If you happen to keep up with nutrition news, you’ve most likely come across numerous headlines this week that, once again, proclaim low-carb the king of weight loss diets. The low-carb vs. low-fat debate has been going on for nearly two decades now but, not surprisingly, media outlets were quick to report on this study funded by the National Institutes of Health and published in the Annals of Internal Medicine earlier this week.
A little background on the study
The purpose of the experiment was to compare the effects of a low-carbohydrate diet with a low-fat diet both on body weight and heart health. The 150 racially-diverse participants, all of whom were obese, were randomly divided into two groups: a low-carb group and a low-fat group. The low-carb group was directed to eat 40 grams or less of carbohydrates per day while the low-fat group was told to take in less than 30 percent of their calories from fat, which aligns with the recommendations from the 2010 Dietary Guidelines. The participants were not given calorie goals to adhere to however the two groups had comparable average calorie intake at the end of the trial.
When you scan the abstract, the weight loss results seem pretty clear cut. After 12 months, approximately 80 percent of participants had completed the trial. Participants following the low-carb diet saw significant decreases in weight loss, body fat, and certain markers associated with cardiovascular risk compared to those on the low-fat diet.
But before you start to divvy up your 40 grams of daily carbs, let’s dive deeper into some notable details that weren’t included in the abstract.
1. The low-carb diets weren’t nearly as low-carb as you think. As mentioned above, low-carb dieters were instructed to eat less than 40 grams of carbs per day; however, the average carb intake for the entire group ranged from 93 grams per day at the six month mark to 127 grams at 12 months, over 300 percent more carbs than the target amount assigned at the beginning of the study. (I don’t know about you but this definitely leaves me wondering about the sustainability of a 40 gram carbohydrate diet.)