institutes of Health, The Nutrition Science Initiative, and a team of nutrition experts to conduct one of the biggest weight loss studies to date. The study assigned 609 participants to one of two diets, low-fat or low-carb, for a 12 month period. The participant breakdown was 263 males and 346 females that were free of major health conditions, with an average BMI of 33, and an average age of 40±7 years.
Over the first two months of the study, each group was instructed to consume at most 20g of the macronutrient (carb or fat) they were designated to restrict. After the two-month period each participant could start adding fats or carbs to their diet until they reached the lowest possible intake they could sustain. On average, the low-fat group consumed 42 g of fat per day, and the low-carb group consumed an average of 96.6 carbs per day.
Neither group received a recommended daily caloric intake, however they were instructed to consume high-quality whole foods and drinks that minimized sugar, refined flours, and trans fats. They were to eat as many vegetables and as few processed foods as possible.
After the trial concluded, 481 participants remained. On average, participants lost 11-13 pounds. The study showed no significant weight-loss differences between the low-fat and low-carb groups. Both groups improved their BMI, body fat %, waist circumference, blood pressure, and fasting insulin and glucose levels with no significant differences betwixt them.
This study further contributes to the ever-growing mountain of research that suggests when caloric intake and protein intake are consistent between diets, the proportion of carbs or fat is not a significant variable for weight loss. Furthermore, the behavioral information generated from participants in both groups suggests that it is incredibly difficult for most people to actively sustain an extremely low-carb or low-fat diet. Alas, both diets can work for weight loss. The right diet that will work for you is the one you can adhere to sustainably and consistently. Simply transitioning to a whole-food, minimally processed diet with a lot of vegetables and enough protein is a solid first step in developing eating habits that can last for life!
Study Link: https://pubmed.ncbi.nlm.nih.gov/29466592/