A recently published clinical trial out of Stanford University found that high-quality low-fat and high-quality low-carbohydrate diets could be equally effective for weight loss.
It was a positive finding from a well-designed study.
Many news headlines about the study, however, focused on something else entirely: that calories don’t matter for weight loss. Some examples:
The problem is: The study didn’t really find that.
In the trial, approximately 600 overweight and obese adults were randomly assigned to one of two diet groups (low-fat or low-carbohydrate) and followed over a 12-month period. During the study, participants attended regular nutrition classes where emphasis was placed on healthy, high-quality foods – such as whole grains, healthy fats, and minimally processed foods.
Participants were not specifically instructed to lower their calorie intake.
A couple of things.
First, calorie counting was not a subject of study of the trial. Clinical trials are designed to assess very specific things. Because calorie counting was not something one group in the study did and another group in the study did not do, no conclusions can be made about its possible impact – or lack of impact – on weight loss. Any headline implying otherwise is reaching beyond the findings of the current study.
Of course, diet quality is important. A largely plant-based diet that focuses on fruits, vegetables, whole grains, and healthy fats has long been shown to lower the risk of many diseases and help with weight control.
But diet quantity is key. To lose weight, we need to take in fewer calories than we expend – whether we count them or not.