Eligible Participants
- Generally healthy adults, 18-50 years of age
- Overweight or obese
Study Design
Sixty-one participants were randomized into four groups—two classes of low-fat (LF) and two classes of low-carbohydrate (LC) diet, with approximately 50% insulin resistant and 50% insulin sensitive participants in each class for 6 months. Throughout they study, they attended 14 one-hour classes led by a registered dietitian. Participants were instructed to cut back their total fat or digestible carbohydrate intake to 20 g per day, with the goal to achieve the lowest level of fat or carbohydrate intake within the first 8 weeks. They then slowly added fats or carbohydrates in increments of 5 to 15 g per week until they reached the lowest level of intake they believed could be maintained indefinitely. There was an emphasis on the quality of the diet and to prioritize nutrient-dense, whole foods. Change in weight was assessed at the beginning and end of the study.
Conclusions
Participants, overall, experienced substantial weight loss after 8 weeks —an average of 20 pounds— which represented 9% of their baseline weight. However, there was no significant interaction between diet assignment and insulin status for weight loss. These findings suggest that matching the diet to the individual’s insulin resistance status did not lead to increased weight loss success. The opportunity to detect a significant difference could have been limited by the focus on high diet quality for both diet groups and sample size.